POSIVA OY

POSIVA 2000-08

Engineering rock mass classification of the Olkiluoto

investigation site

Kari Aikas (editor)

Annika Hagros

Erik Johansson

Hanna Malmlund

Ursula Sievanen

Pasi Tolppanen

Saanio & Riekkola Consulting Engineers

Henry Ahokas

Eero Heikkinen

Petri Jaaskelainen

Paula Ruotsalainen

Pauli Saksa

Fintact Oy

.June 2000

Maps: ©Maanmittauslaitos permission 41 /MYY/00

Mikonkatu 15 A. FIN-001 00 HELSINKI, FINLAND

Phone (09) 2280 30 (nat.). (+358-9-) 2280 30 (int.)

Fax (09) 2280 3719 (n;:Jt \ t ... ~"'R-Q-1 ??Rn ~710 ti.->+ \

Posiva-raportti - Posiva Report

Posiva Oy Mikonkatu 15 A, FIN-001 00 HELSINKI, FINLAND Puh. (09) 2280 30 -lnt. Tel. +358 9 2280 30

1 ekiJa(t)- Author(s) TOimeksiantaJa(t)- Commissioned by

Kari Aikas, Annika Hagros, Erik J ohansson, Hanna Malmlund, Ursula Sievanen, Pasi Tolppanen, Henry Ahokas, Eero Heikkinen, Posiva Oy Petri Jaaskelainen, Paula Ruotsalainen, Pauli Saksa

N1meke- 11t1e

Raportin tunnus - Report code

POSIV A 2000-08 Julkaisuaika - Date

June 2000

ENGINEERING ROCK MASS CLASSIFICATION OF THE OLKILUOTO INVESTIGATION SITE

Tiiv1stelma - Abstract

Olkiluoto in Eurajoki is being investigated as a possible site for the final disposal of spent nuclear fuel from the Finnish nuclear power plants. The selection of the depth, placement and layout of the repository is affected by the constructability of the bedrock. The constructability, in turn, is influenced by several properties of the host rock, such as its lithology, the extent of fracturing, its hydrogeological properties and rock engineering characteristics and also by the magnitude and orientation of the in situ stresses and the chemistry of the groundwater. The constructability can be evaluated by the application of a rock classification system in which the properties of the host rock are assessed against common rock engineering judgements associated with underground construc­tion. These judgements are based partly on measurements of in situ stresses and the properties of the bedrock determined from rock samples, but an important aspect is also the practical experience which has been gained during underground excavation in similar conditions and rock types.

The aim of the engineering rock mass classification was to determine suitable bedrock volumes for the construction of the repository and has used data from the site characterization programme carried out at Olkiluoto, which consisted of both surface studies and borehole investigations. The classification specifies three categories of constructability - normal, demanding and very demanding. In addition, rock mass quality has also been classified according to the empirical Q-system to enable a comparison to be made.

The rock mass parameters that determine the constructability of the bedrock at Olkiluoto depend prin1arily on the depth and the lithology, as well as on whether construction takes place in intact or in fractured rock. The differences in the characteristics of intact rock within a single rock type have been shown to be small. The major lithological unit at Olkiluoto, the mica gneiss, lies in the normal category of constructability to a depth of 500 m. At greater depths the level of constructability decreases, due to increased levels of in situ stress. The most important factor that is likely to determine the location and the lateral extent of a repository at Olkiluoto is the presence of particular fracture zones.

Ava1nsanat- Keywords

nuclear waste, final disposal, constructability, rock mass, classification, Q-system, Olkiluoto

ISBN ~~~N

ISBN 951-652-094-4 ISSN 1239-3096

Sivumaara - Number of pages Kieli - Language 145 English

Posiva-raportti - Posiva Report

Posiva Oy Mikonkatu 15 A, FIN-001 00 HELSINKI, FINLAND Puh. (09) 2280 30 -lnt. Tel. +358 9 2280 30

Tekija(t)- Author(s) Toimeks1antaja(t)- Commissioned by

Kari Aikas, Annika Hagros, Erik J ohansson, Hanna Malmlund, Ursula Sievanen, Pasi Tolppanen, Henry Ahokas, Eero Heikkinen, Posiva Oy Petri Jaaskelainen, Paula Ruotsalainen, Pauli Saksa

Nimeke- Title

Raportin tunnus - Report code

POSIV A 2000-08 Julkaisuaika- Date

Kesakuu 2000

OLKILUODON KALLIOPERAN LUOKITTELU LOPPUSIJOITUSTILOJEN RAKENNETTAVUUDEN KANNALTA

T1iv1stelma- Abstract

Eurajoen Olkiluodon kallioperaa tutkitaan yhtena vaihtoehtoisena loppusijoituspaikkana Suomen ydinvoimalaitosten kaytetylle polttoaineelle. Loppusijoitusvaraston sijoitussyvyyteen, sijaintiin ja pohjaratkaisun muotoon vaikuttaa kallioperan rakennettavuus. Rakennettavuus puolestaan riippuu useista kallioperan ominaisuuksista kuten kivilaji-, rakoilu- ja hydrogeologisista ominaisuuksista, kallion jannitystilasta, pohjavesikemiasta ja kallioteknisista ominaisuuksista. Rakennettavuutta voidaan arvioida luokittelumenetelmalla, joka perustuu kalliotilaa ymparoivan kalliomassan ominai­suuksien kokemusperaiseen arviointiin. Tama voi perustua osittain esimerkiksi jannitystilan ja kivinaytteiden mittaustuloksiin, mutta erityisesti se perustuu kalliorakentamisesta saatuihin kaytan­non kokemuksiin.

Taman rakennettavuusluokituksen tarkoituksena on osoittaa Olkiluodon kallioperasta loppusijoitusti­lojen rakentamiseen soveltuvat alueet. Kalliomassa luokitellaan kolmeen rakennettavuusluokkaan: normaaliin, vaativaan ja erittain vaativaan luokkaan. Vertailukelpoisuuden vuoksi esitetaan myos kansainvalisesti tunnettu NGI-luokitus (Q-luku). Luokittelu perustuu Olkiluodon alueella tehtyihin karakterisointitutkimuksiin, jotka kasittavat maanpinta- ja reikatutkimuksia.

Useat kallion rakennettavuuteen vaikuttavat luokitusparametrit nayttaisivat riippuvan selvimmin siita, kuuluuko tarkasteltava kalliotilavuus kiinteaan kallioon vai rakoiluvyohykkeeseen, seka kallion sijaintisyvyydesta ja kivilajista. Kiintean kallion kivilajikohtaiset laatuerot tutkimusalueen sisalla nayttaisivat vahaisilta. Suoritetun kallioluokituksen perusteella Olkiluodon paakivilaji, kiillegneissi, kuuluu rakennettavuudeltaan normaali-luokkaan noin 500 m syvyyteen asti. Tata syvemmalle tiloja sijoitettaessa rakennettavuuden arvioidaan vaikeutuvan empiirisen NGI-luokituksen perusteella, johtuen kallioperassa vallitsevasta jannitystilasta. Tarkeimpia loppusijoitustilojen asemointia vaaka­suunnassa rajoittavia tekijoita ovat eraat hydrogeologisesti tai kallioteknisesti merkittavat rakoiluvyo­hykkeet.

Avainsanat- Keywords

ydinjate, loppusijoitus, rakennettavuus, kallio, luokittelu, Q-luku, Olkiluoto kalliopera

l~tlN ISSN ISBN 951-652-094-4 ISSN 1239-3096

::i1vumaara- Number ot pages Kieli - Language 145 Englanti

PREFACE

Teollisuuden Voima Oy (TVO) and Fortum Power and Heat Oy prepare for the final disposal of the spent nuclear fuel in the Finnish bedrock. The site of the final disposal facility will be chosen by the end of the year 2000. Posiva Oy, which is jointly owned by the two nuclear power companies, manages the final disposal task and the investiga­tion and development work.

The rock classification that has been processed in this report is a part of the work of the PARVI-project. The purpose of the classification is to locate the rock volumes which are suitable for construction of final disposal repository in the investigation site of Olkiluoto. Similar rock classification has been made also for the investigation sites of Romuvaara, Kivetty and Hastholmen (reports are in Finnish). This report is a modified translation from the Posiva Working Report 99-55 (in Finnish).

Sections 1, 3, 4.1.1, 4.1.2, 4.1.3, 4.1.5, 4.1.6, 4.2.1, 4.2.4, 4.3.3, 4.4.1, 4.4.2, 4.4.4, 4.5, 4.7, 4.8, 5 and 6 of this report have been written at Saanio & Riekkola Consulting Engi­neers. Sections 2, 4.1.4, 4.2.2, 4.2.3, 4.2.5, 4.3.1, 4.3.2, 4.4.3 and 4.6 have been written at Fintact Oy. The compiling of this report has been made at Saanio & Riekkola. The translation of the report has been made by Ursula Sievanen of Saanio & Riekkola Con­sulting Engineers and Pirjo Hella of Fintact Oy. The revision of the English language has been made by Dr Tim McEwen of QuantiSci, UK. He also made many useful re­marks to the text.

TABLE OF CONTENTS

ABSTRACT

TIIVISTELMA

PREFACE

1

1 INTRODUCTION ........................................................................................ 3

2 BEDROCK MODEL OF THE OLKILUOTO SITE ....................................... 5 2.1 General .............................................................................................. 5 2.2 Litho logical model .............................................................................. 8 2.3 Structural model ............................................................................... 13 2.4 Block model ..................................................................................... 16

3 ESTIMATION OF THE CONSTRUCT ABILITY ........................................ 27 3.1 General ............................................................................................ 27 3.2 Rock mass classification parameters ............................................... 31 3.3 Constructability classes ................................................................... 33 3.4 Spatial distribution of the constructability in the bedrock ................. 41

4 ROCK MASS CLASSIFICATION ............................................................. 43 4.1 Litho logical properties ...................................................................... 43

4.1.1 Mineral composition ....................................................................... 43 4.1.2 Degree of foliation .......................................................................... 44 4.1.3 Grain size ...................................................................................... 45 4.1.4 Degree of weathering ..................................................................... 46 4.1.5 Strength and deformation properties .............................................. 48 4.1.6 Thermal properties ......................................................................... 51

4.2 Fracture properties .......................................................................... 53 4.2.1 Fracture directions ......................................................................... 53 4.2.2 Fracture frequency ......................................................................... 54 4.2.3 Trace length ................................................................................... 58 4.2.4 Frictional properties ....................................................................... 61 4.2.5 Fracture width ................................................................................ 65

4.3 Hydrogeological properties .............................................................. 69 4.3.1 Hydraulic conductivity of the intact rock ......................................... 69 4.3.2 Hydraulic conductivity of the A-structures ...................................... 71 4.3.3 Water ingress and grouting properties ........................................... 7 4

4.4 Structural rock type .......................................................................... 77 4.4.1 General .......................................................................................... 77 4.4.2 Intact, fractured and crushed rock types ........................................ 77 4.4.3 Hydraulically-conductive rock type ................................................. 80 4.4.4 Constructability .............................................................................. 81

4.5 In situ stresses ................................................................................. 82 4.5.1 Principal stresses ........................................................................... 82 4.5.2 Strength/stress ratio ....................................................................... 84

2

4.6 Groundwater chemistry .................................................................... 86 4.6.1 General .......................................................................................... 86 4.6.2 pH values ....................................................................................... 86 4.6.3 Sulphate content ............................................................................ 86 4.6.4 Free carbon dioxide ....................................................................... 88 4.6.5 Ammonium content ........................................................................ 88 4.6.6 Magnesium content. ....................................................................... 89 4.6.7 Chloride content. ............................................................................ 89 4.6.8 Radon content ............................................................................... 91

4. 7 Rock engineering properties ............................................................ 92 4.7.1 Drillability ....................................................................................... 92 4.7.2 Blasting properties ......................................................................... 93 4.7.3 Crushing properties ........................................................................ 94 4.7.4 Requirement for rock support ......................................................... 94

4.8 NGI classification (Q value) ............................................................. 98 4.8.1 Determination of the Q value ......................................................... 98 4.8.2 Rock quality according to Q value ................................................ 1 03

5 DISCUSSION AND CONCLUSIONS ..................................................... 117

6 SUMMARY ............................................................................................. 127

REFERENCES ............................................................................................... 131

APPENDIX 1: Distribution of frictional properties of fractures in structures .... 139

APPENDIX 2: The measured hydraulic conductivities of the A-structures ..... 143

3

1 INTRODUCTION

The current disposal concept for spent nuclear fuel (Figure 1-1) consists of a facility on the surface and an underground repository excavated in the bedrock below it. It is proposed to construct three vertical shafts, one of which could be replaced by an access tunnel, to connect the surface facilities to the underground repository. The present repository design includes a central access tunnel connected to deposition tunnels, with surface facilities located in the vicinity of the shafts. It is proposed to encapsulate the spent fuel in copper canisters which will have a diameter of about 1 m and a height of either 3.6 m or 4.8 m (depending on the type of spent fuel). The canisters will be emplaced in vertical disposal holes bored into the floors of the deposition tunnels. The diameter of these disposal holes is about 1.7 m, the depth 6.6 or 7.8 m (again depending on the type of spent fuel) and the spacing of the holes approximately 7.5- 8 m. The space between the copper canisters and the rock will be filled with bentonite and the deposition tunnels will be filled with a mixture of crushed aggregate and bentonite. Following disposal the repository, including the shafts and the possible access tunnel, will be filled with crushed aggregate and bentonite, and the upper part of the shafts will be sealed with massive plugs of reinforced concrete.

The location depth and the final layout of the repository will depend on the geological, hydrogeological, hydrochemical and rock mechanical conditions at depth. In this report the bedrock characteristics of the Olkiluoto investigation site are described and classi­fied using a rock mass classification system. The aim of the work is to provide an esti­mate of the constructability of the bedrock, so that initial plans can be developed as to how the location and design of the repository can be adapted to the site conditions.

The classification of the bedrock is based on the data obtained from the site investiga­tions and on the 3D bedrock model developed for the Olkiluoto site. The site investiga­tions consisted of both surface-based studies and measurements in and between bore­holes. An important aspect of the classification is the practical experience gained from previous underground excavation in similar rock types. For the sake of comparability the internationally known NGI classification (the Q-system), which is commonly used in rock engineering, was also made.

Before the construction of a repository could take place at Olkiluoto more detailed underground investigations would need to be carried out. The most significant part of these investigations would be performed in a research shaft and/or tunnel which is planned to be excavated.

Canister transfer shaft

Deposit ion tunnel

4

11--++-- Personal shaft

Figure 1-1. Basic design for the high level nuclear waste disposal facility.

5

2 BEDROCK MODEL OF THE OLKILUOTO SITE

2.1 General

The bedrock model describes the rock types and the more densely fractured zones and illustrates the geometry and properties of the rock types and fracture zones of the bed­rock. The model presents what is currently considered to be the most likely description of the rock mass, based on the knowledge gained from the investigations to date.

The bedrock model is based on the results of field surveys and on the interpretations and expert judgement of the results and consists of two submodels - the lithological model describing the rock types and the structural model describing the fracture zones. The structures are divided into different classes, according to the level of confidence as­cribed to them, and into different types, according to their overall properties. The bed­rock model is compiled using the computer-aided geological ROCK-CAD modelling system (Saksa 1995). It provides a visualisation of the rock mass for the planning of further investigations and for the interpretation of the field surveys. The groundwater flow and hydrochemical models are both based on the geometrical and property infor­mation contained within the bedrock model. The bedrock model also represents a cen­tral source of information for the rock mass classification presented in this report.

The bedrock model of the Olkiluoto site has a surface area of about 35 km2, which

includes a substantial area beneath the sea (Fig. 2.1-1). The volume of the modelled rock mass is greater than 50 km3 and the model extends to a depth of 1500 m. The legend and notation used in the model are presented in Figure 2.1-2. The classification of the rock mass is, however, limited to the volume of the rock covered by the surface and borehole investigations. These cover an area of 6 km2 and include that part of the Island of Olkiluoto lying west of the investigation boundary (Fig. 2.1-1 ). It is currently proposed to construct the repository for spent nuclear fuel in the central part of the Island of Olkiluoto, approximately in the area shown in Figure 2.2-1. The classification of the rock mass is based on version 3.0 of the lithological model (Saksa & Lindh 1999) and on version 3.0 of the structural model (Saksa et al. 1998). The models include the results and interpretations of the investigations carried out in boreholes KR1 - KR10.

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Figure 2.1-1. Surface map of the Olkiluoto bedrock model.

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7

OLKILUOTO BEDROCK MODEL CLassiFication and graphical description Structure

T~pe DirectL~

Text LabeL observe

Open or

~ more abundant XX

Fracturing

Fracture zone XX 9 Major fracture 11 zone XX C>R i I I I or ;.Rp2)

Crushed zone @

ROCK TYPES ~~ HIGMATITIC MICA GNEISS L____j I MGN I

EJ TONALITIC GNEISS ITONGNI

~ TONALITE/GRANODIORITE L_Lj ITONI

OVERLAY NOTATIONS

~ GRANITE/PEGMATITE ~lGR/PGI

~ MYLONITE/MYLONITIZATION ~[EYJ

OTHER ANNOTATIONS

rr BOREHOLE

Ll' PLANNED BOREHOLE

fl PERCUSSION DRILLING

EP MULTILEVEL PIEZOMETER

~ KA e DRILLED WELL

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Certaint~ class Probable Possible

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LJ LOCATION OF CROSS SECTION

~ STRIKE AND DIP '-..-'Oo

~~~ BOUNDARY OF INVESTIGATION AREA TOPOGRAPHY

SHORELINE 2M <= Z <= 4H 6M <= Z <= BM 10M <= Z <= 18M

24-HAY-OOr ... oLki/Legend_i win 0 210 0 297

Figure 2.1-2. Legend and notation used in the Olkiluoto bedrock model.

8

2.2 Lithological model

The lithological model is based on the results of geological mapping of outcrops, air­borne geophysical survey, magnetic surface mapping and other regional geophysics which are described in Anttila et al. (1999). The cored boreholes and the two investiga­tion trenches provide extensive information on lithological contacts and fracture zones and on variation of the rock properties as a function of depth. Surface lithological maps of the site are shown in Figures 2.1-1 and 2.2-1 and the distribution of rock types at a depth of 500 m in Figure 2.2-2. The occurrence and location of the rock types in the central part of the investigation volume is shown in Figure 2.2-3.

The lithological model describes the lithological units and their distributions. The bed­rock is heterogeneous and prediction of the precise locations of any particular rock type within the rock mass is difficult (Laine 1996). The surface extent, extension to depth, dip and dip direction of many rock types are uncertain. Evidence from core material does not seem to suggest a correlation between lithological contacts and fracture zones and the majority of the contacts do not show degrees of fracturing or weathering greater than those found in the more homogeneous parts of the intact rock. The majority of the formations dip towards the south-southeast, and this trend is paralleled by several fracture zones.

The dominant rock type at the site is migmatitic mica gneiss (MGN), although veined gneiss (VGN), which is a strongly migmatitic mica gneiss, dominates its southern part. The diffuse contact between the mica gneiss and its veined counterpart runs to the south of boreholes KR2 and KR3 and probably dips gently to the southeast, thereby con­forming to the large-scale lithological trend. Typically, the gneisses are foliated with the foliation trending east-northeast and dipping to the south-southeast at 50 - 60°.

A group of tonalite gneiss (TONGN) bodies has been mapped and interpreted within the veined gneiss host rock. In the lithological model their extension to depth is assumed to be the same as their longest dimension on the surface and, based on borehole observa­tions, the units seem to be narrowing with depth. They are either steeply dipping or have a moderate dip to the southeast-southwest. In addition, tonalite gneiss bodies dipping gently and moderately to the northeast have been inferred. The modelled geometry of the units is uncertain. Their surface extent and extension to depth have been deduced from the integration and interpretation of all the surface and borehole data. Examples of such tonalite gneiss bodies are provided by the ones intersected in borehole KR8 over the depth interval of 210- 242 m and in borehole KR9 close to the surface.

Elongated bodies that are tonalitic and granodioritic in composition (TON/GRDR) have been observed in the northern part of the Island of Olkiluoto, close to the shoreline and partly beneath the sea. In this report these are referred to as tonalite (TON). They are assumed to extend to depths of a few hundred metres and to dip gently to the south­southeast. It is possible, that these tonalites belong to an overturned fold structure or that they are separate parallel dykes. The tonalites observed in borehole KR5 over the depth intervals of 174- 255 m and 324- 385 m could represent different parts of the same folded body.

9

Granite/pegmatite (GRIPG) units are mainly located in the central part of the investiga­tion area. Their strike conforms with the general structural trend from west-southwest to east-northeast and, typically, the dip of the various units is in the range of 50- 75° to the southeast. In the model the larger masses of granite/pegmatite in the central part of the site have been extended to only 50 m depth, because information from local boreholes does not indicate the presence of a uniform, continuous granite/pegmatite body at greater depths. When considering other, smaller granite/pegmatite bodies, the assump­tion has been made that their extension to depth is the same as their shortest surface dimension.

One single diabase dyke (DB) is located in the central part of the island. Its dip and dip direction, about 75° to north-northwest, have been interpreted from the magnetic surface measurements and differ from the major geological trend. A minor body of amphibolite (AFB/MDB) has been mapped as an inclusion in the area of Santalahti. It is modelled as a steeply dipping body, which thins with depth and extends tentatively to a depth of 200 m. Other occurrences of amphibolite or metadiabase have been observed in bore­hole KR2 over depth intervals of 731 - 7 43 m and 881 - 885 m, as well as in borehole KR7 over the depth interval of 169- 172 m. The only occurrence of mylonite (MY) is in borehole KR4 where 3 m of it are present.

10

Figure 2.2-1. Surface map of lithology and structures from the central part of the investigation area. Structures in class "certain" are shown. Traces of the unexposed subhorizontal structures are displayed with dashed lines.

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Figure 2.2-2. Occurrence of rock types, fractures and major fracture zones at a depth of500m.

12

Figure 2.2-3. South-north vertical cross section through the Olkiluoto site scale model. Boreholes KR2, KR4, KR6 and KRJ 0 lie in the section and the rock types and fractured sections present in these boreholes are shown. View towards the east.

13

2.3 Structural model

Most of the volume of the site bedrock model consists of sparsely fractured intact rock. The portions of the rock mass, which have been fractured or crushed and lie in zones, are assumed to be fracture zones and are described as structures. Various types of structures (i.e. fracture zones) are present. The model contains 30 structures, each of which is described in Saksa et al. (1998) and labelled as R+number structures. In addition to these, the model contains other and more uncertain structural features. The interpreted R -labelled structures form less than 10 % of the volume of rock modelled. It is, however, important to know their locations, orientations and properties in order to be able to plan the location of the repository and to model the ground water flow system.

The locations and properties of the structures have been modelled with the help of several investigation methods, including cored boreholes and hydraulic testing, as well as geophysical surface and borehole measurements. The fracture zones have been classified into different types based on their overall properties and on what is known about each zone. The thickness of the structures ranges from a few metres to some tens of metres, they extend for distances which are typically of the order of hundreds of metres and are assumed to be continous and planar. On many occasions intact parts of the bedrock lie within the modelled structures.

The structures have also been divided into four types (open or more abundant fractur­ing; fracture zone; major fracture zone and crushed zone) based on their fracturing properties. Zones with a poorly understood geometry and a low fracture density belong to the class of open or more abundant fracturing. They consist of at least one hydrauli­cally-conductive open fracture. Fracture zones contain abundant fracturing in classes Rill-Ill and have weathering in classes Rp0-1 according to the Finnish Engineering Geological Rock Classification (Korhonen et al. 1974). The structural model contains 19 fracture zones. A major fracture zone contains crushed rock (RiiV) or its degree of weathering is above Rp2, the fracture frequency is greater than 10 fractures/m and fractures are filled or open. At present the model contains 11 such structures. Some major fracture zones are composed of several components, some of which could be classified independently as fracture zones. A crushed zone is the most intensively frac­tured and weathered type of structure and contains abundant portions of clay material (RiV). Regional structures have been labelled with the notation AR+number. They have been classified according to the same principles as those applied in the site scale model. In this study they are only encountered close to the boundaries of the bedrock model.

Structures have also been classified into four classes, according to what is know about them and according to the number and type of observations, as certain, probable, possible and other. A structure belonging to the directly observed (certain) class is one identified by direct observation (outcrop, drill core) at least at one location. A structure in the probable class is one that has been observed by two or more indirect methods, for example from the interpretation of geophysical surveys or lineament investigations. If different investigation methods have provided evidence for the existence of such an indirectly-observed structure and, in addition and according to expert judgement, such a structure is likely to exist, the structure is placed in the certain class within the bedrock model. A structure in the possible class includes structures deduced from one indirect

14

method of investigation. The class other has been used to incorporate uncertain geomet­ric features or alternatives into the model, which can be useful during the development of the model and during the planning of subsequent investigations. The majority ( 19) of the structures are evidenced from direct observations, eight structures lie in the probable and three in the possible category. There are additional structures in the other category, but they are not considered in this context. Table 2.3-1 lists the data associated with the intersections of these structures in the boreholes and investigation trenches.

Geometrical data on the structures - such as their extension, dip direction and dip - are frequently based on the interpretation of indirect measurements, derived mainly from seismic reflection (VSP) surveys, borehole radar measurements, electrical cross-hole surveys or pumping tests. The greatest uncertainties are related to the extension and ori­entation of the structures. Thirteen of the structures are steeply dipping (dip> 60°), al­most the same number (12) have inferred moderate dips between 30- 60° and five are gently dipping (dip< 30°). The main dip direction is towards the southeast. In addition to the structures which are currently defined, additional fracture zones may be present, based on the evidence of fracture intersections in boreholes. In some cases the investi­gation methods used have not been able to determine the geometry of such putative structures and they are referred to by RX -labels in the model.

The surface maps of the model illustrating the lithology and the structures are shown in Figures 2.1-1 and 2.2-1. A horizontal cross section at a depth of 500 m is shown in Figure 2.2-2. Figure 2.2-3 shows a vertical north-south cross section through the central part of the island. The varying dips of the structures, as well as their dominant dip towards the south and southeast can be seen. Figures 2.2-1 and 2.2-3 also show the locations and outlines of some structures which do not crop out in the area of the model.

During the interpretation and modelling phase an alternative description for structures R17 A-B and R20A- F was developed. It was considered that, together, these struc­tures could be interpreted to form a discontinuous multicomponent zone with a width of approximately 30- 70 m, with the possibility that the various components of the zone could vary in orientation (Front et al. 1997, Saksa et al. 1998). Structure R17C was not, however, considered as belonging to this alternative zone, but has in all cases been considered to be a separate structure.

15

Table 2.3-1. The intersections between the R-structures of the Olkiluoto bedrock model and the boreholes and investigation trenches. The dip direction, dip and true (perpen­dicular) thickness at the intersections are also presented.

Structure I Borehole/ Upper Lower Dip direct- Dip Thickness trench contact (m) contact (m) ion e) (0) (m)

Rl I KR1 847 850 171 50 2.4

I KR5 405 410 171 50 4.5 I KR6 216 220 171 50 3.4

R2 KR5 253 271 170 69 12.8 R9 c KR3 157 162 130 56 4.2

A 386 397 125 50 9.8 Bl KR5 275 283 120 72 4.7

RlO ~I KR1 514 542 160 60 19.8 764 773 153 50 7.4

Cl KR3 115 131 140 55 13.4 Dl KR5 120 127 140 55 5.9

Rll I

KR1 106 112 140 50 4.9 TK2 0 2 140 50 1.3

R12 I I KR6 126 136 46 45 0.9

R13 KR1 636 646 126 87 2.6 Rt4 r:R2 ---·4o5 -·-------·-4o7-----··-·----75-···--·--·-··--···65--·--···-·-·······-·-·-o:7··-·-····--···

-:!~ --~ -::-----llr----E------~-----!!------~1:~-B I KR10 367 370 160 20 2.8

R19 I

KR4 80 85 180 5 5.0 KR7 82 84 180 5 1.9

I KR8 80 84 180 5 3.4 -·-·-·-·-·----r--------------··-----··-----···----------·----·-··-·-·-··-··----·-···--·-··-·-··-·············-.. ··-·····-·-··-··----·-·-···· R20 A

I KR4 310 316 170 10 6.0

B

I

366 371 170 11 5.0 c KR7 225 240 170 10 14.4 D 278 289 170 10 10.6 E I KR9 442 447 170 30 4.9 F I 471 481 170 30 9.8 A i KR10 260 272 170 10 11.8 I B I 326 328 170 10 2.0

R21 I

KR1 613 618 160 22 5.0 KR2 597 615 160 22 17.7

I I KR4 757 795 160 22 37.3 ! KR5 467 476 160 22 9.0

R24 I KR8 105 140 149 48 10.0 I KR9 147 151 149 48 3.4 I TK1 0 2 149 48 0.6

R26 I KR1 106 112 180 10 4.9 I KR2 73 75 180 10 2.0 I i KR5 76 79 180 10 2.9 I KR10 126 129 180 10 3.0

R30 I KR9 545 550 155 35 4.7 i

16

2.4 Block model

The bedrock at Olkiluoto was divided to blocks in order to estimate the spatial distribu­tion of the level of constructability. These blocks are subvolumes of the bedrock which are bounded by structures considered to be significant from the point of view of rock engineering or hydrogeology (Saksa et al. 1998). Blockwise analysis of the bedrock properties provides an insight into the spatial variation of the factors used in determin­ing the constructability. The bedrock model of the Olkiluoto site was the starting point for the division of the bedrock into blocks. The principle of this division into blocks is illustrated in Figure 2.4-1 and, in order to carry out this division, a new method of analysis and a computer program was developed (Nummela 1998).

The structures bounding the blocks are listed in Table 2.4-1. The depth range of block analysis is from the surface to a depth of 1000 m. The goal of block division was to develop a block model so that there would be sufficient data from each block to estimate the constructability of the block and allow comparisons to be made between the blocks. The block analysis covers the area of the Island of Olkiluoto and, in addition to the R -structures of the bedrock model, the northern shoreline of the island is used to bound the analysed volume. In the block model the shoreline is described by the special structure "R1-boundary". Ten blocks were defined as a result of the block division and the properties of the blocks are presented in Table 2.4-3. Block 3, which is bounded by the structure R9 and the extension of the structure R17-20, was combined with block 2 and thus forms the northeastern part of block 2. The combination of the two blocks is justified, because the structure R 17-20 in reality does not extend northwest of structure R9. If blocks 2 and 3 had not been combined, block 3 would have been small and there would have been no borehole information available within it. The locations of the blocks at the surface, at a depth of 500 m and on vertical cross sections through the

Figure 2.4-1. Illustration of a block and its bounding structures (Nummela 1998).

17

boreholes are presented in Figures 2.4.2 - 2.4-8. A three dimensional visualisation of the block model is shown in Figure 2.4-9.

When evaluating the dependence of the constructability on different rock parameters, the properties of the bounding structures were not included in determining the properties of the blocks. The properties of the internal structures within the blocks (e.g. fracture zones included within the blocks) were either analysed separately or included in the properties of the blocks, depending on the parameter. The location of the structures in different blocks is presented in Table 2.4-2.

Table 2.4-1. Structures bounding the blocks and their significance.

Structure Geotechnical I Hydrogeological significance significance

I (Transmissivity at 500 m

depth (m2/s))

R1 significant I significant (8E-7)

R3 significant

I significant (lE-5)

R5 significant significant (lE-5)

R7 not significant

I significant (lE-5)

R9B-C not significant not significant (6E-8)

R17-R20 partly significant I significant (lE-5)

R21 significant I significant (8E-7)

Table 2.4-2. Location of structures in the blocks.

Block/ Structures Structures completely Structures partly Structure bounding the block intersecting the block intersecting the block

Block 1 RI, R5, R2I R8, R29 R22, R23 ----·---·-·----------~-- ·-·----·---·------·-·-·--·····-··-···- ~~----·---····---·-·------..-~----·------···-··--··-·-··------·---··-·

Block 2 RI, R5, R9, R2I R2, R29 R6, R8, R9A, RIOA, RI3, R22, R23

Block 4 RI, R3, R5, R7, R9, R6, R13, R29 RIO, RII, RI2, RI6, RI8,

RI7-20 RI9,R22,R24,R26,R29 - ---

Block 5 RI, R3, R5, R9, R6, RlOD, Rll, RI3, R14,

RI7-20, R2I RI6,RI7C,RI8,R29,R30

Block 6 RI, R2I R29 R2, R8, R22, R23 ·-------·-!------·-----·----- ·-------~------...... -------~----·-·----·-..-.--····-· ··--·---··-·--·--·--·~·-··-·-····-·················--·····-··--····--·---·-··----··

Block 7 RI, R9, R2I

Block 8 RI, R3, R5, R9 RIO, RI3

Block 9 RI, R3, R2I

Block 10 RI, R2I RI3, RI5

18

Table 2.4-3. Properties of the blocks of the Olkiluoto model.

Block/ Borehole Volume Range Distribution of Property intersections (m) (m3·106

) X, Yand Z rock type ( o/o)

Block 1 KR5 410-467 110 X:6792748- 6793518 Mica gneiss 62 %

Y:1523237- 1525602 Tonalite 38 %

Z:-421- 0

Block 2 KR3 162- 502 420 X:6791919- 6793196 Mica gneiss 68 %

KR5 283-405 Y:1523464- 1525527 Tonalitic gneiss 10%

Z:-764- 0 Tonalite 20 %

Granite 1 % ·--·-->---

,, ___ .... ____ !------·----·-·-··-----·-·--·--·--· • -·---·-···~---··,._.-.... ·-·· .. ···-----·-..... -.h ...........................

Block 4 KR1 0-212 738 X:6791460- 6793308 Mica gneiss 82 %

KR2 0-218 Y:1524536- 1527724 Tonalitic gneiss 7 %

KR3 0- 157 Z:-568- 0 Tonalite 2%

KR4 0-310 Granite 9%

KR5 0- 120

KR6 0- 175

KR7 0-225

KR8 0-254

KR9 0-442

KR10 0-260 -~-·

Block 5 KR1 212- 613 952 X:6791502- 6793222 Mica gneiss 91 %

KR2 225-597 Y:1524783- 1527727 Tonalitic gneiss 4 %

KR4 371 - 757 Z:-1 000- -54 Tonalite 5%

KR5 120-275

KR6 175-216

KR7 289- 301

KR9 481 - 601

KR10 328-614

Block 6 KR1 850- 1001 901 X:6792307 - 6793498 Mica gneiss 96 %

KR5 476-559 Y: 1523260- 1525895 Tonalite 4%

Z:-1000- -20

Block 7 KR1 773- 847 164 X:6791899- 6792874 Mica gneiss 95 %

Y:1523860- 1525530 Tonalitic gneiss 5 %

Z:-1000- -276 ----·------- ----------.--·· ... -· ... ·-~--..-·-- -----··----~- .. --.. ......................................... -... ..... ~ ................ ~ ..... -...-.~·-·---·---..... --. ----~--... ·----·-··-··· ........................ -. ....... _. .....................

Block 8 KR1 618- 764 336 X:6791559- 6792976 Mica gneiss 96 %

KR2 615- 880 Y:1525179- 1527660 Tonalitic gneiss 4 %

KR4 795-902 Z:-1000- -445

Block 9 KR6 220- 301 25 X:6792939- 6793353 Mica gneiss 58%

Y:1525533- 1526441 Tonalite 42 %

Z:-522- -87

Block 10 KR2 890- 1052 174 X:6792482 - 6793339 Mica gneiss 99 %

Y: 1525494- 1526834 Tonalite 1 %

Z:-1000- -331

19

Figure 2.4-2. Suiface map of the Olkiluoto block model. Boreholes, investigation trenches and structures in classes "certain" and "probable" are displayed.

If 11 11

" 11 11 11

20

Figure 2.4-3. Horizontal intersection of the Olkiluoto block model at the depth of 500m.

Z: 0

z~-soo

Block6

z.-1ooo

21

BlockS

BlockS

o-.

BlockS 250

R17~

Figure 2.4-4. Location of the blocks in a vertical cross-section through boreholes KRJ andKR2.

22

BlockS

250

BlockS

250

Figure 2.4-5. Location of the blocks in a vertical cross section through boreholes KR3 andKR4.

23

Z:

Z:-500

Block6

0. 250 BlockS

BlockS

Z:-500

Figure 2.4-6. Location of the blocks in a vertical cross section through boreholes KR5 andKR6.

24

Z:

// R29

11

Z:-500

BlockS

BlockS Oa 250

~ ~R?

r-)t X

1 .... 111-===--==-~250 )t X

Figure 2.4-7. Location of the blocks in a vertical cross section through bore holes KR7 andKR8.

25

R3 Block4

BlockS

0 • s 250

OLKR10

Figure 2.4-8. Location of the blocks in a vertical cross section through bore holes KR9 andKRJO.

26

Figure 2.4-9. Three dimensional visualisation of the block model. The vertical section through the model is oriented northwest-southeast and lies through boreholes KR3 and KR7. The view is from the southwest.

27

3 ESTIMATION OF THE CONSTRUCT ABILITY

3.1 General

In tunneling, the behaviour of a rock mass depends on the material properties of the rock, the number and properties of fractures and the magnitude and orientation of the in situ stress. In estimating the rock mass quality for the construction of a repository atten­tion must be paid also to the hydraulic properties of rock, the chemical composition of the groundwater and the rock's engineering properties. All those factors may vary con­siderably in a tunnel or excavation and there can, therefore, be a large range in rock mass conditions which will need to be considered during excavation.

Minor variations in rock conditions are not always necessary or even possible to con­sider in the design and construction of underground excavations. Due to the variable characteristics of rock masses, classification systems have been developed in order to encapsulate and simplify their essential properties and behaviour. Classification systems have normally been developed to describe the quality of the rock from a constructability point of view.

In rock mass classification systems the quality of a rock mass in terms of its constructa­bility is usually either defined qualitatively by describing the properties of the rock mass, or quantitatively, by developing an index which will define its level of quality in terms of specific numerical values of some of its properties. The former type of system includes, for example, the Finnish Engineering Geological Rock Classification system (Korhonen et al. 1974, Gardemeister et al. 1976), whereas the second includes classifi­cation methods that have been widely used internationally, such as RQD (Hoek & Brown 1982), the Q-system of NGI (Barton et al. 1974, Grimstad & Barton 1993) and the RMR system (Bieniawski 1976, 1989).

The rock quality index RQD is defined as the percentage of core recovered in intact pieces of 100 mm or more and can vary from 0- 100 %. The value of RQD is usually determined per metre of borehole. Its value is determined by the density of natural fractures and the extent of weathering. Core breaks caused by the coring technique or by handling of the sample are excluded. The rock quality designation in relation to its RQD value is shown in Table 3 .1-1.

Table 3.1-1. Rock quality according to RQD (Hoek & Brown 1982).

RQD-value Rock quality

<25% Very poor

25-50% Poor

50-75% Fair

75-90% Good

90- 100 o/o Excellent

28

In addition to the number of fractures and the extent of weathering, many other rock properties have an effect on rock constructability and therefore the RQD index alone cannot be considered as an adequate indicator of constructability. The RQD value is, however, often used to give an approximate indication of the rock quality, since it is very easy to define.

The rock mass ratio RMR is determined with the help of six rock variables which are the uniaxial compressive strength (score 0- 15), RQD value (3- 20), fracture spacing (5- 20), fracture quality (fracture length, width, roughness, fracture filling and weath­ering, with a combined score of 0 - 30), ground water conditions (0 - 15) and orientation of fracture sets (0 - 60). The RMR value is calculated as the sum of the scores of the rock variables and the corresponding rock quality is determined according to Table 3.1-2.

In the NGI classification system the rock quality Q (Table 3.1-3) is determined using six rock variables (equation 3.1-1), which are its RQD value (range 10- 100), joint set number In (0.5 - 20), joint roughness number Ir (0.5 - 4), joint alteration number I a (0.75- 20), joint water reduction factor Iw (0.05- 1) and stress reduction factor SFR (0.5 - 400). The determination of the Q value is illustrated more precisely in Section 4.8.

Q _ RQD J, Jw ---·-·--

Jn la SRF 3.1-1

According to Hoek et al. ( 1995) the Q value can be converted into an equivalent RMR value using equation 3.1-2. The conversion is based on the comparison of cases in which the RMR value has been 85 or smaller.

RMR = 9 ln Q + 44 3.1-2

If the poor class in the NGI classification system (Q = 1 - 4) is converted with the help of equation 3.1-2 to the equivalent RMR rating, a value in the range 44- 56 will be obtained, which correspond to the fair class of the RMR system. This demonstrates that the RMR system provides an overestimate of rock quality compared with that given by the Q value.

Table 3.1-2. Rock quality according to RMR (Rock Mass Rating) system (Bieniawski 1976).

Rock quality/ Rock classes class I II Ill IV l V ·--·--·--·---·-·------- ______________ ... _ ........ _ .. _, _____ ......... - .......... ______ ,_, ___ .. ___ .............................. - ......... , ... __ , ......... i ... - ........................... - .................... .

RMR-value 100- 81 80- 61 60-41 40- 21 : ... 1 < 20 (score sum)

Description of rock quality

Very good Good Fair Poor Very poor

29

Table 3.1-3. Rock quality according to the Q-system (Barton et al. 1974).

Rock quality class Q value

A Exceptionally good 400 - 1000

Extremely good 100 - 400

Very good 40 - 100

B Good 10 - 40

c Fair 4 - 10

D Poor 1 - 4

E Very poor 0.1 - 1

F Extremely poor 0.01 - 0.1

G Exceptionally poor 0.001 - 0.01

The RMR rating and Q value differ most significantly from each other by the fact that, whereas the Q value includes the combined effect of the state of stress and the ground­water pressure, it does not take into account the orientations of fractures in relation to the direction of tunnelling. The RMR value is, however, influenced by this factor.

The Q value is quite a good measure of rock quality, but it pays attention neither to the groundwater chemistry nor to the rock engineering properties which will, however, affect the constructability of the repository. Rocks with different qualities with respect to tunnelling can have the same Q value, for example an intact rock under high stress conditions could have the same Q value as a fractured rock subjected to low stresses. This would mean that two rocks which had the same Q value could require different methods of excavation and rock support requirements.

The RMR rating measures the quality of a rock mass reasonably well, but it does not include the influence of the in situ stress, groundwater chemistry and rock engineering properties. Even though the RMR rating includes the effects of fracture orientations in relation to the direction of tunnelling, that particular attribute of the rating system could not be used in this classification work because the position and orientation of the deposition tunnels are not yet known.

The rock classification applied here is based mainly on experience and engineering judgement and was carried out in a transparent manner so that it was possible to determine which properties of the bedrock were most important in determining its constructability. In addition, the rock was also classified using the NGI system for the purposes of comparison. The NGI system was chosen because it is recognised internationally and because it takes into account the values of the in situ stress and the groundwater pressures, both of which are important attributes determining the con­structability of the rock mass. The Q value was also used in estimating the requirements for rock support. The aim of the rock classification was to provide a method for a systematic analysis of the information obtained from the site investigations from the point of view of constructability. The purpose was not to develop a new rock mass classification method.

30

The classification of the constructability of the rock mass in this report is based mainly on information obtained from cored boreholes, but the data obtained from surface investigations have also been used. In addition, the bedrock model has also been a useful source of data (Saksa & Lindh 1999, Saksa et al. 1998).

31

3.2 Rock mass classification parameters

The inclusion of rock properties within the classification system was determined em­pirically by their anticipated significance in relation to the constructability of the under­ground facilities. The following rock properties were selected for inclusion: 1) rock quality factors, 2) state of stress, 3) groundwater chemistry and 4) rock engineering properties. The classification parameters which describe these properties are shown in Table 3.2-1.

Rock quality was determined with the help of lithological properties, fracture properties and hydrogeological properties (Table 3.2-1). Besides these properties, the structural rock type, which describes rock quality with the help of its most significant quality fac­tors affecting the constructability, was defined (Table 3.2-2). The structural rock types, except hydraulically-conductive rock, i.e. intact rock, fractured rock and crushed rock, are mutually exclusive. They can all, however, be classified as hydraulically-conductive rock if their hydraulic conductivity K ~ 1E-8 m/s.

Table 3.2-1. The parameters used for the classification of the bedrock for the final disposal facility.

Rock quality factors State of stress Ground water Rock engineering chemistry properties

A. Lithological properties: -maximum - pH - drillability - mineral composition horizontal stress

- degree of foliation (O'H) - carbon dioxide - blasting properties - grain size (free)

- degree of weathering -minimum - crushing strength properties

horizontal stress - ammonium properties -- thermal properties

(ah)

- magnesium - requirement for

B. Fracture properties: - vertical stress ( O'v) rock support

- Number of principal fracture - sulphate directions - strength/stress-

- fracture frequency ratio (UCS/aH) - chloride - fracture length

- frictional properties - radon - fracture width

C. Hydro geological properties:

- hydraulic conductivity - groutability

- estimated groundwater ingress

I D. Structural rock type

32

Table 3.2-2. Structural rock types.

Structural rock type

Intact rock

Fractured rock

Description

- the lithological properties can vary freely, except weathering

- unweathered or medium weathered at most (Rp1-2)

- fracture density varies from sparse to abundant

- the fracture density of borehole core sample is less than 10 fractures/m

- the size of unfractured blocks of rock is at least 30 dm3

- the size of unfractured blocks of rock is less than 30 dm3

- the fracture frequency of the densest fracture set is more than 10 fractures per metre (valid at outcrops and in excavations)

- the fracture density of borehole core sample is more than 10 I fractures/m

1 -partially filled fractures ~-------------+------------·--·-·-----·--··-·-----·-·---·-

' - the size of unfractured blocks of rock is less than 30 dm3 Crushed rock

! - the fracture frequency of the densest fracture set is more than 10 I fractures per metre (valid at outcrops and in excavations)

! - the fracture density of borehole core sample is more than 10 I fractures/m

I -abundant clay fillings

! -strongly weathered rock (Rp2, Rp3) '-·------··-·---·-+-- ---·-·---··--------·-·-·-····-··

Hydraulically- I - intact, fractured or crushed rock with a hydraulic conductivity conductive rock I K;::: 1E-8 m/s

The parameters which describe the in situ stress in the rock are the maximum and minimum horizontal stresses and the vertical stress. However, the most important indi­cator from the classification point of view is the ratio of the uniaxial compressi ve strength (UCS) and the maximum horizontal stress ( crH) i.e. the strength/stress ratio.

The choice of chemical species for inclusion within the groundwater chemistry pa­rameter was based on those chemical factors which were known to affect the durability of concrete (Finnish Concrete Association 1992, Leinonen 1997). The exception was radon, which was included because its maximum allowable content in breathed air is limited by the Finnish Radiation Act (59211991).

Rock engineering properties, such as drillability, and blasting and crushing properties, depend to a great extent on the rock type. The extent of rock support required depends mainly on the level of fracturing, the rate of groundwater ingress, rock strength, and the magnitude and orientation of the in situ stress.

33

3.3 Constructability classes

The rock mass was classified with the help of those rock mass parameters which were believed to affect the constructability of the proposed deposition tunnels, and the level of constructability was placed in one of three classes: normal, demanding and very de­manding.

The normal class includes rock masses where the construction of the repository can be carried out by conventional hard rock tunnelling methods, using standard materials and assuming a high level of operational efficiency, whilst allowing for the high quality of construction required for the deposition tunnels. This would imply that a rock mass in this class would allow tunnels to be excavated by the drill and blast method using 4 - 5 m long rounds and that any rock support required with rock bolts and shotcrete could be carried out at some later time after the drill and blast work has been completed.

The demanding class includes rock masses where more sophisticated and expensive construction methods and materials would be required. The rate of tunnelling would be considerably reduced, compared with the rate associated with rocks in the normal class, or much effort would have to be placed on aspects of operational safety. Considering the example of blasting and rock support, this would mean that tunnels could be exca­vated by drill and blast using 3 - 4 m long rounds, but temporary rock support would be required after each round. In addition, pre-grouting could be required. Permanent sup­port could be supplied using rock bolts and thick shotcrete.

The very demanding class includes rock masses where much more sophisticated and expensive construction methods and materials would be needed. In this case the rate of tunnelling would be very much lowered or considerable effort would have to be placed on operational safety. Considering the example of blasting and rock support, this could mean that tunnels could be excavated by drill and blast using 1 - 3 m long rounds, but that the rock would have to be supported temporarily with bolts and shotcrete after each round. Also pre-support techniques and pre-grouting would be needed before excava­tion. Final support could consist of fibre-reinforced shotcrete with reinforced ribs or a cast concrete lining.

When describing the constructability of rock with the help of the classification used in this report, the rock parameters should always be selected according to the purpose of the classification. In the situation where a comprehensive classification is required, for example in the case of the design of the final facility, it should be developed using all of the possible classification parameters.

The lithological properties of the rock mass proposed for use in the classification of tunnels and shafts have been listed in Table 3.3-1. The mineralogy of the rock mass only seldom significantly complicates the constructability of rock in Finland. The most important exception to this is probably the situation where the rock has a significant content of clay minerals, which may have a noticeable effect on the requirements for a rock support system. A high content of quartz or mica may have a considerable effect on the drilling rate or the crushing properties. The degree of foliation, in particular if it is marked, is likely to make the boring of the disposal holes more difficult and will

34

result in a poorer hole quality, if the drilling direction is close to the direction of foliation. Grain size is likely to have its most noticeable effect on the drillability, especially during the full face boring of disposal holes, as rock strength often increases with decrease in grain size in crystalline rocks. At worst, rock types could be placed on the basis of foliation or grain size into the demanding class of constructability.

Weathering of the rock mass lowers its mechanical strength, but its hydraulic conduc­tivity may increase or decrease, and therefore the costs of rock support and possibly sealing will increase. The class limits have been set so that the differences in costs of construction of different classes will be significant. In rock which is completely weath­ered the construction costs may be several times those of the same unweathered rock. Class limits determined on the basis of strength correspond closely to the strength limits in the classification of Deere and Miller (in Hoek & Brown 1982) and to similar limits in the RMR classification. The thermal properties of rock usually do not affect its con­structability. However, in the case of spent fuel disposal, its thermal properties affect the space requirements for the repository and, thereby, the costs of construction because the separation of the disposal holes depends on the rock's thermal conductivity, KT (Raiko 1996). The limits of the constructability classes have been chosen so that differences between separate classes with respect to the required total length of deposition tunnels is about 10% (i.e. a decrease in the thermal conductivity KT of the rock of 0.5 W/mK would result in an additional 10% of deposition tunnels being required).

Table 3.3-1. Constructability classes according to lithological properties.

Lithological Normal Demanding Very demanding property/Class Mineral content ordinary rock - significant content of extremely significant

forming minerals clay minerals content of clay

- high content of micas minerals

- high content of hard minerals

Degree of foliation non-foliated- strongly foliated

moderately foliated ---Grain size fine - coarse very fine-grained

Degree of weathering un weathered or medium weathered medium to completely slightly weathered rock (Rp2) weathered rock (Rp2-3) rock (Rp0-1)

Strength properties crucs ~ 100 MP a aucs =50- 100 MPa crucs <50 MPa

Thermal properties KT>2.5 W/mK KT= 2.0-2.5 W/mK KT< 2.0W/mK

35

The classification of the frictional properties of fractures in the rock mass is defined in Table 3.3-2. The presence of three main fracture sets is considered normal in Finnish bedrock and an increase in the number of fracture sets from that number increases the costs of excavation and rock support. The classification of fracture frequency was based on RQD values, so that the RQD classes fair, good and excellent were combined to represent the normal class in terms of constructability, the RQD class poor was equated with the demanding class and the RQD class very poor with the very demanding class. In the classification of fracture trace lengths and fracture widths use was made of the RMR classification system (Bieniawski 1989) and the same class limits were defined. The classification of frictional properties was made with the help of the Jr and la parameters of the NGI classification system. In this case the class limits were estimated using expert judgement.

The hydrogeological properties of rock mass can be determined on the basis of the measurements carried out in boreholes. The extent of ingress of groundwater into tun­nels can be estimated when the average hydraulic conductivity of rock mass, the groundwater pressure and the dimensions of a tunnel are known (e.g. equations 4.3-1 and 4.3-2). The groutability can be estimated on the basis of the hydraulic conductivity and the extent of fracturing. The classification of groundwater ingress (Table 3.3-3) is based on engineering judgement. The class limits relating to values of the hydraulic conductivity and the groutability were estimated by calculating the hydraulic conduc­tivities corresponding to the class limits for the volumes of inflowing groundwater. In estimating the class limits for groutability, attention was also paid to the results of the Strip a Project (PolHi et al. 1994) concerning the dependence between groutability and hydraulic conductivity.

Table 3.3-2. Constructability classes according to the extent and properties of the fracturing.

Fracturing property/ Normal Demanding Very demanding Class Number of fracture 1 - 3 4 5 or more sets

Fracture frequency RQD =51- 100 RQD = 26-50 RQD = 0-25 -~

Fracture length <5m 5- 10 m > lOm ----- ------·~----------------------

Frictional properties 1r=4.0-1.5 Jr = 1.0 Jr = 0.5 (roughness I a= 0.75 - 3.0 I a= 4.0- 8.0 Ja = 10.0- 20.0 alteration, friction

<I>~ 15° 15° ~<I>~ 7° <I>< 70 _angl_e) -- ------~------ -------------·-·-----·-· ·~------·u.-ouoo-uon-•u•~•h~-uouo .. o--~--•-• Fracture width no filling or hard hard filling > 5 mm soft filling > 5 mm,

filling < 5 mm or soft filling < 5 mm especially swelling clay

36

Table 3.3-3. Constructability classes in the depth range 300 - 700 m according to the rock's hydrogeological properties.

Hydrogeological Normal Demanding I Very demanding

__ pr~-e_~_!y /Cl_~~---···--·--- ··----·----·--·---··--··-··---·-- I ··------··-·--·····-·--·-·······-·--·-·······--······-r···--······-····-·······-····-················-·····--···-· Hydraulic - K < 1E-9 m/s - K = 1E-9- 1E-8 i - K > 1E-8 m/s j

conductivity m/s f

l i - none or few l - many

hydraulically- - several i hydraulically-conductive fractures hydraulically- I conductive

conductive fractures I fractures

Estimate of grouting - tight rock, no rock, that is I rock that is very

requirements and grouting needed difficult to grout, ! difficult to grout !

properties (K:::;; 1E-9 m/s) but which can be i (i.e. K > 1E-8 grouted to achieve a I m/s after - hydraulically-

I

conductive rock value of grouting)

which can be grouted 1E-8 m/s ~ K > to achieve a value of 1E-9 m/s

i K:::;; 1E-9 m/s)

Estimated <5 5-20

I > 20

groundwater ingress (1/min/100 m tunnel) !

The classification of structural rock types (Table 3.3-4) is based partly on the Engi­neering Geological Rock Classification (Korhonen et al. 1974) and partly on experience gained from rock engineering projects. Hydraulically-conductive rock would be placed in the normal class if its proportion per 100 m tunnel were so small that the total groundwater ingress were less than 5 1/min, and correspondingly into the demanding class if ingress were in the range 5 - 20 1/min. If the ingress exceeded 20 1/min, the rock would be placed in the very demanding class.

Table 3.3-4. Constructability classes on the basis of Q values and structural rock type.

Property /Class Normal Demanding Very demanding

Intact rock non-foliated - strongly foliated: moderately foliated: tunnels and shafts tunnels and shafts

Fractured rock tunnels and shafts

Crushed rock tunnels and shafts

Hydraulically- tunnels and shafts, tunnels and shafts, tunnels and shafts, conductive rock, when ingress when ingress is when ingress

(ingress of < 5 1/min/1 00 m 5- 20 1/min/100 m > 20 1/min/100 m

groundwater in 1/min/100 m tunnel)

Q value 1000- 1 1-0.04 <0.04

37

The class limits that have been set for the Q value in Table 3.3-4 are based on signifi­cant changes in rock support, and thus in terms of costs, of a tunnel of the same size as the deposition·tunnels. In the normal class rock bolting and, if necessary, thin shotcrete are likely to be sufficient. In the demanding class it is assumed that temporary support with fibre-reinforced shotcrete, and permanent support with thick fibre-reinforced shot­crete and bolting will be needed. In the very demanding class, pre-bolting, temporary support with fibre-reinforced shotcrete, and permanent support with fibre-reinforced shotcrete and reinforced ribs of shotcrete and bolting or a cast concrete lining are likely to be required.

The classification of strength/stress ratios (Table 3.3-5) is based on empirical observa­tions from hard rock engineering projects (Grimstad & Barton 1993). When the ratio is > 5 usually normal rock support is sufficient. Locally, temporary support may be needed in addition to the permanent support, mainly for requirements of operational safety. When the ratio is 3 - 5 systematic temporary support, in addition to permanent support, is usually needed. When the ratio is < 3 temporary support and flexible permanent sup­port with thick shotcrete and rock bolts are expected to be required. A low value of the strength/stress ratio may cause overbreak to occur in the disposal holes as well as in­creasing the costs of rock support.

The classification of the chemical composition of the groundwater (Table 3.3-6) with respect to pH, sulphate, carbon dioxide, ammonium and magnesium, is based on the classification of chemically aggressive environments, as described in the instructions for the preservation of concrete structures (Finnish Concrete Association 1992). Accord­ingly, non-aggressive and weakly aggressive environments were placed into the normal class of constructability. Moderately aggressive environments were classified as de­manding and strongly and very strongly aggressive environments as very demanding.

Table 3.3-5. Constructability classes on the basis of strength/stress ratio.

Stress state/Class I Normal Demanding Very demanding i

Stable ! I tunnels and shafts

crucsfcru > 10 I Probable spalling I tunnels and shafts crucsfcru = 5- 10 !

I

Moderate spalling I tunnels and shafts crucsfcru = 3 - 5 !

i

Rock burst !

crucsfcru < 3 I tunnels and shafts

38

Table 3.3-6. Constructability classes on the basis of groundwater chemistry.

Chemical composition I Normal Demanding Very demanding of ground water/Class I

--pH--··-·--·-··----··--·r---····-·-····-;·-s.5·····--·--···-·-····-· -··-······-·····--·s:-5---~----4~5··-···-·-···-········ ·-·····················-~--4-:5··-··-···-························

Sulphate (mg/1) I < 600 600 - 3000 > 3000 I

C02, free (mg/1) J < 30 30 - 60 > 60

Ammonium (mg/1) I < 30 30 - 60 > 60 -·--·-··-------·-·--··--·----··---·----r-··----···-·-··-··----··-·····--······-- ··-·····-·····-·--···-··--·-·--·-···--·-···-····-·-···· ····-·················--·-·······-··--·-·········--·········-····

Magnesium (mg/1) ! < 300 300 - 1500 > 1500

Chloride (mg/1) I < 1000 1000 - 4000 > 4000

Radon (Bq/1) I < 500 500 - 2000 > 2000

The classification of constructability with regard to the chloride content of the groundwater is based on the critical limit values that have been determined for concrete (Leinonen 1997). In this report the limit values are given in terms of the weight percent of concrete, but have been converted to equivalent values of mg/1 of chloride in ground­water, taking into account the differences in volumetric proportions of concrete and water, and by supposing that the differences in concentration of chloride in ground water and concrete become equal with time. The probability of chloride corrosion is assumed to be vanishingly small, when the chloride content corresponding to the normal class, as shown in Table 3.3-6, is considered. The probability of corrosion is assumed to be moderate when the chloride content lies in the demanding class and high when the chloride content lies in the very demanding class.

In the constructability classification the limit values for the radon content of ground­water were based on the following assumptions:

- in the normal class the radon content of tunnel air must not exceed a limit value of 400 Bq/m3

, which is based to the Radiation Act (59211991) in relation to normal work­ing practices

- in the demanding class the radon content of tunnel air varies in the range 400 - 1600 Bq/m3

, in which case underground working would be considered radiation work according to the Radiation Act. In such circumstances the employer would have to ensure that workers' radiation doses were monitored and that suitable medical checks were carried out, which would be more extensive than those associated with non-radiation work

- in the very demanding class the radon content exceeds 1600 Bq/m3, which would re­

quire the radon content to be reduced by active means, such as ventilation

- it is assumed that all the radon in the groundwater is released into the air in the tunnel according to equation 3.3-1 (Vesterbacka & Arvela 1998):

(3.3-1)

where

39

Gv = radon source strength from groundwater v = ground water ingress into a tunnel (m3 /day) Cv = radon content of ingressed ground water (Bq/m3

).

-the equilibrium content is determined using equation 3.3-2, in which the radon content of the ventilation air is assumed to be zero (Vesterbacka & Arvela 1998):

where

Ctp = Gv/V n+A.

Ctp = equilibrium content of radon in air (Bq/m3)

Gv = radon source strength from groundwater (Bq/h) V =volume of tunnel(= 1400 m3/100 m)) n = ventilation coefficient ( 1/h)

'A =decay constant of radon (0.00756 1/h)

(3.3-2)

-rate of froundwater ingress into tunnel is assumed to be 51/min/100 m tunnel (= 7.2 m per day)

- ventilation coefficient of tunnel is assumed to be 0.5 1/h

- no more than about half of the radon content used to determine the class limit may be released from the ground water, the other half is reserved for release from other sources (e.g. tunnel walls and floor).

The classification of rock engineering properties (Table 3.3-7) is mainly based on engi­neering judgement. The levels and types of drilling, blasting, crushing and rock support which commonly take place in underground construction projects in Finland, were classified as being normal from the constructability point of view. In the demanding class a significant reduction in the excavation rate (e.g. due to an increase in drilling times), or a reduction in the quality of the underground openings (e.g. due to problems with blasting and crushing) may occur, or more demanding constructional methods may also be needed (e.g. those requiring rock support). All these operations usually lead to increasing costs for construction and such increases can be considerable when dealing with the very demanding class of rock. Some examples of the increase in complexity when dealing with construction in demanding and very demanding classes are given in Table 3.3-7.

40

Table 3.3-7. Constructability classes on the basis of rock engineering properties.

Rock engineering Normal Demanding Very demanding property /Class

._. ..... _ _.. ...... -~ -~-··--·-· ........ --.. _____ ....,. ..... ________ , .... ....... ___ , _ __.....,._.. ..................... - .... _.,.._ ..................................

Drill ability easy or normal to hard to drill, e.g. very hard to drill, e.g. drill aphanite or very hard crushed rock (holes may

rock collapse and drills may jam)

Blasting properties easy or normal to hard to blast, e.g. very hard to blast, e.g. blast strongly foliated or dense 1 crushed rock

fracturing l

Crushing easy or normal to hard to crush, e.g. very hard to crush, e.g. properties crush (good to strongly foliated or tough weathered or crushed

moderate crushed rock (moderate to fair rock (poor crushed aggregate quality) crushed aggregate aggregate quality)

quality)

Rock support intact rock, no more hard to support, e.g. very hard to support, e.g. than normal support hydraulically-conductive crushed rock which needed rock or rock which needs needs heavy support

temporary support

41

3.4 Spatial distribution of the constructability in the bedrock

The spatial distribution of the constructability of the bedrock was examined separately for the classification parameters with respect to five variables: 1) rock type, 2) depth, 3) intact rock/R-structure (whether the rock mass in question is intact rock or lies within an R-structure of the bedrock model), 4) block number and 5) borehole number (Table 3.4-1). Of these, the rock type and depth were chosen because they were known to be significant for some classification parameters. Likewise, it was decided that the division of the bedrock into intact rock and R-structures, according to the bedrock model (Saksa et al. 1996), would be useful, as it was associated with the concept of good and poor rock. The R-structures were examined separately, using many of the classification parameters, to investigate their mutual differences. Block-specific and borehole-specific examinations of the constructability were carried out to study the regional distribution of the constructability.

The lithological properties were usually examined or estimated with reference to differ­ent rock types (Table 3.4-1). However, the degree of weathering was also examined with regard to variables 2 - 4.

The fracture properties were normally examined with respect to variables 1 - 4. The number of fracture sets was, however, examined only with respect to rock type and the frictional properties only with respect to variables 1 and 3.

The hydraulic conductivity of rock was examined with respect to variables 1 - 4. The rock's groutability and the groundwater ingress were examined with respect to variables 2 and 3.

The structural rock type (Table 3.2-2) of intact, fractured and crushed rock, was examined with respect to all variables, except the depth. The hydraulically-conductive rock was examined with respect to variables 2 and 3.

The in situ state of stress and groundwater chemistry were normally examined with respect to depth. The chloride content of groundwater was also examined with respect to borehole number.

Rock engineering properties were normally examined with respect to rock type, with the exception of rock support, which was in addition examined with respect to depth and the division of the bedrock into intact rock or an R-structure.

The Q value of the NGI classification system was examined with respect to all five variables (1 - 5). The examination of rock mass classification parameters with respect to the five spatial variables listed above is shown in Table 3.4-1.

42

Table 3.4-1. Examination of rock mass classification parameters with respect to the five spatial variables described in the text. liS= intact rock/R-structure, X= dependence examined, (X) = dependence estimated.

Parameter/Spatial variable Rock type Depth liS Block Hole ' Lithological properties: '

Mineral composition X I (

Degree of foliation X ~

Grain size X I i

Degree of weathering (X) (X) X l Strength and deformation x I properties 1

Thermal properties X I ,

X

-Fr~~-;;;e properlf~s: -··-·-··---··-·-·-·-·····-···--· ··---·--···--·--·······--·····-··- ····--·-·······-··-····-···-···· ................... _ .................. f .................................... T .................................. .

~::u: ~~!~:~::sets ~ X X ! X I i

Fracture trace length X (X) (X) (X) ! Frictional properties Fracture width Hydrogeological properties: Hydraulic conductivity Water ingress and grouting properties Structural rock type: Intact, fractured and crushed rock

X

X

X

X

X

X

(X)

X

X

X

X

X

i

I (X) ~

(X)

X

Hydraulically-conductive rock X X I !

X

·--·-··--·--·-···---------·--·-------·--.. -· ,.. ................... ----· .. -· .............. _ ..................... _ ........................... -·-·•·-....................................... _ ............. _ .............. .

State of stress: I I Principal stresses Strength/stress ratio

X

X

I ' i i

! I I I j j

Groundwater chemistry: I i

pH X I Sulphate content X l Free carbon dioxide X ! Ammonium content ~ I Magnesium content !

~:~:~~::=~~nt ~ I ' X ------------·--·-·-·------·-·---··-·------·-···· -----....... --·-····· .. ··--· ............... -............... - .. , ........................................ ; ................................... . Rock engineering properties: I !

i i Drillability X ! i Blasting properties X l I Crushing properties X I j

Requirement for rock support X X X i i NGI classification: Q value X X X X X

43

4 ROCK MASS CLASSIFICATION

4.1 Lithological properties

4.1.1 Mineral composition

The bedrock at Olkiluoto consists of mica gneiss, granite/pegmatite, tonalite, amphibo­lite/metadiabase, tonalite gneiss and mylonite. These rock types are heterogeneous and their mineral compositions can vary marked! y.

The average mineral compositions of the rock types and their standard deviations are presented in Table 4.1-1, based on thin section analysis of core samples (Lindberg & Paananen 1991, 1992, Gehor et al. 1996, 1997). Only a few thin sections of minor rock types were studied and, for this reason, data on tonalite gneiss were combined with those on tonalite as they are rock types with similar petrological and strength properties. Mylonite was not considered as a lithologically distinct rock type as it is sheared mica gneiss and a total length of only 3 m had been encountered in the boreholes. Ranges in the mineral composition of the rock types are shown in Table 4.1-2.

Table 4.1-1. The average mineral compositions of rock types and their standard deviations.

Rock type (number of thin Plagio- Quartz Potassium Micas Am phi-

sections )/Mineral ~om positi.~n i.~) _ ---~~-~~----------···-·-··--·-····--····!~!~~.e.~~--·-·---·--·-·················-···········-~~-~-~~---··-Mica gneiss (94) 29 (11) 31 (12) 8 (11) 25 (12) 1 (3)

Granite/pegmatite (11) 20 (10) 27 (8) 45 (14) 5 (4) 0 (0)

Tonalite (13) 38 (7) 23 (7) 10 (10) 24 (8) 3 (8)

Amphibolite/metadiabase (2) 22 (27) 7 (10) 0 (0) 25 (21) 42 (22)

Table 4.1-2. Ranges of mineral composition of the rock types.

Rock type (number of thin Plagio- Quartz Potassium Micas Amp hi-sections)/Mineral composition(%) clase feldspar boles

~-~~, ..........

Mica gneiss (94) 1 - 56 7- 66 0- 64 0- 68 0- 28

Granite/pegmatite (11) 7 - 41 11 - 46 18 - 63 0 - 13 -

Tonalite (13) 28- 48 7- 32 0- 22 6- 37 0 - 21

Amphibolite/metadiabase (2) 3 - 41 0- 14 - 10- 40 27- 58

44

The modal (volume) composition of migmatitic mica gneiss varies from quartz-rich granitoid to tonalite and granite. Amphibolitic and mica-rich sections are characteristic of this rock type and granitic veins have also been found. The degree of migmatization of mica gneiss varies considerably and the strongly migmatized mica gneiss in the southern part of the area is also referred to as veined gneiss (neosome > 50 o/o ). The mineral composition of mica gneiss varies, with a typical average of about 30 o/o plagio­clase, 30 % quartz, 25 % micas and 1 % amphiboles. In places a lot of pyrite is present, giving the rock a dotted and striped appearance. Cordierite and sillimanite are relatively abundant in places and chlorite and saussurite have been found locally.

From its modal composition granite/pegmatite is a granite. This rock type contains remnants of mica gneiss, mica rich stripes and amphibolitic sections in the core and its composition is typically about 20 % plagioclase, 25 % quartz, 45 % potassium feldspar and 5 % micas.

Tonalite varies from tonalite to granodiorite in its modal composition and its average composition is about 40 % plagioclase, 25 % quartz, 10 % potassium feldspar and 25 % micas. In places mica gneiss inclusions and amphibole rich sections in the core appear.

The variation in the composition of the amphibolite/metadiabase is difficult to estimate because of the small number of thin sections, but would appear to be about 20 % plagio­clase, 5 % quartz, 25 % micas and 40 % amphiboles.

Swelling clay minerals have been found occasionally in every borehole and at all depths associated with fractures and fracture zones (Lindberg & Paananen 1991, 1992, Gehor et al. 1996, 1997).

The main rock types at Olkiluoto consist of common rock-forming minerals. The pres­ence of amphiboles in amphibolite/metadiabase and amphibolitic sections of the core make these rocks harder to blast than the other rock types of Olkiluoto. With regard to their mineral composition all the rock types of Olkiluoto were placed into the normal class of constructability.

4.1.2 Degree of foliation

The degree of foliation has been determined on the basis of rock descriptions presented in the drilling reports for the boreholes at Olkiluoto (Suomen Malmi Oy 1989a, 1989b, 1989c, 1990a, 1990b, Rautio & With 1991, Jokinen 1994, Rautio 1995a, 1995b, 1995c, 1996a, 1996b, Lindberg & Paananen 1991, 1992, Gehor et al. 1996, 1997). It was not possible, however, to estimate the degree of foliation over the whole length of the core, because it was not always reported. An unambiguous estimation of the degree of folia­tion is absent from about 25 % of total length of the core.

Mica gneiss is moderately to strongly foliated (Table 4.1-3). About 20% of the core sample length is mainly strongly foliated. Considerable portions of mica gneiss that are strongly foliated have been found in borehole KR3 (over ranges of depth of 0- 150 m and 300 - 500 m) and in borehole KR6 (over its whole length).

45

Table 4.1-3. Typical variation of the degree of foliation in the rock types at Olkiluoto.

Rock type Degree of foliation

Mica gneiss moderate - strong

Granite/pegmatite none -weak

Tonalite weak - moderate

Amphibolite/metadiabase none - strong

Granite/pegmatite is typically non-foliated or weakly foliated and sections of core which are moderately - strongly foliated are present only occasionally. The degree of foliation exhibited by tonalite mainly varies from weak to moderate. Amphibo­lite/metadiabase has been encountered in only short lengths of borehole core, and the foliation over more than a half of this length was not documented. Where the degree of foliation has been determined it varies across the whole range.

The rock types at Olkiluoto were placed mainly in the normal class of constructability with regard to the degree of foliation. A considerable number of borehole sections in mica gneiss are strongly foliated and they were therefore placed in the demanding class. Strongly foliated sections have been found only occasionally in other rock types (data are sparse from amphibolite/metadiabase ).

4.1.3 Grain size

The grain size of the rock types was estimated on the basis of rock descriptions presented in research reports (Lindberg & Paananen 1991, 1992, Gehor et al. 1996, 1997). The typical grain size of the rock types is shown in Table 4.1-4.

The grain size of mica gneiss varies from fine-grained to coarse-grained. There is typi­cally more fine-grained material in the palaeosome and coarser material in the neosome. The granite/pegmatite is mainly coarse-grained and tonalite medium-grained. The grain size of amphibolite/metadiabase varies from fine-grained to medium-grained.

All the rock types at Olkiluoto were placed into the normal class of constructability with regard to their grain size.

Table 4.1-4. The grain size of rock types at Olkiluoto. The symbols refer to the relative abundance (ooo =majority, oo =about half and o =occasional).

Rock type/Grain size Very fine- Fine- Medium- Coarse-grained grained grained grained

(<< 1 mm) (< 1 mm) (1- 5 mm) (> 5 mm) Mica gneiss 0 00 0

Granite/pegmatite 0 000

Tonalite 000

Amphibolitelmetadiabase 00 00

46

4.1.4 Degree of weathering

The input data for analysing the degree of weathering was obtained from the digital archive of site investigation data (TUTKA). At the Olkiluoto site, data were available from ten boreholes, KR1 - KR10. The original data were divided into sections, each having a length of one metre. The total length of intact rock from borehole core con­tained within the defined blocks was 5108 m. In addition, there was 336 m of core asso­ciated with structures within the blocks (internal structures) and 420 m of borehole core belonging to structures bounding the blocks. Data are available from nine of the ten blocks. Block 3 was combined with block 2 (no data from block 3).

The spatial distribution of the input data is presented in Figure 4.1-1, where the sparse­ness of the data compared with the volume of rock within the blocks and the fact that some of the most weathered sections are included as part of the internal structures of the blocks, is evident. The intact rock is either unweathered or at most slightly weathered. The distribution of the degree of weathering in each block does not differ significantly from that determined for the whole investigation area (Table 4.1-5). The weathering classes are defined in Table 4.1-6.

There is no correlation between the degree of weathering and the depth nor any signifi­cant dependence between the degree of weathering and rock type. Table 4.1-7 lists the sections of the fractured zones having a degree of weathering of at least Rp 1-2.

The degree of weathering of the bedrock at Olkiluoto is almost exclusively either un­weathered or slightly weathered and the constructability is therefore classified as nor­mal. Narrow sections within structures R19 and R20 present the most significant anomalies. These sections are nearly completely weathered and are therefore classified as very demanding.

Table 4.1-5. The degree of weathering of the intact rock at Olkiluoto vs block, N = length of core sample.

Area! RpO Rp0-1 Rp1 Rp1-2 Rp2 Rp2-3 Rp3 N Weathering (%) (%) (%) (%) (%) (%) (%) (m) degree

··-------Whole area 76 21 3 0 0 0 0 5108 Block 1 100 0 0 0 0 0 0 57 Block 2 47 53 0 0 0 0 0 432 Block 4 76 17 7 0 0 0 0 1907 Block 5 68 32 0 0 0 0 0 1660 Block 6 97 0 3 0 0 0 0 231 Block 7 100 0 0 0 0 0 0 72 Block 8 97 1 2 0 0 0 0 508 Block 9 100 0 0 0 0 0 0 81 Block 10 100 0 0 0 0 0 0 160

FT/PJa/28.10.1999/0LrpENG.CV5

50

-1 00

-250

-400

z -550

-700

-850

-1000 6793300

X 6792100

6791800

Angle Above Horizon : 15 degrees Viewing Direction: 20 degrees Exaggeration: 1 Zoom : 1.2

47

3

2

0

1526300 1526600

1524800 15251 00

y

Figure 4.1-1. Distribution of the degree ofweathering at Olkiluoto, internal structures of the blocks are taken into account. Core sample length = 5444 m.

Table 4.1-6. Definition of the weathering classes.

Weathering degree Description of weathering degree '----·-·--·----··----··-----·----···-····----·····--··- -··-·---··----··-----·--·-----·-·--·--··-·-·······-···-···-----·-··-·-·-···--···-·-··--··-·-·······

Rp3 Completely weathered

Rp2-3 Almost completely weathered

Rp2 Strongly weathered

Rpl-2 Moderately weathered

Rpl Slightly weathered

Rp0-1 Hardly weathered

RpO Unweathered

48

Table 4.1-7. The most weathered structure sections at the Olkiluoto site. RX refers to bore hole intersections of unmodelled structures.

Weathering degree/Location !

Structure Bore- Depth range Block l hole I -----------------..-----·---·-- ·----·---·---~----···-----· .... ---~-·--~-----------------·····---·-···--·----·······-,_·-··-···-·-····""'""* ....... ..-................................................ Completely or almost R19 KR7 82-84 4 completely weathered (Rp2-3 or Rp3)

R20 KR7 227- 228 bounding structure

Strongly or fairly strongly RX KR5 482-483 6 weathered (Rpl-2 or Rp2)

R9 KR5 280- 283 bounding structure

R15 KR2 1040- 1041 10

R17 KR4 523- 524 5

R19 KR4 81- 84 4

R20 KR7 286- 289 bounding structure

R20 KR10 260- 261 bounding structure

R21 KR4 758- 763 bounding structure

4.1.5 Strength and deformation properties

The strength and deformation properties of the rock types of the Olkiluoto investigation site (Table 4.1-8) have been determined from six boreholes (KR 1 - KR5 and KR 1 0) over a depth range of 109- 809 m using loading tests (Matikainen & Simonen 1992, Kuula 1994, Johansson & Autio 1995, Tolppanen et al. 1995, Hakala & HeikkiHi 1997a, 1997b ). The majority of testing was carried out on the mica gneiss.

Mica gneiss was found to be a strongly heterogeneous material with regard to its strength. This heterogeneity is well described by the 95 % confidence limits of the standard deviation of the maximum strength, which are 76- 138 MPa. The results of loading tests demonstrate that mica gneiss loses a significant part of its strength (30- 60 %) immediately upon reaching its maximum strength and at the same time a clear fracture surface is created. On the basis of the test results the strength of mica gneiss is shown to depend on its mica content, the degree of foliation and the moisture content of the samples.

Triaxial tests over a range of confining pressures from 0.5- 15 MPa showed that the strength of mica gneiss increases as the function of the confining pressure (Figure 4.1-2), however, the effect is not very significant at small confining pressures. The strength of water-saturated samples is on average 10 - 30 % less than that of dry samples (Figure 4.1-2).

49

Table 4.1-8. Strength and deformation properties of the rock types at Olkiluoto. The values presented are arithmetical means, with standard deviations in brackets, N = number of samples. The sample diameter varied from 42 - 62 mm.

Rock type/ Property

Mica gneiss

Granite/ pegmatite

Tonalite

crucs·strength

cr cd·strength

Maximum I O'cd· O'er Tensile I Young's strength I strength strength ~ modulus I strength I

O'ucs , (MPa) (MP a) O't (MPa) i E (GPa)

l i

(MP a) ~ 109.2 ! 90.5 49.5 10.8 I 61.5

(27.9) I (24.5) (12.2) (2.9) I (8.3) I N=59 ! N=49 N=50 N=24 I N= 109 i

133.8 I

107.5 30.1 ! 69.6 i !

(18.5) I (23.7) (8.3) I (5.7) I I

N=5 ~ N=2 N=2 l N=5

109.5 i I 64.5

(7.8) i

I (1.7) ! N=4 ! l N=4 l

= uniaxial compressive strength, maximum strength

= stress level at which uncontrolled microfracturing begins in sample

= stress level at which the microfracturing begins in sample

Poisson's ratio

V

0.23

(0.05)

N= 109

0.30

(0.04)

N=5

0.28

(0.02)

N=4

cr ci-strength

Tensile strength O't = determined by Brasilian test (the direct tension test (N = 18) gave a value 7. 6 MP a for mica gneiss)

In addition to the laboratory testing, the Rock Tester field measurement device has been used to determine the uniaxial compressive strength ( crucs) and elastic properties (E, v) of core samples at intervals of 30 m. The compressive strength values determined with the Rock Tester are shown in Table 4.1-9. There is normally a large deviation in the results of these field measurements and they are less reliable than those from laboratory tests. The rock types of the testing samples were determined according to the bedrock model.

Table 4.1-9. The arithmetic mean of the compressive strength values of the rock types at Olkiluoto determined with the Rock Tester field measurement device.

Rock type/Strength Strength O'ucs Standard Number of

----·-·-------·---·--·---··-··--·-- ···-··---··-··J~~~)----···-·---····--~~.!~.~!!~~--~~~~2 .... -·--·-·-·-········~-~~-~!~.~---··-·····--····· Mica gneiss 145 42 345

Tonalite 153 30 38

Granite/pegmatite 160 39 101

Amphibolite/metadiabase 108 16 4

50

The combined strength results of laboratory testing and Rock Tester measurements are presented in Table 4.1-10 according to rock type. With regard to their strength proper­ties the rock types were mainly classified into the normal class of constructability, how­ever, mica gneiss and tonalite were placed partly into the demanding class because of their low strength.

200

180

160

140 Peak strength/wet -CG D. 120 ~ .c 100 ..... C)

Peak strength/dry ' GO-strength/wet

c: Q)

80 ""' ..... en

60

40

20

0 -15 -10 -5 0 5 10 15 20

Confining pressure (MPa)

Figure 4.1-2. Compressive strength of the mica gneiss as a function of moisture and confining pressure.

Table 4.1-10 The combined strength results of laboratory testing and Rock Tester measurements.

Rock type/Strength Compressive strength O"ucs (MPa)

Mica gneiss 80- 140

Tonalite 80- 110

Granite/pegmatite 115 - 150

Amphibolite/metadiabase 100

51

4.1.6 Thermal properties

The thermal properties of rock samples (Table 4.1-11) taken from four bore holes (KR 1, KR2, KR3 and KR5, over a depth range of 107- 503 m) have been studied in the laboratory (Kj~rholt 1992, Kukkonen & Lindberg 1995, 1998).

The average temperature based on open borehole groundwater logging data from bore­holes KR1-KR5 at 500 m depth was 11.8 oc (Paulamald & Paananen 1995, Paananen & Paulamaki 1995). According to more recent borehole groundwater temperature logging from extended boreholes KR2 and KR4, the temperature is about 6- 6.5 oc at shallow depths and about 12.2- 12.7 oc at 500 m (Julkunen et al. 1995). The average tempera­ture gradient, which was calculated using linear regression over the whole depth range below a depth of 125 m was 1.4- 1.5°C/100 m and was considered to include the inter­ference caused by the drilling (Paulamaki & Paananen 1995, Paananen & Paulamaki 1995). The temperature gradient over the whole depth range lies in the range of 1.2- 1.6 °C/100 m in different boreholes, but locally over shorter intervals in boreholes KR2 and KR4 even lower gradients of 0.7- 0.9°C!l00 m are found at 500 m depth (Okko et al. 1990a, 1990b, Julkunen et al. 1995).

The thermal conductivities of the rock types have been calculated on the basis of their average mineral compositions (Table 4.1-1) and the thermal conductivity of minerals. In cases where the density and specific heat capacity of minerals were known the thermal diffusivities of the rock types have also been determined and are presented in Table 4.1-12, where the arithmethic and harmonic means are provided to represent the maxi­mum and minimum values respectively. The calculated harmonic means of the thermal conductivities correspond reasonably well with the measured values.

Table 4.1-11. The measured thermal properties of the rock types of Olkiluoto. The results are averages, standard deviation is given in brackets, N = number of samples.

Rock type/Parameter Thermal Heat Diffusivity Coefficient of conductivity capacity (lE-6 m2/s) thermal

(W/mK) (JikgK) expansion (1E-6/°C)

Temperature range 20 oc 60-99 oc 20 oc 10- 60 oc Mica gneiss 2.7 822 1.17 1.251) 9.5

(0.4) (30.9) (-) (0.17) (2.4)

N=6 N=8 N=1 N=5 N=3 •• ___ .__..,.,._., • ._ ______ u __ •• .. ._.._.""" .. ,._ .... ~ ........ ~----..-......... _._..~-...···· ·-·-~-···-··--~·-··~---······~-·--·- .............. ~--·-·····-· .............................................. ................................................................................

Granitelpegmatite 4.2 778 1.18 2.01)

(0.5) (6.0) (0.06) (0.20)

N=2 N=2 N=2 N=2

Tonalite 2.7 797 1.23

(0.1) (3.5) (0.06)

N=2 N=2 N=2

1) Calculated value

52

Table 4.1-12. The thermal conductivity (arithmetic and harmonic mean) and diffusivity of the rock types at Olkiluoto calculated on the basis of their average mineral composi­tions.

Rock type/Parameter Thermal conductivity (W /mK) Thermal diffusivity Arit. Harm. (lE-6 m2/s)

··-Mica gneiss 3.7 2.9 1.48

Tonalite 3.5 2.5 1.23 Granite/pegmatite 3.7 2.8 1.42

Amphibolite/metadiabase 2.8 2.5 1.27

The thermal properties of the rock types depend on the temperature. The calculated val­ues of thermal conductivity and thermal diffusivity have been calculated at room tem­perature. The thermal conductivity decreases by about 0.4 W/mK (about 10- 15% of the typical thermal conductivity of crystalline rock) over the temperature range from 20 to 100 °C, the corresponding increase in heat capacity being about 10 - 20 % over a similar temperature range.

On the basis of their thermal conductivities all the rock types of Olkiluoto were placed into the normal class of constructability.

53

4.2 Fracture properties

4.2.1 Fracture directions

The orientations of fractures at the Olkiluoto site have been mapped from outcrops and investigation trenches. The following fracture sets can be seen in these data (Figure 4.2-1, all observations): one of the two most prominent fracture sets is parallel to the foliation (070- 090°) with the other one being perpendicular to it (160- 190°). The third set, which is less well developed, intersects these at an oblique angle (orientation 020 - 040°) and is parallel to the foliation in the southeastern part of the site (Paulamaki et al. 1996). No major differences can be found in fracture orientations between the rock types (Figure 4.2-1 ). Mapping fractures on outcrops and in investigation trenches

Mica gneiss/veined gneiss (N = 1791)

Grani te/pe gmati te (N = 457)

Tonalite/tonalite gneiss (N = 689)

N

All observations (investigation trenches and outcrops) (N = 2945)

Figure 4.2-1. Distribution of the fracture directions of the main rock types at Olkiluoto, observed from surface mapping (Paulamiiki et al. 1996). Each ring in the rose diagrams represents 5 % of the distribution, N = number of observations.

54

favours those with steep dips. Measurements in boreholes show that a prominent sub­horizontal fracture set is present in every rock type. The strike of this subhorizontal fracturing is parallel to the foliation (Paulamaki et al. 1996) and it probably represents the same fracture set which was mapped in outcrops parallel to the foliation. The wide range in the dip of this fracture set can be explained by the folding of the bedrock.

In all of the main rock types there are two or three steeply dipping fracture sets and one gently dipping fracture set. At the tunnel scale it was assumed that there would be three fracture sets, and the bedrock was placed into the normal class of constructability based on this factor.

4.2.2 Fracture frequency

The input data for analysing the fracture frequency was gathered from the digital ar­chive of site investigation data (TUTKA). At Olkiluoto data were available from ten boreholes, KR1 - KR10 and two investigation trenches, TK1 - TK2. The original data were divided to sections of 1 m in length. The total length of intact rock in boreholes or trenches belonging to the blocks was 5782 m. In addition, there was 336 m of core associated with the structures within the blocks (internal structures) and 420 m of core associated with the structures bounding the blocks. Fracture frequency is presented as the number of fractures per metre. Part of the original data on fracture frequencies from core drilling was replaced with fracture frequencies calculated from the fracture data­base. This was considered more reliable as it combined the results of several investiga­tion methods.

The spatial distribution of the data belonging to the blocks is presented in Figure 4.2-2. The highest fracture frequencies (~ 15 fractures/m) occur in the internal structures (the bounding structures are not included in the analysis, but in some of them densely fractured sections also occur). The fracture frequencies presented are based directly on the results of core drilling. The orientation of fracturing was not taken into account in determining fracture frequency.

The distribution of fracture frequency in the intact rock is presented in Figure 4.2-3. The fracture frequencies of different blocks do not differ significantly from each other (Ta­ble 4.2-1 ). In general, the blocks are only slightly fractured, however densely fractured one metre sections occur occasionally. The only densely fractured zone in the intact rock is observed in borehole KR6 close to the surface over the depth range of 5 - 12 m.

To analyse the depth dependence of the fracture frequency the data were divided into four depth categories (Table 4.2-2). The frequency distributions of the different depth intervals were very similar to each other. The relation between the fracture frequency and the rock type was also studied (Table 4.2-2). No significant differences were ob­served between the rock types, although, tonalite seems to be less fractured than the other rock types.

FT/PJa/29.1 0.1999/0LrkiENG.CVS

50

-100

-250

-400

z -550

-700

-850

679~ 6793000

6792700

X

Angle Above Horizon: 15 degrees Viewing Direction : 20 degrees Exaggeration: 1 Zoom: 1.2

1524800

55

1525100

y

20

18

16

14

12

10

8

6

4

2

0

fractures/m

1526600

F=-t L-=.J

Figure 4.2-2. Spatial distribution of the fracture frequency at Olkiluoto, the internal structures are included (number of fractures/m, sample length= 6118 m).

Table 4.2-1. Distribution of fracture frequency in the intact rock vs block (N =observed length).

Area/ Sparsely Slightly Abundantly Densely N Fracture fractured fractured fractured fractured (m) frequency (< 1 (1- 3 (3 -10 (> 10 (%) fractures/m) fractures/m) fractures/m) fractures/m)

Whole area 33 51 16 0 5782 Block 1 37 51 12 0 57 Block 2 38 48 14 0 432 Block 4 30 54 16 0 2581 Block 5 31 51 17 1 1660 Block 6 48 40 12 0 231

Block 7 15 56 28 1 72

Block 8 37 41 21 1 508

Block 9 17 66 17 0 81 Block 10 41 44 14 1 160

56

35 32.5

30

25 24.6

~ c 20 = ClJ

= 15.6 C' ClJ

15 '"' ~ 10.5

10

6.2

5 4.0

0.2 0.1 0.0 0.0 0.0 0

0 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Number of fractures I m

Figure 4.2-3. Distribution of fracture frequency in the intact rock at Olkiluoto (observed length= 5782 m).

Table 4.2-2. Distribution of fracture frequency in the intact rock as a function of depth and rock type (N =observed length).

Depth range Sparsely Slightly Abundantly Densely N and rock type fractured fractured fractured fractured (m) /Fracture (< 1 (1- 3 (> 3- 10 (> 10 density(%) fractures/m) fractures/m) fractures/m) fractures/m)

Depth range 0- 200 m 28 54 17 0 2469 200-400 m 36 49 15 0 1346 400-600 m 33 50 16 1 992

>600m 39 44 16 1 975 ·-·---------·-- ••--•-·-------·-•-·•--••.....,._.._._,_.___.._.._,__..~•n• ..... •_....~.....-ooon~~.,., .... ,.__,...,, __ ,,,,.,,,,....,.,.,,, • .,.,_,~-•no-.oooooo.,...,.,,...,..,.,._._, ............ ,_ .. ,,,, .. ,, .... ,,._._,...,,.,,,,..,,,,,,,._, • ..,.,,._u0000000u-.oooououoouo

Rock type Mica gneiss 31 51 17 1 4381 Granite/ pegmatite

33 52 15 0 917

Tonalite 51 40 9 0 444 Amphibolite/ metadiabase

25 53 22 0 36

57

The fracture frequency of the R-structures was analysed on the basis of the RQD index (Table 4.2-3). The proportions and the mean borehole intersection lengths belonging to three fracture frequency categories were calculated for each structure. A densely frac­tured section was considered to be significant (from a tunnelling point of view) if its mean length were greater than 3 m (the approximate length of one tunnelling round in densely fractured bedrock). The calculation method does not take notice how the densely fractured rock is distributed within a single borehole intersection of an R­structure or between different borehole intersections of the same R-structure.

The intact rock was placed into the normal class of constructability based on its fracture frequency, which was found not to depend on the rock type, the depth or the block from where the data were derived. Most of the R -structures were placed into the normal class of constructability, however, structures R9, R17 and R21 contain significant sections considered as demanding. Some sections of structures R12 and R24 were classified as very demanding.

Table 4.2-3. The fracture frequency distributions for R -structures at Olkiluoto based on the RQD index (in parentheses the average length of intersection in metres). RX = unmodelled structure, L = length along bore hole axis, N = number of intersections.

Structure/ Fracture frequency

RX R1 R2 R9 R10 R11 R12 R13 R14 R15 R17 R19 R20 R21 R24 R26 R30

RQD51-100% (0 -17

fractures/m)

95 (7)

84 (3) 94 (17)

67 (8)

97 (19)

83 (5)

60 (6)

80 (8)

50 (1)

0 (0)

80 (12)

91 (3)

83 (14)

83 (15)

87 (17)

93 (3)

100 (5)

RQD 26 · 50 % I RQD 0 • 25 o/o c11 • 21 1 c> 21

fractures/m) ! fractures/m)

4 (0) 1 (0)

8 (0)

6 (1)

25 (3)

3 (1)

17 (1)

20 (2)

20 (2)

50 (1)

100 (2)

18

9

14 9

5

7

0

(3)

(0)

(2)

(2)

(1)

(0)

(0)

8 (0)

0 (0)

8 (0) 0 (0)

0 (0)

20 (2)

0 (0)

0 (0)

0 (0)

2 (0)

0 (0)

3 (0)

8 (1)

8 (2) 0 (0)

0 (0) I

L (m)

148 12

18 24 60

6

10

10

2

2

45

11

66 70

39

14 5

N (inter­

sections)

19

3

1

2

3

1

1

1

1

1

3

3

4

4

2

4

1

58

4.2.3 Trace length

Input data for the trace length analysis of fractures are derived from the surface mapping of outcrops (Paulamill.d 1989), from the investigation trenches TK1 ( 406 m) and TK2 (405 m) (Paulamaki 1995, 1996) and from the borehole radar measurements (Carlsten 1996a, 1996b, Saksa et al. 1997). The data obtained from surface mapping and those derived from borehole investigations are not combined.

In surface mapping the accuracy of the trace lengths of fractures having a length > 1 m is 0.5 m. The fractures that were visible over their entire length were distinguished from those that are truncated, and the true trace lengths of the truncated fractures are un­known (Paulamaki 1989). Surface observations were available for blocks 2 and 4. The observations within the internal structures of the blocks were combined with the data for the intact rock of the block, as there were insufficient data to analyse them separately. Only investigation trenches, both of them located in the block 4, provided information on the trace lengths of fractures within structures.

Table 4.2-4 presents the distribution of fracture trace lengths in the blocks and in the different rock types. The trace lengths are known for 35-47% of the fractures. The average length of the completely visible fractures is slightly less than the average of the total. The longest fractures are not well represented, as the size and width of the out­crops and investigation trenches limit the observed lengths.

Block 2 and tonalite have a greater proportion of fractures having lengths above 5 m, because most of the observations are from the wide tonalite outcrop of Selkanummen­harju. At this outcrop, 12 - 15 % of the fractures are longer than 5 m and the mean trace length of all the fractures and fractures with known trace lengths is 3.2 m. The fracture frequency does not differ from other observations on the site (Paulamaki 1989), so it can be concluded that the proportion of long fractures can be based on these results. Other rock types or subareas do not differ from the general trend. The distributions of trace lengths shown in Table 4.2-4 are consistent with the previously reported results from surface mapping of the whole site (Paulamill.d 1989, 1995, 1996).

In general, surface mapping provides better estimates of the intact rock than of the fractured zones (despite the presence of the investigation trenches). Steeply dipping fractures are also likely to be observed more frequently during surface mapping than those fractures with more gentle dips.

59

Table 4.2-4. The fracture trace length distribution in the outcrops and the investigation trenches (N = number of observed fractures).

Input data/ 11 Total Percentage (%) Length Length j Percentage (%)

Variable . known o/o known ! f------l---,......-----.-·--+--·---1------·---i---............... ---·-· ·--·-----1 Average Below I 3 - 5 I Above Average j Below I 3 - 51 Above 1 length (m) 3 m j m I 5 m length (m) I 3 m I m 5 m

Mica j 2.0 80 1 17 I 3 36 1.6 I 91 7 j 1

gneiss 1

1

1 ·.:! (N = 365) 1

(N = 1018) I I 64

11 26 1 10

I! !

46 (N = 193)

2.3 I

76 I 18 6 I ~ ! i

Tonalite 11

:

(N = 424) 2.7

The true trace lengths of the fractures observed in the boreholes are unknown. Borehole radar results only provide estimates of the trace length of the longest fractures. The trace length of a reflector based on radar measurements (60 MHz, Carlsten 1996a, 1996b) is calculated from its observed length along the borehole and the angle between the reflector and the borehole (Saksa et al. 1997). Trace lengths of fractures intersected by boreholes were obtained from the fracture database (for boreholes KRl, KR2, KR4 and KRlO) or were calculated specifically for this purpose (boreholes KR3, KR6, KR7 and KR8). In boreholes KR5 and KR9 no radar measurements were carried out. In deep boreholes KR2 - KR4 the measurements commenced at depths of 60 - 90 m, since at shallower depths attenuation of the radar signal was too strong because of the high electrical conductivity of the bedrock.

The radar reflectors are associated with local fracture zones, with single, distinguishable long fractures, or with parts of the major fracture zones. At Olkiluoto the reflections could also possibly be due to the presence of layers containing electrically conductive minerals (graphite, pyrite, etc.) that are often parallel to the foliation. Fractures filled with these conductive minerals are also occasionally observed. The prerequisites for the detectability of a reflector are a sufficient width and a sufficiently great electrical contrast with the surrounding rock. In contrast, several local fracture zones with no associated radar reflectors are also present. This lack of reflectors can be due to an unfavourable intersection angle of a gently dipping structure with the detection system or to the attenuation of the radar signal due to saline groundwater. The radar results do not provide information on the origin of the reflector (unless such information is available from an external source). All radar reflectors are considered to represent fractures, and are used to analyse the fracture trace lengths.

60

The trace length of a reflector depends on the fracture length, as well as the penetration of the radar (at Olkiluoto the penetration is 10- 25 m at a frequency of 60 MHz). The intersection angle of the reflective plane and the borehole axis and the structural properties (such as electric conductivity, width) also affect the trace length. Reflectors parallel to the borehole have the longest trace lengths, whereas reflectors intersecting the borehole with an angle > 60- 70° are undetectable. This orientation effect is, how­ever, not considered here. The location of the borehole/reflector intersection determines the block to which the reflector is assigned, although the fracture can extend to several blocks. In cases where the reflector did not intersect the borehole itself but its assumed continuation, the reflector was assigned to the block in which the trace was observed.

The distribution of reflector trace length was studied with respect to the block, the rock type, the depth, the internal structures of the rock and within the intact rock. Including their internal structures, there are 337 radar reflectors within the blocks. Blocks 4 and 5 have the greatest number of reflectors. Radar reflectors are observed at 12 m intervals on average in the intact rock and at 6 -12 m intervals in the R-structures. Compared with the fracture frequency of the intact rock, about 2 - 8 % of all fractures are detected in radar measurements and reflector trace lengths are significantly greater than the average fracture trace length measured on the surface. Radar reflectors are thus expected to be associated only with the longest fractures and minor local fracture zones that represent a small portion of the total number of fractures. Long trace lengths only occur sparsely in outcrops, and are therefore in agreement with the radar observations. It can be reasona­bly assumed that this sparseness is representative of conditions at depth and that the constructability of the rock mass would not be unduly affected by this factor except in major fracture zones.

Over 25 % of the reflector trace lengths are < 10 m, with most of the reflectors ( 44 %) having lengths of 10 - 20 m, and 60 % of the reflector trace lengths of between 10- 30 m. The mean trace length of the 327 reflectors intersecting the boreholes with intersection angles > 10° is 18 m, with the trace lengths lying in the range 0.1 - 94 m (calculated trace lengths approach 0 m when the intersection angle is 90°, because reflections originate from the same point irrespective of the distance from the reflecting plane). The reflector trace length distribution is similar both in the intact rock and in the R-structures. Within the internal structures of blocks (7 % of the core sample length) the reflector trace lengths are nearly the same as those in the intact rock. The differences between the blocks are only minor, both in the intact rock and in the structures, and no specific conclusions can be drawn. In the internal structures (representing 0 - 10 % of the borehole length in each block) and in the intact rock the variation between the blocks is only slight.

The mean reflector trace length varies between 13 - 19 m, if trace lengths over 50 m are excluded. The longest traces occur within the depth interval of 100 - 300 m, where the bedrock is intact, and the salinity of the ground water is low.

Most of the reflectors are from mica gneiss (77 %) and granite/pegmatite (20 % ). The detected reflectors are distributed in similar proportions by rock type, making the sam­ple set representative. Most of the reflector observations in the structures are from mica

61

gneiss. The mean trace lengths in different rock types vary between 16 - 20 m, if only lengths below 50 m are included, and no noticeable differences between rock types are apparent.

Based on the distribution of trace lengths the bedrock of the Olkiluoto site was placed into the normal class of constructability. Locally, single long fractures can occur both in the intact rock and in the R-structures, but fractures with extensive trace lengths are sparse.

4.2.4 Frictional properties

The frictional properties of the fractures were examined using the joint alteration num­ber CJa) and joint roughness number CJr) of the NGI classification system and the JrfJa ratio. Function <1> = arctan(Jr11a) gives an approximation to the friction angle of a fracture (Barton et al. 1974). Data for these calculations were obtained from boreholes KR1 -KR 10. Fracture surface roughnesses were determined and the most critical fracture (with the lowest Jr!Ja ratio) was chosen to represent the value of each metre of core. The examination of the frictional properties of the fractures was made separate! y for intact rock and R-structures. The definition of friction parameters is described in more detail in Section 4.8.

The frictional properties CJr, Ja and<!>) of the R-structures were examined on a structure by structure basis (Table 4.2-5 and Appendix 1). Where a structure was intersected by more than one borehole an average value was calculated based on the values from each borehole. Structures that had at least 3 m (approximately the length of one tunnelling round in heavily fractured rock) of core length classified as demanding or very de­manding were estimated to be the most significant ones with respect to frictional prop­erties. This procedure does not take into account how the frictional properties are dis­tributed over the complete intersection length of the R-structure in a borehole or how they might be distributed between the different boreholes intersecting the same R­structure.

The relative proportions of fractures with different roughness and alteration properties do not vary significantly as a function of depth. Clay minerals, including swelling clay, have been found occasionally in every borehole at all depths associated with fractures (Lindberg & Paananen 1991, 1992, Gehor et al. 1996, 1997). The distribution of the frictional parameters Jr, la and <I> is presented in Figures 4.2-4- 4.2-6.

In intact rock the fractures are typically irregular or curved/rough or semi-rough (large­scale/small-scale roughness), in which case 1r = 3 (Figure 4.2-4). Fracture properties that correspond to the values of 1r and Ja are shown in Tables 4.8-2 and 4.8-3. Pla­nar/rough or semi-rough and irregular/slickensided fractures CJr = 1.5) have been ob­served in 10- 20% of the fractures.

62

Table 4.2-5. Distribution of frictional properties in the most significant structures with regard to the fracture properties, which are given as average length per one borehole intersection (of a structure) and as a percentage (in brackets). Complete table is pre­sented in Appendix 1.

Structure/ I Jr = 1 lr = 0.5 Frictional

I de m very dem

property (m(%)) I

!

R2 I R9 ! RlO 13.3 (8.3) 1.7 (8.3)

R12 p.o (IO.Q) 2.0 (20.0) I

R13 !2.0 (20.0) 5.0 (50.0) I

R17 !2.3 (15.6) 0.7 (4.4) !

R20 12.5 (15.2) 1.0 (6.1) !

R21 16.8 (38.6) 1.3 (7.1)

R24 !t.5 (7.7) 3.5 (17.9)

de m = demanding class very dem = very demanding class

Mica gneiss ( 4020 m)

100

80

% 60

40

20

0

0.5 1.5 2

lr

Tonalite (370 m)

100

80

% 60

40

20 0.3 1.4

0

0.5 1.5 2

lr

la =4 Ja =8 de m de m

5.0 (27.8)

6.5 (54.2)

5.0 (50.0)

3.0 (30.0)

4.0 (26.7) 1.0 (6.7)

2.8 (16.7) 1.8 (1 0.6)

0.5 (2.9) 2.5 (14.3)

100

66.3 80

% 60

40

20

0

3

100 81.9

80

% 60

40

20

0

3

la= 10 <1> = 0. 7 <1> = 7 -15 very dem very dem de m

7.0 (70.0)

3.5 (20.0)

4.0 (20.5)

Granite/pegmatite (896 m)

0.5 1.5 2 3

Jr

Amphibolite/metadiabase ( 41 m)

0.0

0.5 1.5

lr

2 3

Figure 4.2-4. Distribution of joint roughness number ( lr) in rock types without structures. Total length of core sample is given in brackets.

63

The joint alteration number Ja usually has a value of 0.75 or 2 in intact rock at Olkiluoto (Figure 4.2-5), in which case the rock is unfractured (or fracture surfaces coalescence), there is no fracture filling, or the filling has not been specified in the drilling reports, or the filling is tight, hard and impermeable. Thin fracture fillings which are softening or have low friction (J a = 4) occur in about 5 - 10 % of the core length (at least one such fracture per metre of core). Crushed rock and/or fractures including thick (> 2 mm) clay mineral fillings have been observed only occasionally(=:::; 0.2% of the core length).

Typical friction angles are > 30° in intact rock (Figure 4.2-6), with the highest values usually being associated with unfractured borehole sections. At Olkiluoto about 35 % of the friction angles in mica gneiss, granite/pegmatite and amphibolite/pegmatite and > 60% of those in tonalite can be explained in this way. In mica gneiss and amphibo­lite/metadiabase about 5% of fractures have low friction angles (7- 15°). Very low friction angles(=:::; 7°) have not been observed.

Figure 4.2-5. Distribution of joint alteration number (la) in different rock types without structures. Total length of core sample is given in brackets.

64

Mica gneiss ( 4020 m) Granitelpegmatite (896 m)

70 70

60 60

50 41,8 50 45,8

40 40 % 30 22,9 22,6 % 30 24,8

21,0

20 20

10 0,0 10 0,0 1,1

0 0-r-- 1/j 0 1/j 0 0 r-- ~ 0 1/j 0 0

0 - ('f) "'1 \.0 ":' 0 ('f) "'1 \.0 ":' I

~ ..0 r!- ~ ..0 r-- - \0 -('f)

""'" ('f)

""'" \.0

Friction angle ( <!>) Friction angle(<)>)

Tonalite (370 m) Amphibolite/metadiabase (41 m)

70 67,0

70

60 60

50 50 39,0 36,6 40 40

% 30 % 30 19,5 20 20

10 0,0 0,5 10 0,0

0 0 r-- ~ 0 1/j 0 0 r-- 1/j 0 1/j 0 0

0 ('f) :! \.0 ":' 0 ('f) "'1 \.0 ":' I

~ ..0 r!- ~ ..0 r-- \0 \0 ('f)

""'" ('f)

""'" Friction angle(<)>) Friction angle(<)>)

Figure 4.2-6. Friction angle of rock types in intact rock. Total length of core sample is given in brackets.

The R-structures of Olkiluoto often have Jr values 1.5 or 3 (Appendix 1), i.e. they are planar/rough to semi-rough, irregular/slickensided or irregular/rough to semi-rough. Planar/smooth or slickensided fractures or fractures with no rock-wall contact (Jr = 0.5 or 1) have been found to a significant extent (i.e. covering on average at least 3 m of core within a borehole intersection of a structure) in structures R10, R12, R13, R17, R20, R21 and R24 (Table 4.2-5). The fractures belonging to the R-structures are usually filled but the filling has not been identified in the drilling reports or the fillings consist of non-softening minerals (Ja = 2). Thin, softening fracture fillings with a low friction angle have been identified in the structures R2, R9, R12, R13, R17, R20 and R21 (Ja = 4). In the structures R17, R20 and R21 there are also sections of crushed rock and/or fractures with over 2 mm of clay mineral filling (Ja = 8).

Most of the friction angles in the R-structures lie in the range 31 - 45° and high friction angles are rare. Low friction angles (7 - 15°) have been observed significantly in struc­tures R 13, R21 and R24 and very low friction angles have not been found at all.

The frictional properties of the intact rock of Olkiluoto place it in the normal class of constructability. 1 - 7% of rock was classified as demanding and < 3% as very de­manding with respect to the joint roughness number. 3 - 10 % of the intact rock was placed in the demanding class with respect to the joint alteration number. About 5% of

65

the mica gneiss and amphibolite/metadiabase and about 1 % of the granite/pegmatite and tonalite were classified as demanding with respect to the friction angle.

The frictional properties of the structures R1, R11, R14, R15, R19, R26 and R30, as well as the unmodelled structure intersections (RX), place them in the normal class of constructability. The structures R2, R9, RIO, Rl2, R13, R17, R20, R21 and R24 were classified in part as demanding and the structures R 12, R 13 and R24 in part as very de­manding.

4.2.5 Fracture width

The analysis of fracture widths is based on the interpretations of the high resolution op­tical borehole-TV imaging measurements (Stdihle 1996), bore hole core (Suomen Malmi Oy 1989a, 1989b, 1990a, Rautio 1995b, 1995c, 1996a), and the fracture database, which combines all fracture data from geological mapping with corresponding data from bore­hole-TV images, dipmeter and acoustic televiewer logging (Saksa et al. 1997).

The term fracture width refers to the sum of the mineral filling thickness and the frac­ture aperture. Where the interpretation is available (Stn'lhle 1996) the fracture width is determined from the interpretations of fractures visible in borehole-TV images. The minimum apparent width (measured along the borehole axis, being uncorrected with respect to the borehole intersection angle) obtained using this method is 1 mm, which is the measurement resolution applied. It is not possible on the basis of the TV image to determine the proportion of the fracture which is infilled, or come to any definite conclusions regarding the mechanical quality of the filling (softness, etc.), although some indirect indication of mechanical quality sometimes be obtained from the filling minerals visible on the trace. The values of the fracture widths assumed are either the apparent width along the borehole axis (when using the original results from borehole­TV image logging, where the widths were not corrected for fracture orientation) or the true corrected width along the normal of the fracture plane (derived from the TV image data for the fracture database, Saksa et al. 1997). Both the apparent and true widths are treated equally, combining data from the sections of the boreholes which are included within the fracture database with those which are not. The bias caused by this procedure was considered to be of minor importance.

In portions of the boreholes covered by the fracture database (Saksa et al. 1997) all frac­tures were used in the analysis, not only those detected by borehole-TV. Outside the range of the fracture database only fractures detected by borehole-TV were used since only these include information on width. To complicate the situation, borehole-TV data are missing from some sections included in the fracture database. The number of frac­tures is considerably greater in the borehole sections where the fracture database is available than in the sections where data are only available from borehole-TV data alone. Due to this bias, the distribution of fractures classified as being "open" were not used in this study as a parameter. Only fractures with a measurable width were studied, and then only for determining the distribution of fracture widths, not for analysing their "type". The input data used in the analysis of fracture widths are presented in Table 4.2-6.

66

The results of core drilling and fracture mineral studies contain descriptions of fracture types and occasionally the thickness of the mineral filling, but not the aperture, so the borehole intervals studied only by core logging were excluded from the analysis. For the fracture database the fracture data have been edited to a uniform form, and are used in this analysis even when the interpretation of the borehole-TV is unavailable. The pro­portion of large fracture widths in these sections is likely to have been underestimated because of the possibility of core loss or the presence of fractures with large apertures (Table 4.2-6).

Fracture widths were studied using data on the borehole intervals within the blocks. There are 4634 observed fractures in these intervals and the fracture type and width is known for 1694 (37 %) of these. 1263 of these fractures are open, filled or weathered and 431 are tight and fractures with a reported width of 0 mm or those with unmeas­urable widths are excluded from the analysis. These excluded fractures can be filled, weathered and open (1776, 38% ), tight or fractures of unknown type (1159, 25 % ). The width of tight fractures is, in practice, less than 1 mm or is not reported. Table 4.2-7 presents the main observations on fracture widths with respect to the complete database, three depth intervals, the intact rock and the R-structures as well as in relation to the main rock types.

Most of the fracture widths are less than 5 mm. The mean value would be significantly less if the width of the tight fractures could be measured and included in the analysis. The fractures having a width over 5 mm form 8 % of the fractures with known width (or 1.8% of all the observed fractures). Only 23 fractures having width over 20 mm are observed (1.4% of the fractures with reported widths). The largest fracture widths ob­served occur in the internal structures of the blocks, where the fractures or the densely fractured sections are weathered or contain fine-grained filling material. The greatest widths observed are 121 mm in bore hole KR4 in structure R 19 at the depth of 82 m, 116 mm in borehole KR1 in structure R10 at the depth of 525 m and 87 mm in borehole KR4 in structure R17 at the depth of 510 m.

Table 4.2-6. Input data for analysis of fracture width at Olkiluoto.

Data Boreholes (depth intervals)

Fracture database (Saksa et al. 1997) KR1 (300- 9002)), KR2 (300- 8802

)), KR4 (300- 9002)),

KR10 (250- 6141))

Interpretation of borehole-TV KR1 (40- 300, 944- 984), KR2 (200- 300), measurements (Strahle 1996) KR4 (40- 180, 280- 300)

Core drilling and fracture mineral KR1 (900- 944), KR3, KR5, KR6, KR7, KR8, KR9 studies (no information of width)

1) KR10, borehole-TV measurements are not included in the fracture database, so no width information is available (in borehole KR10 televiewer measurements containing no information on width were carried out)

2) Interpretation ofborehole-TV measurements are not available for the following depth intervals: KR1 341-500 m and 644 -740 m, KR2 300- 390 m and 440-539 m as well as KR4 390- 480 m and 570-739 m

67

Table 4.2-7. The mean of fracture width and the proportion of fractures with a width above 5 mm calculated on the basis of the data presented in Table 4.2-6.

I Mean fracture Fracture width I width (range) > 5 mm I (mm) (o/o)

Data (number offractures)/Fracture width

··-----------·----·- .--------·-----···-·-·-----·-r-··-··-·--··----·····----···-······-·--······-··-·····-····--··-··-·-··· Total Total (1694) 1 2.6 (0.1 - 121) 8

Intact rock (1406) I 2.1 (0.1 - 79) 6

R-structures (288) I 5.2 (0.4 - 121) 16

Depth above 100 m Intact rock (152) I 2.2 (1 - 7) 6 i

(41) l 6.6 (1 - 121) 17 R -structures

Depth range of 100 - 300 m (384) I 2.3 (0.3 - 27)

R-structures (128) i 4.3 (1 - 78)

7 Intact rock 13

Depth below 300 m Intact rock (870) I 2.0 (0.1 - 79) I R-structures (119) ! 5.5 (0.4 - 117) 19

5

Mica gneiss Intact rock (1085) I 2.2 (0.1 - 79) 6 R-structures (245) I 5.3 (0.4 - 121) 16

Granite/pegmatite Intact rock (249) I 1.9 (0.1 - 27) 4

R-structures (43) I 4.1 (0.5 - 34) 14 -------··------·- -·---·--·--·---·--~···-·-····--···-·----·-·-·---·-·-·······-····-·-········---···-··-·--····-··-··

Tonalite Total (55) I 1.6 (0.2 - 6) 2

Amphibolitelmetadiabase Total (17) I 0.9 (0.1 - 2) 0

The mean fracture width in the internal structures of the blocks is greater than the mean of all the fracture widths. This difference is thought to be due partly to few, very large fracture widths. In the internal structures the proportion of fractures having widths above 5 mm is considerably greater than in the intact rock. In both cases most of the fractures (67- 72 %) have widths between 1-5 mm. In structures R10, R11, R13, R14, R17 and R19 the mean width varies from 3.1-42 mm and most typical values are 4 - 7 mm or about 1.5 - 3 times greater than the mean width in the intact rock. The small total number of fractures combined to a single fracture with a large width explains the large differences in fracture widths between structures and intact rock. Most of the fractures with large widths belong to structures R10 and R17.

The fracture width does not appear to be depth-dependent in either the intact rock or in the R-structures. In the internal structures the mean width is twice as great as that in the intact rock. In the uppermost 100 m of the bedrock the mean width in the structures is three times greater than that of the intact rock. In the near surface zone 21 - 25 % of the fractures belong to internal structures and at depths greater than 300 m about 12 % of the fractures belong in this category.

Most of the observations are from mica gneiss, although significant differences between the rock types do not exist. Observations from amphibolite and tonalite are few and no internal structures are present within these rock types. In mica gneiss 18 % of the frac­tures and in granite/pegmatite 15 % of the fractures belong to the internal structures.

68

Most of the fracture width data are derived from blocks 4 and 5. The distributions of fracture widths per block are similar to those for the whole area and no significant differences between the blocks are observed. Internal structures are present only in blocks 4 and 5 (28% and 19% of the fractures respectively) and the mean width is about 5 mm. The mean width of the fractures included in the analysis referred to above varies between 2 - 3 mm. Fractures having widths > 5 mm constitute 3 - 9 % of all the fractures (the proportion being greatest in block 4) and in the case of fractures within internal structures the respective proportion is 14- 18 %.

Based on the analysis of fracture widths the bedrock at Olkiluoto was placed into the normal class of constructability. Fractures having a width over 5 mm are sparse, their number being greatest in some R-structures. No significant differences between blocks or rock types were observed and the fracture width is also not depth-dependent. The mean width of fractures within the internal structures of the blocks is notably higher than that for fractures in the intact rock.

69

4.3 Hydrogeological properties

4.3.1 Hydraulic conductivity of the intact rock

The evaluation of the hydraulic conductivity of the intact rock is based mainly on the results of the difference flow measurements measured over 2 m test lengths (PolHinen & Rouhiainen 1996a, 1996b ). In addition, some results of the constant head injection tests measured over 2, 7, 10 and 31 m test sections, have been used (HamaHiinen 1997 a, 1997b, 1997c, 1997d, 1997e, Kuusela-Lahtinen & Front 1991a, 1991b, 1991c).

The hydraulic conductivity (K) of the intact rock varies over the complete measurement range of the equipment used. The highest value measured (K2m) is 4E-4 m/s and the lowest value 6E-12 m/s. Most of the measured values are less than lE-10 m/s.

To analyse the depth-dependence of hydraulic conductivity, the data were divided into four depth classes, 0-200 m, 200-400 m, 400- 600 m and over 600 m (Fig. 4.3-1). The uppermost 200 m of the bedrock is clearly more conductive than that at greater depths. At depths greater than 200 m, over 90% of the measured values of hydraulic conductivity are less than 1E-10 m/s. The depth interval of 400- 600 m is hydraulically more conductive than the interval of 200-400 m. The reason for this could be due to the fact that the measurements over the depth interval of 400 - 600 m were performed closer to hydraulically-conductive structures than those in the depth interval of 200-400 m.

100%

95%

90% ~

-0- 200m, N =462 ~ .:: 85% -~ =

-200-400 m, N = 515

--*- 400 -600 m, N = 444 e = 80% u

"""*-- over 600 m, N = 466

75%

70% -10 -9 -8 -7 -6 -5

Hydraulic conductivity, log K (rnls)

Figure 4.3-1. The distribution of the hydraulic conductivity of the intact rock at Olkiluoto by depth interval (N = 1887).

70

The influence of the three major rock types (mica gneiss, granite/pegmatite and tonalite) on the hydraulic properties of the intact rock has been investigated and the results are presented in Figure 4.3-2. In the near-surface zone (0- 200 m) tonalite is most conduc­tive and over the depth intervals of 200-400 m and 400- 600 m mica gneiss is slightly more conductive than granite/pegmatite.

An analysis of the hydraulic conductivity of the blocks demonstrated that block 4 is most conductive with 77% of the samples within the block having a hydraulic conduc­tivity< 1E-10 m/s. This can be explained, however, by the fact that the borehole data (Table 2.4-3) in that block were from shallow depths. The values of hydraulic conduc­tivity in blocks 2, 5 and 8 are very similar. In these blocks, over 90 % of the values of the hydraulic conductivity are< 1E-10 m/s. In the other blocks, over 95% of the meas­ured values are < 1E-10 m/s, however the number of observations in these blocks is very small.

The spatial distribution and the transmissivities of the hydraulically most conductive features (single fractures or minor fracture zones of intact rock, excluding the R­structures) have been analysed, as these factors would have a notable effect on the con­structability. In this analysis the limit of transmissivity (T) was set to about 1E-8 m2/s and the separation of borehole sections having transmissivities greater than this limit were calculated. The lengths of the conductive sections were determined on the basis of measured values of K2m. If several neighbouring sections with anomalous T 2m values were present they were treated as one feature. The location of either the centre of the feature or its most conductive portion was used to calculate the separation from adjacent features and the transmissivity (T) of the feature was determined by summing the values

~ ~

-~ -eu = e = u

95%

90%

85%

80%

-10

........... GR/PG, N = 354

-MGN,N=l409

_._TON, N = 107

-9 -8 -7 -6 -5

Hydraulic conductivity, log K (rnls)

Figure 4.3-2. The relation between the rock type and the hydraulic conductivity of the intact rock at Olkiluoto (N = 1870). GRJPG = granite/pegmatite, MGN =mica gneiss, TON= tonalite, N = number of samples.

71

of T 2m of the measurement intervals associated with the feature. In the near-surface zone, in particular, this method is subjective, as hydraulically-conductive features are closely spaced and it is difficult to determine the boundaries of the features. The dis­tance between the boundary of an identified R-structure and a hydraulically-conductive feature, as well as the separation of R-structures containing no hydraulically-conductive features, were also taken into account in this analysis. The rock between R-structures was considered to be intact rock (Saksa et al. 1998).

The results of this analysis show that the separation of hydraulically-conductive features (upper part of Fig. 4.3-3) is approximately 14 m at shallow depths and increases to 140 m at a depth of 700 m. On average, the separation of hydraulically-conductive fea­tures in the depth interval of 400- 500 m is about 130 m, which differs notably from the regression line shown in the upper part of Figure 4.3-3. Two depth classifications were used; in case A the depth classes are 0- 100 m, 100- 200 m, 200- 300 m, 300-400 m, 400 - 500 m and over 500 m and in case B the classes are 0 - 100 m, 100 - 300 m and over 300 m. All the depths presented are true vertical depths, the reference level being sea level. The regression line shown in Figure 4.3-3 is the least-square fit using depth classification B, although it is also a reasonable fit to depth classification A. The use of depth classification B is justified by the fact that the sample sizes in case A are small, especially at greater depths (the sample total was 73). The greatest observed separation of hydraulically-conductive features was 278 m.

The transmissivities (logarithm of T values) of the hydraulically-conductive features found in the intact rock are shown in the lower part of Figure 4.3-3. In addition to the measured T values, the means of the four depth classes (0 - 100 m, 100 - 200 m, 200- 300 m and over 300 m) and their regression line are shown. There is only a weak correlation between the depth and T values and the reliability of the analysis is reduced by small sample size for the depth class of over 300 m.

From the constructability point of view, the intact rock at the planned repository depth range of 300 - 700 m at Olkiluoto is considered normal with regard to its hydrogeologi­cal properties. Over this range of depths the separation of hydraulically-conductive fea­tures varies from 60 m to 140 m. There seems to be no clear relationship between the hydraulic conductivity and the rock type or between the hydraulic conductivity and the block number. The uppermost 200 m of the bedrock is distinguished as being more con­ductive than the rock at greater depths, where the depth-dependence of the hydraulic conductivity is not that apparent.

4.3.2 Hydraulic conductivity of the A-structures

Hydraulic conductivity and the number of hydraulically-conductive fractures affect the constructability of the R-structures. The number of hydraulically-conductive fractures can be estimated mainly from the results of the borehole-TV measurements and the fracture mineral studies. Where no distinct estimate of the number of conductive frac­tures has been made, the results presented in the drilling reports are used - although these data can differ considerably from the other data used in estimating the number of hydraulically-conductive fractures. There are considerable uncertainties associated with

72

Distance (m) 0 1 0 20 30 40 50 60 70 80 90 1 00 11 0 120 130 140 150

0

100

200

300 -.§.. 400 .s::::: .., g. 500 c

600

700

800

900

0.00

100.00

200.00

300.00 e - 400.00 .s::::: .., c. Cl) 500.00 c

600.00

700.00

800.00

900.00

~

'

-9

~ ~

"' '

-8

~0 0 0/\. /\.

oo p 0 Oo s oo 0 0

<(11 V 0

<> • 0 e' 0

J

0 Depth classification A

• Depth classification B -

--Regression line (B)

~]

' ~ 0 ., '-

p '

-6 -5 -4

I ~ .. 0 <:o 0

~ 0 ~ (')

oo oo

V

0 Measured T values 0

Means • - Regression line (Means)

0 ~

Figure 4.3-3. Distance between hydraulically-conductive features in the intact rock (upper part) and their transmissivities with depth (lower part).

estimates of the hydraulic properties of individual fractures due to the general lack of precise measurements. In providing estimates of the number of hydraulically-conductive fractures, all open fractures are assumed to be hydraulically-conductive. Recent results of borehole testing indicate, however, that only a few of these are in fact conductive.

73

The other fractures are not necessarily tight, but their conductivity remains unknown, as the more conductive fractures are dominant. In the fractured sections of the rock, the density of hydraulically-conductive fractures is so great that it is impossible to distin­guish them from each other. In fractured sections it is also common for a few of the fractures to dominate the flow. The hydraulic conductivities of the R-structures and an estimate of the number of conductive fractures associated with them are presented in Appendix 2. In Figure 4.3-4 the transmissivities of the R-structures are shown as a function of depth.

log T (m2/s) -10 -9 -8 -7 -6 -5 -4 -3

0

R19 100

R9

200

300

R14 + R17

400 g J: 500 -c. Q)

c o VLJ boreholes 600 • KR boreholes

700 R20, (R21)

800

900

1000

Figure 4.3-4. Measured transmissivities of R-structures and their classification into four groups.

74

4.3.3 Water ingress and grouting properties

Estimates of the requirements for grouting the rock mass are based on hydraulic con­ductivity measurements in the boreholes. It was assumed that if the hydraulic conductiv­ity K ~ 1E-9 m/s grouting would not be required. Where 1E-9 m/s < K < 1E-8 m/s it was concluded that grouting could be needed, in which case an estimate of the grouting requirement would be made on a case-by-case basis during the excavation, and would depend on the width, hydraulic conductivity and location of the leakage zone and on the hydraulic properties of its fractures. If the hydraulic conductivity K ~ 1E-8 m/s the rock mass was classified as hydraulically-conductive and it was assumed that grouting would always be necessary.

The groutability of the rock and the potential grout take was estimated with reference to specific structures. The grouting requirements were based on estimates of groundwater ingress, on fracture data, on hydraulic conductivity measurements in boreholes (Appen­dix 2) and on the hydraulic interpretation presented in Section 4.3.2, as well as on the results of the grouting research project at Strip a (PolHi et al. 1994 ).

The estimates of groundwater ingress and groutability are subject to several uncertain­ties. There is not much practical information available regarding the use of the analyti­cal methods in estimating ground water ingress into tunnels. The interpretations of trans­missivity, groutability and grout take are subjective simplifications based on the results of borehole testing, which were sometimes carried out in very different parts of the same structure. Many factors affect the groutability and the grout take, such as the hy­draulic conductivity, the number of fractures, fracture properties and rheological prop­erties of the grout. In spite of these uncertainties, however, the transmissivity and the expected groundwater ingress are shown as single numerical values in Table 4.3-1.

Intact rock

On the basis of Figure 4.3-1 it can be estimated that about 10 % of the rock mass from the surface to a depth of 200 m possibly needs grouting, as its hydraulic conductivity lies in the range (lE-9 m/s ~ K ~ 1E-8 m/s) and 10% probably needs grouting. Over the depth interval of 200- 600 m about 3 - 5 % possibly needs grouting and 2 % probably needs grouting. In blocks 2, 5 and 8 about 5 - 8 % of the rock mass may need grouting. At depths greater than 600 m there is little need for grouting.

Estimates of groundwater ingress at different depths were made using Moye' s equation in reverse. It is normally used for the determination of hydraulic conductivity (Ylinen 1985) and the purpose here was to calculate values of ingress for the various possible depths for the repository. With Moye's equation the groundwater ingress Q is calculated as follows:

where

L·P·K·2·7r Q= L '

p·g·(1+ln(-)) 2·r

4.3-1

Q = groundwater ingress (m3/s) L = test interval (m)

75

P = overpressure (hydrostatic pressure) (N/m2)

K = hydraulic conductivity (m/s) p = water density (kg/m3

)

g = gravitational acceleration (m/s2)

r = radius of the tunnel (m)

In the calculation attention was also paid to the access shafts in addition to the proposed disposal tunnels. An assumption was made that all the hydraulically-conductive zones in the repository could be grouted to achieve a value of K = 5E-9 m/s. The following val­ues of groundwater ingress were obtained for three different depths:

- 300 m depth - 500 m depth - 700 m depth

Q = 270m3/day or about 0.71/minute/100 m of tunnel Q = 480 m3 /day or about 1.2 1/minute/1 00 m of tunnel Q = 430m3/day or about 1.0 1/minute/100 m of tunnel

In the uppermost 200 m of the bedrock about 20 % of the intact rock was placed in the demanding class of constructability with regard to its requirement for grouting. In the planned depth range for the repository of 300 - 700 m about 2 - 7 % of the rock mas was classified as demanding, implying the possible need for grouting. About 1 - 2% of the rock mass was classified as hydraulically-conductive (K > 1E-8 m/s), implying that grouting would probably be required. More than 90 % of the rock mass over the depth interval of 300 - 700 m was, therefore, placed into the normal class of constructability with regard to the need for grouting.

Structures

The calculation of groundwater ingress due to the R-structures (before grouting) is based on the interpretation of the transmissivity of these structures at a depth of 500 m (Figure 4.3-4 ). The estimated ground water ingress was calculated for each structure using equation 4.3-2 (Alberts & Gustafson 1983). The estimates presented in Table 4.3-1 are approximate and should only be used as a guide.

where

21Ch · /( · L Q = ln4h/2r '

4.3-2

Q L K h r K·L

= = = = = =

water ingress (m3/s) width of fracture zone (m) hydraulic conductivity (m/s) hydrostatic pressure expressed as the height of a water column (m) radius of tunnel (m) transmissivity T (m2/s)

The formula above is based on Thiem's well equation, and assumes that the tunnel intersects the structure at a great depth, in which case the radius of influence of the flow

76

R = 2h (Alberts & Gustafson 1983). The radius of the tunnel is taken to be 2 m and it is assumed that it intersects the structure at a depth of 500 m.

The predicted groundwater ingress due to the R-structures varies between 0- 300 1/min before grouting (Table 4.3-1 ). The largest ground water ingress is expected from struc­ture R20 and possibly also from structure R21. The estimated groutability of the struc­tures is usually moderate or difficult. In structures R20 and R21 a moderate to large grout take is expected.

Based on the estimated need for grouting and the groutability of the structures, the fol­lowing structures were placed into the normal class of constructability: R2, R9, R10, R13, R14, R15, R17 and R30. The fracture R26 was classified as demanding and the structures Rl, Rll, R12, R19, R20, R21 and R24 were classified as very demanding.

Table 4.3-1. The grouting properties of the R-structures. Tsoom = the interpreted trans­missivity at a depth of 500 m.

Structure/ Tsoom Estimated Estimated Estimated Estimated Property (m2/s) water ingress groutability need1

) for grout take (1/min) grouting ------------------··-·----------·-----·-·----·-·------···-··--·-·····--······ .. ·--··-···--···---·--·-

Rl 8E-7 20 moderate - difficult + moderate

R2 7E-8 2 moderate ± small

R9 7E-8 2 moderate - difficult ± small

RlO 7E-8 2 difficult ± small

Rll 8E-7 20 difficult + moderate

R12 8E-7 20 difficult + moderate

R13 5E-9 < 1 difficult small

R14 5E-9 <1 difficult small

R152) 5E-9 <1 (difficult) small

R17 7E-8 2 difficult ± small

R19 8E-7 20 moderate - difficult + moderate

R20 1E-5 300 moderate - difficult ++ moderate - big

R21 8E-7 (lE-5) 20 (300) moderate - difficult ++ moderate - big

R24 8E-7 20 moderate - difficult + moderate

R26 8E-7 20 good - moderate + moderate

R303) not defined (small) (difficult) (-) (small)

1) Need for grouting:- none,± possible,+ probable,++ very probable 2) Missing fracture data 3) Transmissivity is not defined, hydraulic conductivity is assumed to be small (Section 4.3.2, App. 2)

77

4.4 Structural rock type

4.4.1 General

The structural rock type defines the quality of a rock mass using the most significant factors affecting its constructability. These factors are considered to be the lithological properties, the hydrogeological properties and the properties of the fractures (see Sec­tion 3.2). The following structural rock types have been defined: i) intact rock, ii) frac­tured rock, iii) crushed rock and iv) hydraulically-conductive rock, and their properties are described in Table 3.2-2.

The division of the bedrock into these structural rock types was examined separately for the intact rock of the bedrock model and for the R-structures. The examination of the first three structural rock types was made with reference to the rock type, to each block and to each borehole. The intact rock of the bedrock model is also classified predomi­nately as intact rock in terms of its structural rock type, even though it can also include some fractured, crushed or hydraulically-conductive borehole intersections because all such intersections have not been modelled as R-structures. The differences between the intact rock of the bedrock model and the intact rock determined by its structural rock type are insignificant in practice and for this reason they are not distinguished elsewhere in this report.

4.4.2 Intact, fractured and crushed rock types

The examination of the structural rock type was based on drill core investigations (Suo­men Malmi Oy 1989a, 1989b, 1989c, 1990a, 1990b, Rautio & With 1991, Jokinen 1994, Rautio 1995a, 1995b, 1995c, 1996a, 1996b ). All the rock which is not fractured, crushed or classified as "core loss" was placed into the category of intact rock. The fractured rock category includes all the rock which in the borehole reports was placed into the Riiii class according to the Finnish Engineering Geological Rock Classification system. The crushed rock category includes all the rock which was placed into the RiiV class and also the strongly or completely weathered rock (Rp2- Rp3). All the core loss which was not unambiguously caused by the drilling process, or which was not placed in the Ri or Rp classes, was termed unclassified core loss. In places where the core material was placed into a range of Ri classes the rock was classified according to the worst class.

The distribution of the intact rock of the bedrock model between the structural rock types when examined according to its lithology and its presence in different blocks and boreholes, is presented in Tables 4.4-1 - 4.4-3. The division of the R-structures of the bedrock model into the structural rock types is presented in Table 4.4-4. The rock listed as being outside the blocks in Table 4.4-2 includes all the borehole data that is physi­cally outside the boundaries of the blocks.

78

Table 4.4-1. Distribution of the intact rock of the bedrock model between the structural rock types according to lithology.

Lithology/ I Core Intact Fractured Crushed Unclassified Structural I length rock rock rock core loss rock type I (m) (%) (%) (%) (%)

Mica gneiss I 4020 99.1 0.6 0.0 0.3 I Granite/ I 896 99.5 0.1 0.0 0.4 !

pegmatite I Tonalite ! 370 100.0 0.0 0.0 0.0 I Amphibolite/ I 41 99.8 0.2 0.0 0.0 I

metadiabase I

Table 4.4-2. Distribution of the intact rock of the bedrock model between the structural rock types according to their presence in the various blocks.

Block/ Core Intact Fractured Crushed Unclassified Structural length rock rock rock core loss rock type (m) (%) (%) (%) (%)

Block 1 57 100.0 0.0 0.0 0.0

Block 2 431 100.0 0.0 0.0 0.0

Block 4 1908 99.4 0.5 0.0 0.1 Block 5 1664 98.9 0.5 0.0 0.6

Block 6 231 100.0 0.0 0.0 0.0 Block 7 72 99.2 0.8 0.0 0.0

Block 8 508 98.5 1.5 0.0 0.0 Block 9 81 96.4 0.0 0.0 3.6 Block 10 160 99.1 0.9 0.0 0.0 Outside the 215 100.0 0.0 0.0 0.0 blocks

The distribution of the R-structures into the structural rock types was calculated both in metres (the average lengths of the borehole intersections) and as percentages. If the summed core length of the fractured and crushed rock types of an R -structure was at least 3 m, which is about the length of one excavation round when tunnelling in a frac­ture zone, it was considered significant (in bold in Table 4.4-4 ). The calculation method did not consider the possibility as to whether the borehole intersections associated with a specific structural rock type were equally distributed into different boreholes or whether they occurred as one longer or several shorter intersections.

The locations of the boundaries of the R-structures in the bedrock model significantly affect the percentage distribution of the structural rock types in the R-structures. As the proportion of the intact rock in the bedrock model is considerably larger than that in­cluded as structures, the boundaries of the R-structures will not usually have much ef­fect on the percentage distributions of the structural rock types within them.

79

All the rock types at Olkiluoto (the intact rock of the bedrock model) contain only a small proportion of the fractured rock type and none at all of the crushed rock type. The proportion of the intact rock type is > 99 % in all of the rock types (Table 4.4-1) and no differences between the different rock types can be detected.

The distribution of the structural rock types of the intact rock of the bedrock model is essentially similar, whether it is considered with reference to the block or the borehole number (Tables 4.4-2 and 4.4-3). The only anomalous feature is the unclassified core loss of about 4 % in borehole KR6, which also intersects block 9.

In the R-structures (Table 4.4-4) the fractured rock type and/or the crushed rock type are present in significant amounts in structures R9, R12, R17, R20, R21 and R24 as well as in the unmodelled structures (RX).

Table 4.4-3. Distribution of the intact rock of the bedrock model between the structural rock types according to the boreholes which intersect it.

Borehole/ Core Intact Fractured Crushed Unclassified Structural length rock rock rock core loss rock type (m) (%) (%) (%) (%)

,... ____ ....,..,... ______ ......... ------·~ ..... ·---···---·..--·-~-..---·-·-----..-··--·~ ...... ~-·-··-··----~-·-----· KRl 880 99.8 0.2 0.0 0.0

KR2 949 98.5 1.5 0.0 0.0

KR3 410 99.7 0.3 0.0 0.0

KR4 761 99.6 0.3 0.0 0.1

KRS 466 100.0 0.0 0.0 0.0

KR6 282 94.5 1.1 0.0 4.4

KR7 262 99.1 0.7 0.0 0.2 KRS 252 99.9 0.1 0.0 0.0 KR9 513 99.8 0.2 0.0 0.0 KRlO 552 99.8 0.2 0.0 0.0

80

Table 4.4-4. Distribution of the structures of the bedrock model between the structural rock types. L = drilling length, N = number of borehole intersections, RX refers to unmodelled structure intersections.

Structure/ L N Intact I Fractured I

Crushed Unclassified Structural (m) rock I rock rock core loss

I i

rock type (m(%)) (m(%)) i (m(%)) (m(%)) !

RX 148 19 3.1 (40.4) I 4.6 (58.6) ! 0.1 (1.0) 0.0 (0.0) i I i Rl 12 3 2.0 (49.8) I 2.0 (50.3) 0.0 (0.0) 0.0 (0.0) I I I I

R2 18 1 16.8 (93.1)

I 1.3 (6.9) 1 0.0 (0.0) 0.0 (0.0)

R9 24 2 6.6 (55.1) 5.4 (44.9) I 0.0 (0.0)

I 0.0 (0.0)

I

RlO 60 3 18.0 (89.8) I 2.0 (10.1) I 0.0 (0.0) 0.0 (0.1) I

I Rll 6 1 4.7 I

1.3 ! 0.0 0.0 (78.7) I (21.3) ~

(0.0)

I (0.0)

R12 10 1 6.7 (67.4) I 3.3 (32.6) i 0.0 (0.0) 0.0 (0.0) ! I

I I l

R13 10 1 7.3 (72.9) 2.7 (27.1) 0.0 (0.0)

I 0.0 (0.0)

R14 2 1 1.3 (64.5) I 0.7 (35.5) I 0.0 (0.0) 0.0 (0.0)

R15 2 1 0.5 (22.5) I 0.0 (0.0) I 1.6 (77.5) 0.0 (0.0)

R17 45 3 10.1 (67.1)

I 3.7 I 1.2 0.0 (24.7) I (8.2) (0.0)

R19 11 3 2.0 (53.3) 1.2 (32.1)

I 0.5 (14.6) 0.0 (0.0)

R20 66 4 12.7 !

1.1 (77.2) i 2.7 (16.4) (6.4) 0.0 (0.0)

R21 70 4 12.5 (71.3) I 3.4 (19.6) l 1.5 (8.8) 0.0 (0.3)

R24 39 2 16.3 (83.4)

I 3.1 (15.9) i 0.1 (0.6) 0.0 (0.0) I

R26 14 4 3.2 (92.4) 0.3 (7.6) I 0.0 (0.0) 0.0 (0.0) i

R30 5 1 3.5 (70.2) ! 1.5 (29.8) ! 0.0 (0.0) I 0.0 (0.0) i I ! I

4.4.3 Hydraulically-conductive rock type

The bedrock is considered hydraulically-conductive when the measured or estimated hydraulic conductivity is so high that grouting is required. On the basis of analytical calculations the bedrock was defined as being hydraulically-conductive if the values of hydraulic conductivity were> lE-8 m/s.

The hydraulic conductivity of the R-structures can be estimated on the basis of Figure 4.3-4. The structures R13 and R14 do not belong to the hydraulically-conductive rock type based on the measurements and the depthltransmissivity relationship presented in Figure 4.3-4. The transmissivity of these structures is estimated to be nearly lE-8 m2/s at a depth of 500 m and, as the thickness of the structures is at least one metre, their av­erage hydraulic conductivity remains below the above mentioned limit (K = lE-8 m/s). All other structures belong to the hydraulically-conductive rock type, although the mean conductivity of structures R2, R9, RlO and R17 is about K = lE-8 m/s or less. Within these structures, however, only one or a few highly conductive 2 m borehole sections are observed. As grouting is needed in these sections the structures were defined as hydraulically-conductive.

The hydraulic conductivity of the intact rock is discussed more thoroughly in Section 4.3.1. Conductive features, which can be either single fractures or minor fractured

81

sections, with values of transmissivity > lE-8 m2/s, are present with separations of 14- 140 m, with the separation increasing with depth (Figure 4.3-3). At a repository depth of 500 m the mean separation of conductive features is approximately 100 m. In contrast, all the uppermost 100 m of the bedrock is classified as hydraulically­conductive, because its mean hydraulic conductivity is> lE-8 m/s.

4.4.4 Constructability

All the rock types and blocks (the intact rock of the bedrock model) are placed mainly in the normal class of constructability with regard to their structural rock type. This is due to the fact that their schistosity is not well developed and there are not many zones of fractured rock intersected in boreholes that are not included in R-structures. A more prominent schistosity is developed in about 20 % of the rock and, in these cases it is classified as demanding, if the tunnel is oriented close to the plane of the schistosity. More hydraulically-conductive rock is found on average at 100 m intervals at a depth of 500 m and its constructability classification is based on the amount of groundwater ingress/lOO m of tunnel (Table 3.3-4).

The R -structures may belong to more than one structural rock type on the basis of their properties, for example they may belong simultaneously to the fractured rock type and to the hydraulically-conductive rock type. Where this was the case they were given a classification which gave the worse class in terms of their constructability. The struc­tures were classified as follows with regard to the structural rock type: structures R2, RlO, R13, R14, R15 and R30 were placed into the normal class of constructability; structures R9, R 17, R26 and the unmodelled structure intersections (RX) were classified as demanding; and structures Rl, Rll, R12, R19, R20, R21 and R24 were classified as very demanding. Structure R19 is present only at shallow depth and structure Rll has been interpreted to continue to a depth not greater than 400 m. In both cases the pres­ence of these two structures will not affect the location of tunnels at greater depths than those indicated.

82

4.5 In situ stresses

4.5.1 Principal stresses

The in situ stress has been measured in four boreholes at Olkiluoto over a depth interval of 300 - 800 m (Klasson & Leijon 1990, Ljunggren & Klasson 1996). Measurements were made successfully using the hydraulic fracturing method at 31 locations in bore­holes KR1, KR2, KR4 and KR10. The in situ stress was also determined at 15 locations using the overcoring method in borehole KR10 over the depth intervals of 302- 333 m, 444- 453 m and 595- 614 m. In analysing the results of the overcoring method the average values obtained in the three depth intervals were taken into account.

Linear regressions of the maximum ( <J"H) and minimum ( crh) horizontal stress and the vertical stress (crv) (Fig. 4.5-1) are given by the following equations (in which Z = verti­cal depth from the earth's surface in metres and R = correlation coefficient):

crH = 0.06Z - 2.0 MPa

crh = 0.03Z + 0.9 MPa

crv = 0.03Z- 5.1 MPa

R= 0.89

R = 0.91

R = 0.83

4.5-1

4.5-2

4.5-3

On the basis of a linear extrapolation, the values of crH and crv at the surface would be negative, which is unlikely. According to the measurements made close by the reposi­tory of low- and intermediate-level waste (VLJ) the value of crH changes with depth ac­cording to equation 4.5-4, which is thought to be representative to a depth to 300 m:

O"H = 0.041Z + 2.67 MPa R = 0.70 4.5-4

The average horizontal stress ratio ( crH/crh) is 1.8, which is a typical value for Finland at a depth of 500 m (Tolppanen & Johansson 1996). The predominant orientation of crH is east-west, based on the results of the hydraulic fracturing method, however, even north­west-southeast and north-south directions have been measured. The average dip of the maximum principal stress (cr1) is 24° (with a range of 3- 34°). The average and standard deviation of the magnitudes of the horizontal and vertical stress measurements at Olki­luoto are presented for three depths of 300 m, 500 m and 700 m in Table 4.5-1.

50

45

40

35

li 30 ll.

~ f/l 25 f/l

~ ~ 20 en

15

10

5

0

0

• Sig-H

• Sig-h

"' Sig-V • • • Linear (Sig-V)

- -Linear (Sig-h)

--Linear (Siq-H)

crH: y = 0.056 Z- 1.98, R2 = 0.79, Z > 300 m

crh: y = 0.028 Z + 0.94, R2 = 0.83

crv: y = 0.034 Z- 5.05, R2 = 0.68 •

83

••• •

• •

• • • ••

• • •

• .. _._.,

--- : I._ _..--a -- .. • a.! - -

100 200

• • • ..... ~- • 11 ,..,... ..... . ~~ -- .· ,,. _.-·

. ! . - ...

300 400 500

Depth (m)

600 700 800

Figure 4.5-1. Depth dependence of the stress components at Olkiluoto.

900

Table 4.5-1. Mean in situ stresses at Olkiluoto (standiird deviation) at depths of 300 m, 500 m and 700 m.

Depth/Stress O'H ah av crH-direction (MP a) (MP a) (MP a) e)

Bedrock surface (from 2.7 extrapolation)

Depth level 300 m 15 .3 8.7 7.9 92.2

(depth range 296-339 m) (3 .1) (2.0) (2.0) (46.7)

Depth level 500 m 24.7 14.6 10.2 88.9

(depth range 442 - 598 m) (5 .9) (3 .0) (6.0) (28.2)

Depth level 700 m 36.4 20.4 16.8 93 .8

(depth range 601 - 804 m) (10. 7) (4.0) (4.7) (32.5)

84

4.5.2 Strength/stress ratio

The stability of the rock mass was investigated using data for the mica gneiss by exam­ining the ratio of the uniaxial compressive strength of the rock (UCS) and the maximum horizontal stress (crH). It has been noticed empirically (Grimstad & Barton 1993) that a tunnel can be excavated without constructional problems when the ratio UCS:crH > 10. When this ratio lies in the range 5- 10, spalling of the rock can occur and when in the range 3 - 5 moderate spalling is possible. When the ratio < 3 rock bursts and related problems are likely. The investigation of this ratio was carried out using parameter values which are independent of the form of the distribution functions for stress and strength - the lower quartile, median and upper quartile of the distributions (Table 4.5-2). The ranges of the strength/stress ratio using the lower quartile and upper quartile curves (Figure 4.5-2) were calculated using the lower and upper quartiles for the strength of mica gneiss and the maximum horizontal stress, so that the most advanta­geous (UCSmaxlcrHmin) and least advantageous (UCSmin/crHmax) ratios were obtained.

30 Mica gneiss

25 · · • · "lower quartile

----+---median

20

:I: · · • · · upper quartile

b -tJ) 15 0 ::>

10

5

3

0

200 300 400 500 600 700 800

Depth (m)

Figure 4.5-2. Ratio of uniaxial compressive strength (UCS) of mica gneiss and the maximum horizontal stress ( aH) as a function of depth. The colour bar on the right indicates the effect of the strength/stress ratio on the stability of the rock mass.

85

Table 4.5-2. Statistical indicators of the uniaxial compressive strength (UCS) and maximum horizontal stress ( aH) (measured at three depths)for mica gneiss.

Statistics/ I ucs cr8 at different depths (MPa)

Property (MP a) 300m SOOm 700m _ _..

Upper quartile 124.2 16.8 29.1 43.7

Median , 112.0 I 13.7 24.1 38.8

Lower quartile J 90.2 I 13.1 21.3 28.3

When the minimum horizontal stress ( crh) is normal to the long axis of tunnels the stress concentration around a deposition tunnel and a hole is smaller than if the tunnel long axis were perpendicular to crH. Whatever the layout of the repository, some of the tun­nels would always be approximately perpendicular to crH.

The stability of a tunnel is least when O"H acts perpendicular to its long axis. In such a situation the mica gneiss was placed, on the basis of its strength/stress ratio, into the normal class of constructability to a depth of 340 m, in the demanding class over the depth interval 340 - 520 m and in the very demanding class at greater depths (Table 4.5-3). On the basis of their strength properties, tonalite and amphibolite/metadiabase are comparable with mica gneiss from the constructability point of view and granite/pegmatite is slightly better.

When evaluating the results, it should be remembered that values of the maximum hori­zontal stress ( crH) were used instead of values of the maximum principal stress ( cr1). The average dip of cr1 is 24°, which means that the resolved component of cr1 in the horizon­tal plane (i.e. crH) is about 10% less than the value of cr1. Attention needs also to be paid to the variation in the measured values of the in situ stresses and the strength values of the mica gneiss.

Table 4.5-3. Variation of stress conditions in mica gneiss as a function of depth interpreted on the basis of the lower quartile curve of its strength/stress ratio (the most unfavourable situation).

Strength/stress ratio (UCS/cr8 )

Stabile (> 10)

Probable spalling (5 - 10)

Moderate spaDing (3 - 5)

Rock burst(< 3)

Depth limits (m) -----------

<250m

250-340 m

340-520 m

>520m

86

4.6 Groundwater chemistry

4.6.1 General

The hydrochemical characterisation of the surface water and groundwater is based on samples of precipitation, surface waters and groundwaters taken over the period 1988- 1997. The hydraulic conductivity of the bedrock decreases notably below a depth of 200 - 250 m (Ahokas et al. 1996) and, therefore, in this study hydrochemical data are divided into surface waters (sampled from springs, lakes, brooks, ponds, domestic wells and groundwater pipes), shallow groundwaters at less than 200 m depth (sampled from percussion drilled and cored boreholes) and deep ground waters below 200 m depth (sampled from cored boreholes). In this section, the sample depth refers to the borehole length, not the true vertical depth, which will always be less than the borehole length in inclined boreholes.

The bedrock at Olkiluoto contains fresh groundwater (Total Dissolved Solids (TDS) < 1 g/1; Davis 1964), brackish groundwater (1 g/1 < TDS < 10 g/1) and saline ground­water (TDS > 10 g/1). The present maximum observed salinity is about 70 g/1 from borehole KR4 in the depth interval 861 - 866 m. The hydrochemical parameters and their limit values considered in terms of the constructability of the bedrock are listed in Table 3.3-6.

4.6.2 pH values

The pH values increase with depth (Ruotsalainen & Snellman 1996). Surface waters and shallow groundwater still contain C02 dissolved from the atmosphere and produced by microbiological activity in the overburden. Thus the pH of the groundwater near the surface varies from 5.2 to 7.6, being slightly acidic, neutral or slightly alkaline. The pH values of the deep groundwater (range of pH 7.5- 9.0, i.e. almost neutral or clearly al­kaline) are indicative of water-rock interactions. This is especially obvious in the case of the high pH values of 8.3- 9.0 for the samples from borehole KR5, which are due to the presence of mafic minerals in the mica gneiss and granite or pegmatite (Gehor et al. 1996, 1997). The higher pH values in the deep groundwater is interpreted to be the re­sult of carbonate reactions and hydrolysis of silicate minerals (Pitkanen et al. 1998).

At Olkiluoto the pH of all groundwater sampled from below 200 m depth (Fig. 4.6-1) is greater than 5.5. In terms of the pH of the groundwater, the constructability of the bed­rock was classified as normal.

4.6.3 Sulphate content

The sulphate content (S04) of the Olkiluoto groundwaters varies considerably with depth, reflecting the subaqueous position of the site during the saline periods of the Baltic Sea (the Yoldian Sea, which was present from about 10000- 9500 BP and the Li­torina Sea, from about 7500-2500 BP, Eronen & Lehtinen 1996).

The maximum S04-concentration (523 mg/1) of all the surface and groundwater samples (Figure 4.6-2) lies near the limit value of 600 mg/1. The sulphate content of the ground-

87

water is not likely to increase and, on the contrary, will probably decrease as a result of dilution due to the mixing of different types of ground waters or as a result of microbio­logical processes. Sulphate reducing bacteria have been observed in the groundwater at Olkiluoto (Haveman et al. 1998).

The S04 concentrations of all surface and groundwater samples at Olkiluoto (Figure 4.6-2) are below the limit of 600 mg/1, so, based on the sulphate content, the constructa­bility of the rock mass was classified as normal.

0

100

200

300 -e 400 -.c 500 -c. ~ 600 ~

700

800

900

1000

I ~ ~ ~~!K Ll11&. 1111

"' •• .. "1! -

• • -~

• --••

•

2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12 .0

pH

::K Surface waters

11 Shallow ( < 200 m) grooodwaters

• Deep (> 200 m) grooodwaters

- Limit values

Figure 4.6-1. Depth distribution of pH values of shallow and deep groundwaters at Olkiluoto. The pH limit values 4.5 and 5.5 are marked with red lines.

-e -.c -c. ~

~

0

100

200

300

400

500

600

700 4

800

900

1000

0.1

•

~ '?f..~ "' :l( 11

AA A

~ I!

• • ••• -. • • - ~ .. .. • • .

1.0 10.0 100.0

S04 (mg/1)

• '"A

M -. -

1000.0 10000.0

::K Surf ace waters

11 Shallow ( < 200 m) grooodwaters

• Deep(> 200 m) grooodwaters

- Limits

Figure 4. 6-2. Depth distribution of SO 4 content of shallow and deep groundwaters at Olkiluoto. The limit values S04 = 600 mg/1 and S04 = 3000 mg/1 are marked with red lines.

0

100 :X ~"" 6.

U:,.k.i!.

200 A

• 300

t •• •• -e 400 - • .c 500 - -c. ~ 600 ~

• ••• • 700

• -800

900 4 •

1000

0

If': ~ .....

Ll

10 20 30 40

C02, free (mg/1)

88

50 60

::K Surface W<lters

6. Shallow ( < 200 m) groundW<lters

• Deep (> 200 m) groundW<lters

- Limits

Figure 4.6-3. Depth distribution of C0 2, free content of shallow and deep groundwaters at Olkiluoto. The limit values C0 2, free = 30 mg/l and C0 2, free = 60 mgll are marked with red lines.

4.6.4 Free carbon dioxide

The amount of free carbon dioxide (C02, free) in a ground water sample is in inverse pro­portion to its residence time in the superficial deposits and the bedrock. Rainwater is in equilibrium with the atmospheric gases, including carbon dioxide. In the superficial de­posits fresh groundwater, rich in carbon dioxide, dissolves ions from minerals, resulting in a decrease in its C02, free content due to geochemical reactions, e.g. the precipitation of calcite. There is an obvious trend of decreasing C02, free content with depth in the groundwater samples at Olkiluoto (Pitkanen 1994, Pitkanen et al. 1996, 1998, Ruotsa­lainen & Snellman 1996).

The free carbon dioxide content of shallow and deep groundwaters at Olkiluoto (Figure 4.6-3) is in most cases below the limit value 30 mg/1, so the constructability of the bed­rock was classified as normal with respect to this parameter.

4.6.5 Ammonium content

The ammonium found in the groundwaters is probably due to the anaerobic degradation of ancient organic compounds. A great number of the water samples have an ~ con­tent in the range of 0.01 - 0.1 mg/1, which is below the analytical detection limit. The local maximum~ content in deep groundwater is 0.39 mg/1.

The~ contents of all samples representing surface waters or groundwaters at Olki­luoto (Figure 4.6-4) are significantly below the limit value of 30 mg/1, so the constructa­bility of the rock mass was classified as normal with respect to this parameter.

-a -.c ...... c.. QJ

~

0

100

200

300

400

500

600

700

800

900

1000

0 .0 1

X "'~"' All.~ ~

ll.ll.ll.

• • • -- • • • : • ... • ··-

• • ~

• •

0.10

::1(

Ll.

A

•

ll.ll. F

•

1.00

NH4 (mg/1)

89

10.00 100 .00

X Surface waters

ll. Shallow ( < 200 m) groundwaters

• Deep (> 200 m) groundwaters

- Limits

Figure 4. 6-4. Depth distribution of NH4 + contents of shallow and deep groundwaters at Olkiluoto. The limit values NH4 + = 30 mg/1 and NH4 + = 60 mg/1 are marked with red lines.

4.6.6 Magnesium content

The Mg content of groundwater at Olkiluoto increases with depth, which is indicative of water-rock interaction and a component of deep brine within the groundwater samples (Pitkanen et al. 1996, 1998, Snellman et al. 1998).

The Mg content of all samples of surface waters and groundwaters at Olkiluoto (Figure 4.6-5) is below the limit value of 300 mg/1, so the constructability of the rock mass was classified as normal with regard to the magnesium content of the groundwater.

4.6.7 Chloride content

High chloride contents found in groundwaters can originate from water-rock interaction, as a consequence of the present Baltic Sea (in coastal area) or as a result of the site being submerged in the past during periods when the Baltic Sea was saline (Pitkanen et al. 1996, 1999, Snellman et al. 1998). The chloride content of the groundwater samples varies strongly as a function of depth, with the maximum chloride content being found in a sample from the base of borehole KR4 (861 - 866 m; Clmax = 43000 mg/1, Clmed = 8450 mg/1). This confirms the assumption that previous saline periods of the Baltic Sea have affected the composition of the groundwaters, as the chloride content of modern Baltic Seawater is about 3000 mg/1.

The increase in the chloride content of groundwater with depth indicates, therefore, not only water-rock interaction but also an increase in mixing with the deep brines (Pitka­nen et al. 1996, 1998, Snellman et al. 1998, Ruotsalainen & Snellman 1996).

0 .......... ?(~ ...

100 &

200

300 ... --a 400 -.::: 500 ..... Q. ~ 600 ~

700

800

900

1000

1.00 10.00

X

-~ ..

• •

... 1 .. ... "' • • I

• -• ·--• --

~

100.00

Mg (mg/1)

90

1000.00 10000.00

): Surface waters

.A. Shallow ( < 200 m) groundwaters

• Deep(> 200 m) groundwaters

- Limits

Figure 4. 6-5. Depth distribution of Mg2+ contents of shallow and deep groundwaters at

0/kiluoto. The limit values Mg2+ = 300 mg/1 and Mg2

+ = 1500 mg/1 are marked with red lines.

Only the freshest surface waters and groundwater of Olkiluoto (Figure 4.6-6) have chlo­ride contents below the limit value of 1000 mg/1. A significant part of the shallow and deep groundwater lies between the limit values, with a considerable portion also above the limit of 4000 mg/1 (Figure 4.6-6). The constructability of the bedrock to a depth of 400 m depth was classified as demanding with respect to its chloride contents and the bedrock below 400 m was classified as being very demanding.

0

100

200

300 -a 400 -.::: 500 .... Q., ~ 600 Q

700

800

900

1000

~ [A~ ~· <> ..

n .. ~ ~ ~ r

<>c

<> OO<JD -0 -

• • 6 ..

0 5000 10000 15000 20000 25000 30000 35000 40000 45000 Cl (mg/1)

;!( Surface waters

• KR1 /:;. KR2

<> KR3

.& KR4 0 KR5

+ KR8 0 KR9

- KR10 - Limits

Figure 4. 6-6. Depth distribution of er content of shallow and deep groundwaters at 0/kiluoto. The limit values er = 1000 mg/1 and er = 4000 mg/1 are marked with red lines.

91

4.6.8 Radon content

Dissolved gaseous radon (Rn-222) is found in the groundwater of granitic bedrock and is formed from the disintegration of radioactive uranium. The radon content of the Olki­luoto water samples varies greatly, because the local geological and hydrogeological conditions have a significant influence on the radon values. The maximum radon content observed is from the percussion borehole PR2 at a depth of about 15 m (Rn-222 = 1020 Bq/1). The maximum radon content observed in deep groundwater from the cored boreholes is 160 Bq/1.

The Rn-222 content of the groundwater decreases with depth and has been interpreted as being due to the reducing hydrochemical conditions at depth, with the result that U(IV) in the bedrock is not readily dissolved from the rock matrix into the groundwater (Ruotsalainen & Snellman 1996).

The radon contents of both shallow and deep groundwaters at Olkiluoto (Figure 4.6-7) is below the limit of 500 Bq/1 so, in this respect, the constructability of the rock mass was classified as being normal.

0 ~ "' 100

200

300 • -e 400 . '-' .c 500 .......

.. . c. ~ 600 ~

700 • 800

900

1000

10

"'"'~"" ~ JI..JI.. .lt.ail.. ...

... - ... ii..JI.. Jl.. ....

• • •• - - -• • .. •

.. • •

100

Rn-222 (Bq/1)

1000 10000

~ Swf ace waters

.._ Shallow ( < 200 m) groundwaters

• Deep (> 200 m) groundwaters

- Limits

Figure 4.6-7. Depth distribution of Rn-222 content of shallow and deep groundwater at Olkiluoto. The limit values Rn-222 = 500 Bqll and Rn-222 = 2000 Bqll are marked with red lines.

92

4.7 Rock engineering properties

4.7.1 Drillability

The drilling parameters DRI (Drilling Rate Index) and CAI (Cerchar Abration Index) have been determined only for mica gneiss and tonalite at Olkiluoto (Table 4.7-1). The estimation of those parameters for the other rock types has been made on the basis of a literature review. The Vickers hardness of the rock types were calculated on the basis of the average mineral composition calculated from thin section analysis and the Vickers hardness of the following rock forming minerals: quartz 1060, plagioclase 800, potas­sium feldspar 730, mica (biotite) 110, amphibolite (hornblende) 600 and cordierite 1170.

In tunnelling the drilling properties of the rock types were estimated by means of the parameters mentioned above and no significant differences were found between them. Amphibolite/metadiabase was somewhat less abrasive than the other rock types (as it has the smallest Vickers hardness), however the drilling rate (DRI) was only marginally lower.

The intention is to drill disposal holes in the repository using the full face boring method and the rock types of Olkiluoto were divided into different strength classes for the estimation of their drillability, since this is directly related to the compressive strength. Tonalite and amphibolite/metadiabase are classified as weak in terms of their strength and mica gneiss and granite/pegmatite as weak to moderate (Table 4.7-1). On the basis of the compressive strengths it is estimated that the average drilling rate in to­nalite and amphibolite/metadiabase is a little higher than in mica gneiss and gran­ite/pegmatite.

According to a Finnish manufacturer of drilling equipment (Lislerud & V ainionpaa 1997), the drilling rate in a weak rock is double that of an extremely strong rock and, in this context, it is considered that tonalite and amphibolite/metadiabase would be classi­fied as being easy to drill and mica gneiss and granite/pegmatite easy or normal. If, however, a comparison of the drillability of the rock types is made using the DRI index, as has been recommended from the results of test drilling in the research tunnel at Olki­luoto (Autio & Kirkkomaki 1996), there would appear to be no significant difference between the rock types in this respect.

The quality of the rock within the fracture zones, most of which are modelled as R­structures in the rock model, may cause a decrease of the drilling rate during tunnelling. The disposal holes will be drilled only in intact rock, whose presence will have been confirmed from pre-investigation drilling.

With regard to the drilling properties, all the rock types at Olkiluoto were placed in the normal class of constructability, regardless of the drilling method.

93

Table 4. 7-1. Drilling parameters and calculated Vickers hardnesses according to the mineral composition.

Rock type/ DRI 1) I DRI 2) CAI 1) Strength Vickers Vickers

Property index index index (MP a) (average) (range) (defined) (literature) ---------··-r---·-·----.. - >-··-······-·-·----·

Mica gneiss 45 50-70 4.3 80- 140 713 382- 948

(s = 4.3) (s=0.1) I Granite/ - 45 - 65 (gr) - 115- 150 I 807 720- 895 pegmatite I 55-75 (pg) I

I

Tonalite 55 3)

I 45-65 3.7 3) 80- 110 I 672 535- 822 i

(s = 3) (gr) 4) (s = 0.4) I !

Amphibolite/ I !

-I

40- 60 (atb) 100 I 559 410-708 metadiabase I 30-45 (db) I

1) Johansson & Autio 1995 2) Naapuri 1995 3) Tonalite of the VLJ-repository at Olkiluoto, Johansson & Autio 1995 4) No values for tonalite were available, so the value for granite is applied here

4.7.2 Blasting properties

The main rock types at Olkiluoto have similar strength properties but there are differ­ences in their mineral compositions and textures which can affect their blasting proper­ties. The most significant differences in this regard are the relatively high mica content in mica gneiss and tonalite and the locally well-developed schistosity in mica gneiss. The share of the mica gneiss that has a well-developed schistosity is about 20 %.

When blasting in a strongly schistose rock and if the direction of the tunnel is close to the strike of the schistosity, the loosening of the rock at the tunnel profile takes place preferentially along the plane of the schistosity. This may cause overbreak to occur, resulting in roughness to the tunnel profile. Mica-rich zones may need greater charging than normal.

In general the rock types of Olkiluoto can be considered as easy or normal to blast and they were, therefore, usually placed into the normal class of constructability. However, the strongly schistose parts of the mica gneiss (about 20% of the total) were classified as demanding in cases when the direction of the tunnel is close to the strike of the schistosity.

94

4.7.3 Crushing properties

The main parameters affecting to the crushing properties of a rock are the orientation of minerals, its strength and its stiffness. With a normal 2 - 3 stage crushing process the amount of fine material (below 0.063 mm diameter) will be approximately 4 to 8 % of the total. Approximately 10 % of fines is required in a backfill aggregate and this neces­sitates a fourth crushing stage with a fine crusher or with a special mill (Tolppanen 1998).

The rock types at Olkiluoto are suitable for aggregates for use in backfill material and it is possible to achieve a level of 6 - 8 % of fines with a normal crushing process for mica gneiss, tonalite and granite/pegmatite. Aggregate particles from gneissic rocks can be elongated, but that can be avoided by splitting with an extra cone crusher.

The rock types at Olkiluoto are mostly easy or normal to crush and they are, therefore, placed into the normal class of constructability. The strongly schistose parts (20 %) of the mica gneiss are, however, classified as demanding.

4.7.4 Requirement for rock support

The requirement for rock support in a rock mass depends mainly on the extent of fracturing and weathering of the rock, on the hydrogeological conditions and on the in situ stresses. In this report the rock support requirements were estimated on the basis of the Q value (Figure 4.7-1) and on the hydrogeological conditions. The Q value is deter- . mined by the level and nature of the fracturing and weathering, the in situ stresses and, to a lesser extent, by the rock's hydrogeological properties. In addition to the Q value, attention was also paid to the rock's hydrogeological properties, so that structures which had been placed into the very demanding class, on the basis of their hydrogeological properties, were classified at least into the demanding class of constructability with re­gard to their support requirements, because groundwater ingress may complicate rock support significantly. The determination of the Q value is discussed in more detail in Section 4.8.

The requirements for rock support in the depth intervals of 0 - 200 m, 200 - 400 m, 400- 600 m and> 600 m were estimated on the basis of the Q values in Table 4.7-2. The span of the tunnel was presumed to be 6 m and the ESR (the excavation support ratio) was given a value of 1.0. Thus the estimate for rock support determined using these values is relevant for the central tunnel of the repository (Figure 1-1), but it may be little too conservative for the deposition tunnels. The requirement for rock support has been estimated separately for the arch and walls of a tunnel. The estimate of the walls was based on Qw ("wall quality") which depends on the Q value as follows (Barton et al. 1974):

Qw = 5 · Q, when Q > 10 Qw = 2.5 · Q, when 0.1 < Q ~ 10 Qw = 1.0 · Q, when Q ~ 0.1

E

.:

m "i

0 1: 0 0..

V)

G F

Exceptionally Extremely poor poor

95

c B A

Ex c. good

100 ~~~~~~Effi~=q~~~~~~~~~~$ff~ 20 50

20 0:: en w

10

5

2

0.001 0.004 0.01 0.04 0 .1

REINFORCEMENT CATEGORIES :

1) Unsupported

2) Spot bolting

3) Systematic bolting

4) Systematic bolting, land un reinforced shotcrete, 4-10 cm)

0

+-t-H+HI---t-+++++++1 11 ,...;

0::

7 ~

-l---'-4--7<+--l><-t--+++H--"---+___,...9-+-H+H 5 .2

0.4 1.0 4 10 40 100 400 1000

Rock mass quality Q

5) Fibre reinforced shotcrete and bolting, 5-9 cm

6) Fibre reinforced shotcrete and bolting, 9-12 cm

7) Fibre reinforced shotcrete and bolting, 12-15 cm

8) Fibre reinforced shotcrete, 15- cm, reinforced ribs of shotcrete and bolting

9) Cast concrete lining

E

.:

Figure 4. 7-1. Determination of rock support on the basis of Q value and the span of an underground excavation (Grimstad & Barton 1993).

The support requirements for tunnel walls was determined as shown in Figure 4. 7-1 using the Qw value in place of Q.

On the basis of the Q values determined, systematic bolting will be sufficient to provide support of the tunnel arch in all the rock types at Olkiluoto up to a depth of 400 m. Over the depth interval of 400 - 600 m systematic bolting combined with thin shotcrete will normally provide sufficient support. At greater depths temporary support and systematic bolting with a thick fibre-reinforced shotcrete are expected to be required.

All the rock types at Olkiluoto to a depth of 600 m were placed into the normal class of constructability (Q > 1). Since the geometric mean of the Q value for mica gneiss is close to the limit of the demanding class for the depth interval of 400 - 600 m, it is ap­parent that below about 500 m depth mica gneiss is likely to lie in the demanding class. The same conclusion can also be drawn for tonalite and for amphibolite/metadiabase. Below a depth of 600 m all the rock types at Olkiluoto were placed in the demanding class of constructability.

96

Table 4. 7-2. The requirement for rock support at the tunnel arch and walls of the repository depending on lithology and depth. The interpolated estimates are in italics. MGN = mica gneiss, GRIPG = granitelpegmatite, TON = tonalite, AFBIMDB = amphi­bol ite/metadiabase.

Rock type/ Support

Requirement for rock support (Q value) at different depth ranges

MGN

arch

walls

GRIPG

arch

walls

TON

arch

walls

AFB/MDB

arch

walls

Legend: Dark green Light green Yellow Light red

0-200 m 200-400 m 400-600 m >600 m

Sb 1.8 + scsf 60 mm (1.3) sb 1.5 + scsf 100 mm (0.24)

sb 2. 0 + se 40 mm sb 1.6 + scsf90 mm

sb 2.1 +se 40 mm (3.9) sb 1.6 + scsf90 mm (0.49)

sb 2.0 sb 1.8 + scsf60 mm

sb 1. 7 + sesj70 mm sb 1.4 + scsf 120 mm (0.14)

sb 2.0 + se 50 mm sb 1.5 + scsf 100 mm

sb 1.8 + sesf60 mm sb 1.5 + scsf 100 mm (0.25)

sb 2.1 + se 40 mm sb 1.6 + scsf80 mm

---} no support needed ---} systematic bolting (sb) and bolt spacing in metres ---} thin shotcrete with or without steel fibres (scsf or se) and its thickness ---} temporary support + systematic bolting with thick fibre-reinforced shotcrete and its

thickness

The requirement for rock support within the R-structures was examined (Table 4.7-3) with the help of Q values, and by investigating the geometric average of Q (Qgeomean) and the weakest 4 m long intersection of an R-structure by a borehole (Q4m). All the structures that were intersected in the boreholes down to a depth of 600 m were placed into the normal or demanding class of constructability. Six structures have been intersected at depths of more than 600 m. The structures R1, R10, R13 and R21 were classified according to the Q value as demanding, R15 and one unmodelled structure intersection (RX) were classified as very demanding. According to the Q4m values the structures R 10 and R21 were classified as very demanding. The structures R 1, R 11, R12, R19, R20 and R24 (shown in red in Table 4.7-3) were classified as demanding for hydrogeological reasons, even though they would have been classified as normal on the basis of their Q values.

97

Table 4. 7-3. The requirement for rock support of the R-structures and their constructa­bility as a function of depth according to Q value. RX refer to unmodelled structure intersections. The red structure symbols are those referred to in the text.

Depth/Class, Rock Normal Demanding Very support demanding

0-200 m

Qgeomean RX, R9, R11 , R12, R19, R1 R10 R24, R26

Q4m RX, R9, R10, R11 , R1 , R12, R24 R19, R26

200-400 m

Qgeomean RX, R1 , R2, R9, R14, R17, R20

Q4m RX, R1 , R2, R17, R9 R20

400-600 m

Qgeomean RX, R10, R13, R17, R20, R21 , R30

Q4m RX, R1 0, R17, R20, R21 , R30

>600m

Qgeomean R1 , R10, R13, R21 RX, R15

Q4m R13 R10, R21

Legend: ~ systematic bolting ~ thin shotcrete with or without steel fibres

Light green Yellow Light red Dark red

~ temporary support+ systematic bolting and thick fibre-reinforced shotcrete ~ temporary support + systematic bolting and thick fibre-reinforced shotcrete with rein­

forced ribs of shotcrete or cast concrete lining

98

4.8 NGI classification {Q value)

4.8.1 Determination of the Q value

The Q value of the NGI classification system was determined for the bedrock of the Olkiluoto investigation site to enable a comparison to be made of the quality of the rock mass. It is determined using six rock variables as follows (Barton et al. 1974; Grimstad & Barton 1993):

where

RQD = Rock Quality Designation (range 10- 100) = Joint set number (range 0.5- 20) = Joint roughness number (range 0.5 - 4) = Joint alteration number (range 0.75 - 20) = Joint water reduction factor (range 0.05- 1) = Stress Reduction Factor (range 0.5 - 400).

The Q value can vary between the range of 0.001- 1000. It is usually determined by collecting data during the mapping of tunnels or outcrops. In this work, however, the Q value was determined for each cored metre of the investigation boreholes. Since the de­termination of Q from drill cores always contains an element of subjective judgement which depends on the interpreter, the definition of the parameters is described in detail below.

The data used for the NGI classification consists of the drilling reports for boreholes KR1- KR10, surface mapping data, hydraulic conductivity measurements, strength and stress measurements and the bedrock model. The fracture database for Olkiluoto and the petrology reports were not used as source material, because they did not cover all the boreholes.

An RQD value is normally defined in the drilling reports. In regions of core loss, which was not common, the RQD value was determined on the basis of the results from the bore hole-TV image or the electrical dipmeter probe. Where the RQD value was esti­mated to be< 10 %, it was given a value of 10 %.

The joint set number In was determined according to Table 4.8-1 based on the surface mapping of the investigation site. It was given a constant value of 9, because on average three main fracture directions have been observed in the area. The determination of In for each metre of core would have given too favourable an impression of fracturing, because the subvertical boreholes on the site underestimate the extent of vertical frac­turing. In addition, one metre of core is not sufficient to evaluate fracturing at the scale of the repository tunnels, where spans are typically 3.3- 6 m, and even more than 10 m at the tunnel intersections.

99

Table 4.8-1. Determination of joint set number (In) based on the fracturing (adapted from Barton et al. 197 4 ).

Number of joint sets ~ Jn A Massive, no or few joints 0.5- 1

I B One joint set 2

c One joint set+ random joints i 3 I D Two joint sets i 4

E Two joint sets + random joints I 6 i

F Three joint sets ! 9

G Three joint sets + random joints I 12

H Four or more joint sets I 15

J Crushed rock I 20 I

The joint roughness number lr was defined according to Table 4.8-2. The large scale roughness was estimated using the shape parameter of fracture surfaces (irregular, curved, planar) and the small scale roughness was estimated on the basis of surface roughness descriptions (rough, smooth, slickensided). These have been reported sepa­rate! y for each fracture in the drilling reports.

If no fractures were observed within a metre of core, 1r was given a value of 3. The highest possible values of 1r, 4 and 5, which are given to stepped and discontinuous fractures, were not used, because those fractures cannot be detected from core samples or boreholes. For this reason the parameter 1r can give too conservative a value in places. In cases when the shape parameter and surface roughness description of frac­tures were not defined in the drilling reports, fractures were presumed to be irregular (with respect to their large scale roughness) and smooth (with respect to their small scale roughness), and thus 1r was given a value of 2. If it was only the small scale roughness that was undefined, the fracture was presumed to be smooth.

The joint alteration number la was determined according to Table 4.8-3. Fractures be­longing to classes c.3 and c.4 were not observed.

When calculating the Q value, the fracture with the smallest 1/Ja ratio (and conse­quently with the smallest Q value) was chosen to represent each metre of a borehole. Often in the drilling reports only the colour of the fracture had been determined, which means that the fracture filling or coating had been detected but the filling had not been specified. In that case la was given a value of 2 which is approximately the average of the possible range of values for a fracture with rock-wall contact (Table 4.8-3). The 1/Ja ratio gives an approximation of the shear strength of a fracture (Grimstad & Barton 1993) and therefore the function arctan(J/1a) can be regarded as the "friction angle" of fracture (Barton et al. 1974).

100

Table 4.8-2. Determination of joint roughness number (lr)from core samples.

Roughness parameter of fracture Large scale roughness (dm- m)

irregular, curved planar

Small scale rough,senrl-rough 3 1.5 roughness (mm- cm) smooth 2 1.0

slickensided 1.5 0.5

No rock-wall contact, roughness does not affect (filling > 2 mm)

1 1

Table 4.8-3. Determination of joint alteration number (la) from core samples (based on Barton et al. 1974). Ri (degree of fracturing) and Rp (degree of weathering) refer to the Finnish Engineering Geological Rock Classification System used in the drilling reports.

fi)R(.)~l(S'Wall~(.)ntact .·••·•···· ........• ·.•··••.· ...... Ja a.l -Coalesced fracture surfaces or tight, hard, impermeable filling (epidote, feldspar, 0.75

tourmaline)

- Unfractured rock 1---+------------------------·----~----·-·--·--·-·--·····-· ··-·-··-·---····--····--·

a.2 -Unaltered fracture walls, surface staining only 1.0

a.3 - Slightly altered fracture walls, non-softening mineral coatings/fillings, sandy 2.0 particles or disintegrated clay-free rock (carbonate, pyrite, rust)

- Colour recorded, but the filling was not specified

- Filling exists but is not specified

- Slickensided fracture, coating or filling is not identified

- Rock is weathered (R~ ~ :Q_ ____ ··-----·---·---·-----·--------···--·---·----·-······-·- -·--·-··-·---·-···-·-· a.4 -Sandy filling without clay 3.0 ·---t----- --·--------···-·--·-------·--·---·--···--······-··-- ·-·-·······-·-·-·········-··-a.S -Softening or low friction clay mineral coating, filling thickness~ 2 mm (clay, 4.0

mica, chlorite, kaolin, talc, graphite)

- Filling consists of solid particles and clay ...

b).Rock,.'\'Vallcontactafter $100 jrun sbear b.l - Clay mineral filling > 2 - 5 mm 8.0

c) No rock .. wall contact after><lOOntm. shear ··. ..

c.l - Clay mineral filling > 5 mm 8

c.2 - Crushed rock (RiiV) 8 r---4--------------------------------------------------------+---·----

c.J -Zones of clay or of disintegrated rock with swelling clay 8- 12 1---+-------·-·---------------------------------··---··-··----·-··-··-

c.4 - Thick continuous zones with swelling clay 13 - 20

The joint water reduction factor lw was determined based on difference flow measure­ments according to Table 4.8-4. If the measured hydraulic conductivity (KMoye) was < 1E-08 m/s, Iw was given a value of 1 and, if it were higher, it was given a value of 0.66. In the latter case it was assumed that rock mass would always be pre-grouted to achieve a value of K ~ 1E-8 m/s, in order to improve its constructability.

101

Table 4.8-4. Determination of joint water reduction factor ( lw) based on groundwater inflow (modified from LrjJset 1997).

Groundwater conditions Jw A Dry excavation or minor inflow (locally < 5 1/min) 1.0

B Medium inflow or pressure, occasional outwash of fracture 0.66 fillings

c Large inflow or high pressure in competent rock with unfilled 0.5 fractures

D Large inflow or high pressure, considerable outwash of fracture 0.33 fillings

E Exceptionally high inflow or water pressure at blasting, decaying 0.1-0.2 with time

F Exceptionally high inflow or water pressure continuing without 0.05-0.1 noticeable decay

In determining Iw, the results of hydraulic conductivity measurements using a 2 m packer interval were normally used. In some tight borehole sections the results of 30.8 m packer intervals were used because other data were unavailable. In borehole KR5 only 6.8 and 30.8 m and in KR6 5 - 30 m packer intervals were used.

In the upper sections of boreholes KR5 - KR8 (at most a 70 m length of borehole) the parameter Iw was given a value of 0.66, because hydraulic conductivity measurements were absent. If the results were absent only from a few metres of a borehole, adjacent values were applied instead. Where this situation occurred within a fracture zone, Iw was given a value of 0.66. No measurements were available from borehole KR10 over the depth interval of 0- 300 m and, in this borehole, Iw was given a value of 1 in the intact rock and 0.66 in the R-structures.

The stress reduction factor SRF was determined differently in intact rock and in R­structures consisting of fractured or crushed rock. In intact rock the SRF was deter­mined separately for each rock type based on the ratio of their compressive strengths (Table 4.8-5) and values of the maximum horizontal stress (instead of the maximum principal stress) according to Figure 4.8-1. The maximum horizontal stress was calcu­lated with the following equations (Figure 4.5-1 ):

crH = 0.041Z + 2.67 MPa (depth< 300 m) 4.8-1

crH = 0.056Z- 1.98 MPa (depth> 300 m) 4.8-2

where Z is the vertical depth from the ground surface.

In R-structures the SRF was determined both according to Table 4.8-6 and according to the method used for intact rock. In calculating the Q value the SFR value used was the one which gave the smaller value for Q.

102

Table 4.8-5. The strength values of rock types used in calculating the SRF.

Rock type Compressive strength (MPa)

Mica gneiss Granite/pegmatite Tonalite Amphibolite/metadiabase

100

I

110

130

95

100

7 SRF=-150x+5Q( I

80

SRF 60

40

20

0

200

If /

SRF=-23.25) lt-119.75/

SRF=1 SRF=-0.5x+6 y

10 5 3

Compressive strenght I Maximum principal stress

Figure 4.8-1. Dependence of SRF on the strength/stress ratio.

2

Table 4.8-6. Determination of the SRF in structures. Ri (degree of fracturing) refers to the Finnish Engineering Geological Rock Classification System that has been used in the drilling reports.

Description of structure/Stress reduction factor SRF

Intact rock or fractured rock (Rill) 1

Intact, hydraulically-conductive rock_ ..-.....,............~~ ............... -~ ............... -~,,....~~

Fracture zone (Rilll) or crushed rock (RiiV), vertical 5

depth from bedrock surface < 50 m

Fracture zone (Rilll) or crushed rock (RiiV), vertical 2.5

depth from bedrock surface > 50 m

I

103

4.8.2 Rock quality according to Q value

The variation of Q value as a function of depth is presented for every borehole in Fig­ures 4.8-2 - 4.8-5. The Q value graphs displayed in these figures are 4 m moving aver­ages which describe the average rock quality over about one excavation round. The following features can be seen in the graphs:

1. The Q value varies rapidly with an amplitude of about 0.5 - 1, caused mainly by variations in RQD, Ir and I a.

2. The SRF increases as the strength/stress ratio becomes smaller with an increase in the vertical depth (Z). This can be seen as changes of slope in the trendline of Q graphs, which mirror the changes of slope shown in Figure 4.8-1. In mica gneiss the changes of slope occur at depths of 210 m and 430 m and corresponding changes take place at depths of 260 m and 500 m in granite/pegmatite, 170 m and 370 m in tonalite and 180 m and 390 m in amphibolite/metadiabase.

3. There are minima in the Q graphs that differ noticeably from the general trend. They are usually related to intersections of fractured or crushed rock at that depth (i.e. R­structures).

4. The influence of rock type on the SRF can be seen as changes in magnitude of 0.5 - 1 in the trendlines of Q value, as there are only minor differences in strength between the different rock types.

The distribution of Q value for intact rock in each borehole and for different depth intervals (expressed as the vertical depth from the ground surface) are presented in Figures 4.8-6 - 4.8-8. In the depth interval 0 - 200 m the average rock quality varies between classes B and C (for the definition of these classes refer to Table 3.1-3). The best quality rock was found in borehole KR4 (Q = 24), where only minor fracturing is present, and the lowest quality (Q = 6) in borehole KR6, because of abundant fracturing and a small J/Ja ratio. In the depth interval 200- 400 m the average rock quality also varies between classes B and C. The best quality rock is observed in borehole KR 10 (Q = 11) and the worst in bore hole KR2 (Q = 6). In the depth interval 400 - 600 m the average rock quality varies between classes D and E. The best quality rock is found in borehole KR5 (Q = 2.7) and the worst in borehole KR2 (Q = 0.9). At depths > 600 m the average rock quality lies in class E. The strong decrease of Q value with depth is due mainly to the increase of in situ stress, which strongly influences the value of Q. Some rock properties, such as the hydraulic conductivity of fractures and the fracture fre­quency, may even become more favourable with increasing depth from a constructa­bility point of view.

Legend:

Length of the hole

Om

-100 m

-200 m

-300 m

-400

-500 m

-600 m

-700 m

-800 m

-900 m

-1000 m

-1100 m

Granite/Pegmatite

TonalitefTonalite gneiss

Amphibolite

Mica gneiss

Structure

18.10.1999 HM/Saanio & Riekkola Oy

R

•

1001.1 m

104

R1 R71

Figure 4.8-2. Variation of Q value in boreholes KRJ, KR5 and KR7 at Olkiluoto.

Legend:

Length of the hole

Om

-100 m

-200 m

-300 m

-400 m

-500 m

-600 m

-700 m

-800 m

-900 m

-1000 m

Granite/Pegmatite

Tonalite/Tonalite gneiss

Amphibolite

Mica gneiss

Structure

18.10.1999 HM/Saanio & Riekkola Oy

R

105

1051.9m

Figure 4.8-3. Variation of Q value in boreholes KR2 and KR6 at Olkiluoto.

Legend:

Length of the hole

-1000 m

Granite/Pegmatite

Tonalite/Tonalite gneiss

Amphibolite

Mica gneiss

Structure

18.10.1999 HM/Saanio & Riekkola Oy

106

R

Figure 4.8-4. Variation of Q value in boreholes KR4, KR8 and KRJO at Olkiluoto.

Legend:

Length of the hole

Om

-100 m

-200 m

-300 m

-400 m

-500 m

502.0 m

-600 m

-700 m

-800 m

-900 m

-1000 m

Granite/Pegmatite

Tonalite!Tonalite gneiss

Amphibolite

Mica gneiss

Structure

18.10.1999 HM/Saanio & Riekkola Oy

R

107

R

Om

-100 m

-200 m

-300 m

-400 m

-500 m

-600 m

601.3m

-700 m

-800 m

-900 m

-1000 m

Figure 4.8-5. Variation of Q value in boreholes KR3 and KR9 at Olkiluoto.

~

~·

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...J ~ -~ -~ S<i • • ooo 08£~ -~ ui lL N

Figure 4.8-8. Distribution of Q value within intact rock, depth interval400- 600 m.

111

The distribution of Q values for intact rock of each rock type over different depth inter­vals (determined as vertical depth and not including any contribution from R -structures) is presented in Figure 4.8-9. Over the depth interval 0- 200 m the average rock quality for all the rock types is class B, however tonalite differs from the other rock types as its Q value is greater. Over the depth interval 200-400 m the average rock quality varies from class B to C, with only mica gneiss being noticeable on the basis of its slightly smaller Q value. Over the depth interval 400- 600 m the bedrock consists mostly of mica gneiss and granite/pegmatite, and both are placed into class D, with mica gneiss having a smaller Q value due to its lower strength. Amphibolite and tonalite occur only occasionally in this depth interval. At depths > 600 m all the rock types were placed in class E, with granite/pegmatite representing the best rock quality and tonalite the worst. At these depths the low value of Q and the differences in quality of the rock types are mainly due to the relatively high stresses and differences in rock strengths.

The distribution of Q values in intact rock according to block division and depth inter­vals (vertical depths) is shown in Figure 4.8-10. Over the depth interval 0- 200 m investigation boreholes intersect blocks 2, 4, 5 and 9 and the average rock quality varies from class B to class C, being weakest in block 9. Over the depth interval 200 - 400 m the boreholes intersect block 1 in addition to the above mentioned blocks and the average rock quality varies from class B and C, being best in block 4 and worst in block 1. The differences between those blocks are, however, minor. Over the depth interval 400- 600 m the investigation boreholes intersect blocks 1 - 6 and 8. The average rock quality varies from class C toE, being best in block 1 and worst in block 8. The differ­ence is due to the relatively short borehole intersection lengths in this depth interval. The intersections in block 1 are in the interval 400 - 412 m and those in block 8 between 581 - 600 m, where the stresses are considerably higher. At depths> 600 m the investi­gation boreholes intersect blocks 5 - 8 and 10 and the average rock quality lies in class E, being best in block 5 and worst in block 10.

The Q values of all the intersections of R-structures (35 in total) are shown in Table 4.8-7, where they are divided according to the R-structures (16 in total) and the depth intervals of 0 - 200 m, 200 - 400 m, 400 - 600 m and > 600 m. Fewer than half of the structures have been intersected only once and the rest of the structures have been intersected 2- 4 times. 39% of the structure intersections are situated in the depth interval 0- 200 m, 26% in the depth interval 200- 400 m, 21 % in the depth interval 400- 600 m and 13% at depths > 600 m. The Q values of the unmodelled structure intersections (RX) are also given in Table 4.8-7.

In Table 4.8-7 the average (geometrical mean) Q value of structures is shown. In addi­tion, Q4m, which is the geometrical mean of the 4 m long intersection of a structure with the lowest quality rock, has been determined. It provides an approximation of the rock quality for the worst excavation round. Q4m was calculated only where intersections were > 4 m. The Q4m is significantly weaker than the average rock quality only in structure R24 (in the depth interval 0 - 200 m) and in structure R21 at depths > 600 m.

Mica gneiss

0-200 m

Q = 12.97 (1343 m)

200-400 m

1 3

Q=8.56 (1128 m)

400-600 m

>600m

7 2

Q = 1.27 (845 m)

Q =0.24 (704 m)

0.001-0.01

Granite/ pegmatite

Q = 12.89 (248 m)

Q= 10.20 {209 m)

Q=3.92

(192 m)

Q = 0.49 (247 m)

112

Tonalite

Q= 20.30 (121 m)

14

Q = 10.07 (197 m)

Q= 0.14 (52 m)

0. 0 1-0.1 D 0.1-1 D 1-4 D 4-10

18

Amphibolite/ metadiabase

Q= 10.86 (14 m)

11

Q = 10.11 (9 m)

Q=0.25 (16 m)

10-40 • 40-100

Figure 4.8-9. Distribution ofQ value(%) within intact rock according to rock type over the depth intervals 0 - 200 m, 200 - 400 m, 400 - 600 m and > 600 m.

Block 1 Block 2 Block4 BlockS Block 6 Block 7 Block 8 Block 9

0-200m

2

~e 29

22

45~ 39

I · ~

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2

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24 64

I '---"""

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400-600 m

~ 10 2

e5 t) 2~ 9~3 19

54 75 46 66 84

Q = 5.20 (14 m) I I Q = 2.49 (58 m) Q = 4.06 (4 m) Q = 1.44 (827 m) Q = 2.44 (80 m) Q = 0.42 (32 m) Block 10

>600m

e)75 (5) (98 t5 CD 0.01-0.1 D 0.1-1 D 1-4

I I 68 72 71

57 10-40 • 40- 100

Q = 0.59 (150 m) Q = 0.17 (151 m) Q = 0.18 (72 m) Q = 0.36 (476 m) Q = 0.12 (160 m)

Figure 4.8-10. Distribution(%) ofQ values according to the block division in intact rock in the depth intervals ofO- 200 m, 200- 400 m, 400 - 600 and > 600 m.

"'--' "'--' w

114

Table 4.8-7. Q values (geometric averages) of the intersections of the R-structures in the bedrock model of Olkiluoto for depth intervals 0 - 200 m, 200 - 400 m, 400 - 600 m and > 600 m. RX refers to intersections of unmade/led structures.

Structure Rl R2 R9 RlO Rll R12 R13 R14 Rl5

0-200 m Number of intersections 2 1 Length (m) 4 5 23 6 10

Q value 0.89 1.66 6.06 2.19 1.45

Q4m 0.89 1.18 2.76 1.53 0.50

200-400 m Number of intersections 1 2 1 Length (m) 5 18 19 2

Q value 1.15 3.70 1.67 1.86

Q4m 1.04 1.21 0.69

400- 600m Number of intersections 1 Length (m) 28

Q value 0.44

Q4m 0.19

>600m Number of intersections Length (m) 2

Q value

Q4m

Structure R17 Rl9 R20 R21 R24 R26 R30 RX

0-200 m Number of intersections 3 2 4 5 Length (m) 11 39 14 76 Q value 2.40 2.86 3.47 8.14

Q4m 1.95 0.43 1.53 3.01

200-400 m Number of intersections 2 3 8 Length (m) 24 51 52 Q value 1.89 2.42 3.53

Q4m 1.48 1.09 2.58

400-600 m Number of intersections 3 6

Length (m) 21 15 32 5 18

Q value 0.51 0.87 0.17 0.25 0.18

Q4m 0.12 0.58 0.06 0.24 0.21

>600m Number of intersections Length (m)

Q value

Q4m

0.001-0.01 0.01-0.1 D 0.1-1 D 1-4 04-10 10-40 • 40-100

115

The intersection lengths shown in Table 4.8-7 are summaries of all the intersections of a structure within a certain depth interval. Where an intersection extends over two adja­cent depth intervals, it is shown as two separate structure intersections in the table (structures R9, R10 and R13).

Over the depth interval 0 - 200 m the quality of the poorest rock varies from class D to E, being worst in structures R1, R12 and R24. In the depth interval 200-400 m the quality of the poorest rock varies from class D to E, being worst in structure R9. Over the depth interval 400- 600 m the corresponding class range is E- F, with the weakest structures being R13 and R21. At depths> 600 m the quality of the poorest rock lies in classes F and G, being worst in structure R 15.

On the basis of the average Q value of intact rock, all the rock types and blocks at Olki­luoto over the depth interval 0 - 500 m, were placed into the normal class of constructa­bility. The change from normal to demanding takes place over the depth interval of 400-600 m.

Over the depth interval 0-200 m R-structures R9, R10, R11, R19 and R26, as well as the unmodelled structure intersections (RX), were placed in the normal class of con­structability according to Q4m, and the structures R 1, R 12 and R24 in the demanding class. Over the depth interval 200-400 m structures R1, R2, R14, R17, R20 and the unmodelled structure intersections (RX) were placed in the normal class and R9 in the demanding class. Over the depth interval 400- 600 m structures R10, R13, R17, R20, R21, R30 and the unmodelled structure intersections (RX), and at depths > 600 m structures R 1 and R 13 were all placed into the demanding class of constructability. At depths > 600 m structure R 15, parts of R 10 and R21, and one RX structure intersection were classified as very demanding.

117

5 DISCUSSION AND CONCLUSIONS

The constructability of the bedrock at the Olkiluoto site was classified on the basis of lithological properties, fracture properties, hydrogeological properties, structural rock type, in situ stress, groundwater chemistry, rock engineering properties and Q value. The classification of the bedrock was studied with reference to five spatial variables: rock type, intact rock/R-stucture (whether the rock mass in question belongs to intact rock or to the R-structures of the bedrock model), depth, block number and borehole number. Rock quality was found to depend mainly on the first three of these variables, depending on the classification property, and only slightly on the remaining two vari­ables (Table 5-1). Block-specific and especially borehole-specific dependencies were, therefore, examined to a lesser extent than those of the others.

The classification of the constructability was mainly based on rock samples and investi­gations made in boreholes but, in addition, the results of surface mapping were used. The bedrock model that has been used as one source of material is based on both surface and borehole studies. The current investigation site, which covers the majority of the area of the footprint of the proposed location of the future repository, contains 10 cored boreholes over an area of about 2 km2

. The majority of the borehole data lies in the depth range of 0- 600 m and at greater depths borehole data are available only from boreholes KR1, KR2 and KR4. According to the present basic repository concept, which consists of 1400 canisters, the area required for the location of the deposition tunnels is 0.4 km2 whereas the block model has an area of 3.5 km2 at a depth of 500 m. Most investigation data lie within blocks 4 and 5 which are adjacent. The area of block 5 at 500 m depth is about 2 km2 and data from the other blocks at this depth are few or nonexistent.

The number of borehole data associated with the R -structures of the bedrock model varies significantly depending on the structure. Seven R-structures are intersected by 3- 4 boreholes, nine R-structures by 1 to 2 boreholes and fourteen modelled structures are not intersected by any boreholes, so they have been left outside the classification. There are 19 unmodelled structure intersections (RX) in total, which is a substantial proportion of all the structure intersections by boreholes, implying that there are possi­ble deficiencies in the bedrock model. In the probable depth interval for the repository of 400 - 600 m there are nine intersections of the modelled R -structures and six of the unmodelled (RX) structures.

There is uncertainty in much of the source material used in this classification of the bed­rock, especially in relation to the representativeness of the borehole data and the as­sumptions regarding the development of the bedrock and block models, in particular the number and properties of the R-structures. In turn, this uncertainty limits the extent to which reliance can be placed on the results of the classification. Additional investiga­tions in the area of the proposed repository and over the depth range of interest are re­quired to obtain more information on the bedrock characteristics in order to make deci­sions regarding the optimal placement of the repository.

The constructability of the bedrock at Olkiluoto is summarised in Table 5-2 based on the properties of the bedrock. It is also discussed separately below in more detail.

118

Table 5-1. Dependence of rock mass classification parameters on five spatial variables. liS = intact rock/structure. X = dependence is examined, (X) = dependence is estimated. Colours: red = strong dependence, yellow = moderate dependence, green = weak dependence.

Parameter/Spatial variable Rock Depth liS Block Hole type

Lithological properties: Mineral composition X

Degree of foliation X

Grain size X - - -· -· -

Degree of weathering (X) (X) X X -- ---

Strength and deformation X

properties Thermal properties X

Fracture properties: Number of fracture sets X

- - - -- ---

Fracture frequency X X X X --

Fracture trace length X (X) (X) (X) - -

Frictional properties X X ---- 1- ---

Fracture witdh X X X (X)

Hydrogeological properties: -

Hydraulic conductivity X X X (X) ! -

Water ingress and grouting (X) X

properties Structural rock type:

i - - - 1- - 1- ~

Intact, fractured and crushed rock X X X X - - 1- - 1- -

Hydraulically-conductive rock X X

State of stress: -

Principal stresses X

Strength/stress ratio X

Groundwater chemistry: pH X

Sulphate content X

Free carbon dioxide X

Ammonium content X

Magnesium content X -

Chloride content X X -

Radon content X

Rock engineering properties: Drillability X

Blasting properties X

Crushing properties X

Requirement for rock support X X X

NGI classification: -- - --- --

-~- 1-- -Q value X X X X X

Table 5-2. Constructability of the bedrock at Olkiluoto based on the rock properties. RX refers to unmodelled borehole intersections of structures. The bedrock is placed into the three constructability classes of normal, demanding and very demanding with respect to each property.

Property /Constructability class Normal I Demanding Very demanding

Lithological properties:

a) mineral composition all rock types lie in this class

b) degree of schistosity generally applicable to all rock 20% of mica gneiss lies in this class types

c) grain size all rock types lie in this class

d) degree of weathering intact rock lies in this class parts of structures RX, R9, R15, R17, R19, parts of structures R19, R20 R20, R21

e) strength properties granite/pegmatite, amphibolite/ some mica gneiss and tonalite metadiabase and some mica gneiss and tonalite

I f) thermal properties all rock types lie in this class

Fracture properties: I a) number of fracture directions all rock types lie in this class

I b) fracture frequency intact rock

structures generally parts of structures R9, R 17, R2I parts of structures R I2, R24

c) fracture length intact rock and structures generally

1

intact rock and structures locally

d) frictional properties all rock types generally I all rock types locally

structures RX, RI, Rll, RI4, R15, I parts of structures R2, R9, RIO, RI2, Rl3, parts of structures RI2, RI3, R24 RI9, R26, R30 RI7, R20, R2I, R24

e) fracture width intact rock and structures generally I intact rock and especially locally within

•

---~-----~~---------~-----~---~-----------------~- ~

J~tructures (usually at shallow depths) -~ -----~------~---~--~--------

........

........ \0

Property/Constructability class Normal

Hydrogeological properties intact rock generally

structures R2, R9, RlO, R13, R14, R15, R17, R30

Structural rock type intact rock generally

structures R2, RIO, R13, R14, R15, R30

State of stress intact rock generally and mica gneiss

(Strength/stress ratio) if depth < 340 m

Groundwater chemistry pH, sulphate, free carbon dioxide, ammonium, magnesium and radon

Rock engineering properties:

a) drillability all rock types

b) blasting properties all rock types generally

c) crushing properties I all rock types generally

d) rock support:

I intact rock generally if depth 1) intact rock <500m

2) structures 0- 200 m structures RX, R9, RlO, R26

3) structures 200-400 m I structures R2, RIO, R14, R17

4) structures 400-600 m

5) structures > 600 m

--·--·-·---·· ~6-~---L-- --·-----------

Demanding

intact rock locally (at 100 m intervals at 500 m depth)

structure R26

intact rock locally (hydraulically-conductive rock at 100 m intervals at 500 m depth)

parts of structures RX, R9, R 17, R26

mica gneiss if depth> 340 m and< 520 m

chloride in the depth range 0 - 400 m

20 % of mica gneiss

20 % of mica gneiss

intact rock generally if depth> 500 m

structures Rl, Rll, R12, R19, R24

structures Rl, R9, R20

structures RlO, R13, R17, R20, R21, R30

structures R 1, R 13 and parts of R 10 and R21

'-----·-----~---- ---------------------~-------··

Very demanding

structures Rl, Rll, Rl2, R19, R20, R21, R24

parts of structures Rl, Rll, Rl2, R19, R20, R21, R24

mica gneiss if depth > 520 m

chloride if depth > 400 m

structures RX, R 15 and parts of RlO and R21

-·

1

........ N 0

Property/Constructability class Normal Demanding Very demanding I I

Q value:

1) intact rock intact rock generally at< 500 m intact rock generally at > 500 m

2) structures 0 - 200 m structures RX, R9, RIO, RII, RI9, structures RI, R I2, R24 R26

3) structures 200 - 400 m structures RX, RI, R2, RI4, R17, structure R9 R20

4) structures 400- 600 m structures RIO, R13, R17, R20, R21, R30

5) structures > 600 m structures RI, R I3 and partly RI 0 and R21 structures RX, R I5 and parts of RIO and R2I

......... N .........

122

With regard to lithological properties, the intact rock at Olkiluoto, which most com­monly consists of mica gneiss and granite/pegmatite, is usually placed into the normal class of constructability. The degree of schistosity and strength properties of mica gneiss resulted in it being placed partly in the demanding class. Some of the R-struc­tures were classified partly as demanding or very demanding on the basis of their degree of weathering.

Based on its fracture properties, the intact rock at Olkiluoto was mainly placed into the normal class of constructability. Due to natural variations in rock quality, it is antici­pated that rock of the demanding class may occur locally and, in practice, this means that heavier rock support than normal may locally be required. With regard to the fric­tional properties of fractures the majority of the R-structures were classified as de­manding and three structures (R12, R13, R24) partly as very demanding, which means in practice that temporary support could be required to avoid the risk of local failures. With regard to fracture length, rock belonging to the very demanding class of construc­tability is present in structures R12 and R24.

The hydro geological properties of the intact rock were usually classified as normal from the constructability point of view. Hydraulically-conductive fractures or fracture zones which are likely to require grouting are found on average at 100 m intervals at the planned repository depth of about 500 m. The transmissivity (T) of several R-structures was estimated to be so great that they were classified as very demanding.

With regard to the structural rock type the intact rock of Olkiluoto was mainly classified as normal in terms of its constructability. However, rock classified as demanding, mainly hydraulically-conductive rock, is found locally. Six of the R-structures were classified as normal, four as demanding and seven as very demanding with regard to the structural rock type. The very demanding class includes the hydraulically-conductive structures R1, R11, R12, R19, R20, R21 and R24. Structure R19 is present only at shallow depth and thus does not affect the location of the deposition tunnels, however, it could influence the location of the shafts. Only a small amount of crushed rock is pres­ent in the borehole intersections of structures and none are, therefore, classified as being very demanding on the basis of their structural rock type. When evaluating the con­structability of the R-structures, it should be remembered that each structure is only ever intersected by a small number of boreholes and occasionally by only one.

With regard to the state of stress (and the strength/stress ratio) the main rock type at 01-kiluoto, mica gneiss, was placed into the normal or demanding class of constructability at depths of less than about 500 m. At greater depths rock bursts may occur locally and the rock was classified as very demanding. The other rock types at Olkiluoto are ex­pected to behave in a similar manner on the basis of their strength values. The normal variation in strength and stress measurements and the method used for analysis means that the range of depth for the normal class of constructability may be greater than that indicated. The orientation of the deposition tunnels parallel to the maximum horizontal stress will improve the stability of the tunnels. However, this will not significantly im­prove the stability of the disposal holes and any vertical shafts as they will always re­main perpendicular to the maximum horizontal stress.

123

On the basis of groundwater chemistry the bedrock at Olkiluoto was classified as nor­mal over the range of depth investigated with regard to all groundwater parameters ex­cept the chloride content. With regard to this parameter the bedrock was classified as demanding in the depth range of 0 - 400 m and very demanding at greater depths. The high chloride content of ground water means from the constructability point of view that better corrosion protection than normal will be required for example for rock support and underground pipework.

In terms of rock engineering properties, all the rock types of Olkiluoto were normally placed into the normal class of constructability. Mica gneiss was partly classified as de­manding, however, with regard to its blasting and crushing properties. With regard to its blasting properties this is a valid conclusion only where the direction of a tunnel is approximately parallel to the schistosity. The evaluation of the requirement for rock support was based on the determination of the Q value. Systematic bolting of tunnel arch to depths of 400 m is considered sufficient. In the depth range of 400 - 600 m, besides systematic bolting, shotcrete is likely to be required and, at greater depths, temporary support with systematic bolting and thick fibre-reinforced shotcrete are required. The R-structures were usually classified as normal or demanding in the depth range of 0 - 400 m. In the depth range of 400 - 600 m structures were classified as demanding and at greater depths as demanding or very demanding.

On the basis of the Q value, the intact rock at Olkiluoto to a depth of 500 m was usually placed in the normal class of constructability. At depths in excess of this it was classi­fied as demanding. The R-structures were usually classified as normal or demanding in the depth range of 0-400 m. At greater depths they were classified mainly as demand­ing or very demanding. Structure R15, one unmodelled structure intersection (RX) and parts of structures R 10 and R21 were classified as very demanding, at depths greater than 600 m. Structure R15 is, however, present only at depths greater than those consid­ered for repository construction and will not affect the constructability of the deposition tunnels. It should be noted that there are only limited or even no borehole data available from several R-structures. For example in the depth range of 400- 600 m there are borehole data from only six modelled R-structures. This lack of data limits the extent to which any of these R-structures can be properly classified.

The R-structures, which were classified as being very demanding in terms of their con­structability and which should be avoided when locating deposition tunnels, have been marked in red in Figures 5-l and 5-2. Structure RlO has been marked in red, even though it has been classified as very demanding only at depths greater than 600 m. Structure R19, which was also classified as very demanding, cannot be seen in Figures 5-1 and 5-2 as it lies horizontally at a depth of 100 m and between the cross sections.

...... 01 1\) ~ 01 0 0

3

OLKILUOTO Horizontal section at 500 m depth (z=-500 m)

Structural model 3.0 FintacUJLU25.09.98/rc/olki/ s.up-500-sr-raklrak_3.0/PS

Geo model 3.0 FintacUJLi/29.1 0.98/rc/olki21 s.sec-z500-sr-geo/geo_3.0/PS

Coordinate system: Finnish Coordinate System, zone 1 (Projection: Gauss-Kruger)

Scale: 1: 20 000

26.4.2000 HM/Saanio & Riekkola Oy

~ 1\) 01 01 0 0

3

LEGEND:

D Tonaliteffonalite gneiss

D Granite/Pegmatite

• Metadiabase

D Mica gneiss

Veined gneiss

• Amphibolite

124

~ ~ ...... 01

1\) 1\) 1\) m m ...... 0 01 0 0 0 0 0 0 0

3 3 3

Structures in the bedrock model:

Location of borehole Structures to be avoided .6.. t 500 d th by deposition tunnels KR

1 a m ep

Other structures

Vertical projection of base of .6.. borehole on to 500 m

(z=~~ m) horizontal section (for boreholes 400-500m)

Area covered by the engineering rock mass classification

Figure 5-l. Location of the very demanding class structures (marked in red), horizontal section at a depth of 500 m.

01 N ~ 01 0 0

0)

""" CO VJ CJ1 0 0

0

R3

-1 000

0 200 400

OLKILUOTO

Cross section A-A

Structural model 3.01

0)

""" CO VJ 0 0 0

Cross section B-B

Structural model 3.0

FintacUJLi/27.10.98/rc/olki2/ FintacUJLi/28.10.98/rc/olki21 s.sec-x6792500-sr-rak/rak _ 3.0/PS s.sec-y1525500-sr -rak/rak _ 3.0/PS

Geo model 3.0 Geo model 3.0

FintacUJLi/27 .1 0.98/rc/olki21 FintacUJLi/28.1 0.98/rc/olki21 s.sec-x6792500-sr -geo/geo _ 3.0/PS s .sec-y1525500-sr -geo/geo _ 3.0/PS

125

A-A .... .... 01 01 N N 0> 0> 0 01 0 0 0 0

B-B 0) 0)

""" """ CO CO N N CJ1 0 0 0 0 0

'1. Core drilled borehole

Granite/Pegmatite Structures

D Tonalite!Tonalite gneiss in the bedrock model:

• Amphibolite

D Mica gneiss I. Structures to be avoide

by deposition tunnels

26.4.2000 HM/Saanio & Riekkola Oy § Veined gneiss I Other structures

Figure 5-2. Location of the very demanding class structures (marked in red), vertical cross sections A-A and B-B.

126

The following conclusions can be made regarding the constructability of the bedrock based on the rock mass classification:

1. In the depth range of 300 - 700 m, no bedrock properties were discovered that would prevent the construction of a final disposal repository using conventional hard rock engineering methods.

2. The intact rock, which usually consists of migmatized mica gneiss, has been placed mainly into the normal class of constructability in the upper part of this depth range and the R-structures into the normal or demanding class. In the lower part of this depth range the constructability of mica gneiss is considered to be demanding and the constructability of the R-structures to be demanding or very demanding, due to the increase of in situ stress with depth.

3. The requirement for rock support will increase with increase in depth. On the basis of the Q values, it is estimated that the tunnels can be constructed using systematic rock bolting and thin shotcrete in the upper part of the depth range. In the lower part of the depth range the requirement for rock support increases so that temporary support, in addition to systematic rock bolting and thick fibre-reinforced shotcrete, is likely to be required. Due to the variation in the classification parameters, the geotechnical be­haviour of mica gneiss and correspondingly the requirement for rock support may differ locally from that estimated on the basis of the average Q value.

4. The structures Rl, RIO, Rll, R12, R19, R20, R21 and R24, which have all been clas­sified as very demanding, are considered effectively to determine the possible loca­tions of the deposition tunnels. Of these, RlO is classified as very demanding only at a depth of more than 600 m; Rll is present only over the depth range of 0-400 m and R19 is present only at shallow depth. Most of these structures have been classi­fied as very demanding on the basis of their hydrogeological properties. Structures R 10 and R21 are significant with regard to their rock engineering properties, and R21 is also hydrogeologically significant.

5. The chloride content of the ground water increases significantly with depth and, based on this factor, the constructability of the bedrock was classified as demanding to a depth of 400 m and as very demanding at greater depths. In practice, this means that better corrosion protection than normal will be required for underground compo­nents.

6. There is uncertainty in much of the source material used in this classification of the bedrock, especially in relation to the representativeness of the borehole data and the assumptions regarding the development of the bedrock and block models, in par­ticular the number and properties of the R -structures. In turn, this uncertainty limits the extent to which reliance can be placed on the results of the classification. Addi­tional investigations in the area of the proposed repository and over the depth range of interest are required to obtain more information on the bedrock characteristics in order to make decisions regarding the optimal placement of the repository.

127

6 SUMMARY

Olkiluoto in Eurajoki is being investigated as a possible site for the final disposal of spent nuclear fuel from the Finnish nuclear power plants. The selection of the depth, placement and layout of the repository is affected by the constructability of the bedrock. The constructability, in turn, is influenced by several properties of the host rock, such as its lithology, the extent of fracturing, its hydro geological properties and rock engineer­ing characteristics and also by the magnitude and orientation of the in situ stresses and the chemistry of the groundwater. The constructability of the bedrock can be evaluated by the application of a rock classification system in which the properties of the host rock are assessed against common rock engineering judgements associated with under­ground construction. These judgements are based partly on measurements of the in situ stress and the properties of the bedrock determined from rock samples, but an important aspect is also the practical experience gained from underground excavation in general.

The aim of the engineering rock mass classification was to determine suitable bedrock volumes for the construction of the repository and has used data from the site charac­terisation programme carried out at Olkiluoto. The classification specifies three catego­ries of constructability - normal, demanding and very demanding. In addition, rock mass quality has also been classified according to the empirical NGI system (Q value) to en­able a comparison to be made.

The constructability was defined as normal with regard to a classification parameter, if tunnelling can be carried out by conventional hard rock tunnelling methods, using stan­dard materials and assuming a normal level of operational efficiency, whilst allowing for the high quality of construction required for the deposition tunnels. The constructa­bility was defined as demanding where more sophisticated and expensive construction methods and materials would be required. The rate of tunnelling would in this situation be considerably reduced, compared with the rate associated with rocks in the normal class, or considerable effort would have to be placed on aspects of operational safety. The constructability was defined as very demanding where much more sophisticated and expensive construction methods and materials would be needed. In this case the rate of tunnelling would be very much lower or even more effort would have to be placed on operational safety.

The classification was based on the results of the Olkiluoto site investigations, which consist of surface and borehole investigations and the development of a 3D bedrock model. The investigation area of approximately 2 km2 contains 10 boreholes, the major­ity to a depth of 600 m. Data are available from greater depths than this, but only from three boreholes which extend to depths of 850 - 1000 m.

The classification of the bedrock was studied with reference to five spatial variables: rock type, intact rock/R-stucture (whether the rock mass in question belongs to intact rock or to the R-structures of the bedrock model), depth, block number and borehole number. Rock quality was found to depend mainly on the first three of these variables, depending on the classification property, and only slightly on the remaining two vari­ables (Table 5-l). Block-specific and especially borehole-specific dependencies were examined to a lesser extent than those of the others.

128

With regard to lithological properties, the intact rock at Olkiluoto, which most com­monly consists of mica gneiss and granite/pegmatite, is usually placed into the normal class of constructability. The degree of schistosity and strength properties of mica gneiss resulted in it being placed partly in the demanding class. Some of the R-struc­tures were classified partly as demanding or very demanding on the basis of their degree of weathering.

Based on its fracture properties, the intact rock at Olkiluoto was mainly placed into the normal class of constructability. Due to natural variations in rock quality, it is antici­pated that rock of the demanding class may occur locally. With regard to the frictional properties of fractures the majority of the R-structures were classified as demanding and a few structures partly as very demanding, which means in practice that temporary sup­port could be required to avoid the risk of local rock failure. With regard to fracture density, rock belonging to the very demanding class of constructability is present in only a few structures.

The hydro geological properties of the intact rock were usually classified as normal from the constructability point of view. Hydraulically-conductive fractures or fracture zones which probably need grouting are found on average at 100 m intervals at the planned repository depth of about 500 m. The transmissivity (T) of several R-structures was esti­mated to be so great that they were classified as very demanding.

With regard to the structural rock type the intact rock of Olkiluoto was mainly classified as normal in terms of its constructability. However, rock classified as demanding, mainly hydraulically-conductive rock, is found locally. Six of the R-structures were classified as normal, four as demanding and seven as very demanding with regard to the structural rock type. The very demanding class includes the hydraulically-conductive structures R1, R11, R12, R19, R20, R21 and R24. Structure R19 is present only at shallow depth and thus does not affect the location of the deposition tunnels; however, it could influence the location of the shafts. Only a small amount of crushed rock is pres­ent in the borehole intersections of structures and none are, therefore, classified as being very demanding on the basis of their structural rock type. When evaluating the con­structability of the R-structures, it should be remembered that each structure is only ever intersected by a small number of boreholes and occasionally by only one.

With regard to the state of stress (and the strength/stress ratio) the main rock type of 01-kiluoto, mica gneiss, was classified as normal or demanding at depths of less than about 500 m. At greater depths rock bursts may occur locally and the rock was classified as very demanding. The other rock types at Olkiluoto are expected to behave in a similar manner on the basis of their strength values.

On the basis of groundwater chemistry the bedrock at Olkiluoto was classified as nor­mal over the range of depth investigated with regard to all groundwater parameters ex­cept the chloride content. With regard to this parameter the bedrock was classified as demanding in the depth range of 0-400 m and very demanding at greater depths.

129

In terms of rock engineering properties, all the rock types of Olkiluoto were normally placed into the normal class of constructability. Mica gneiss was partly classified as demanding, however, with regard to its blasting and crushing properties. With regard to its blasting properties this is a valid conclusion only where the direction of a tunnel is approximately parallel to the schistosity. The evaluation of the requirement for rock support was based on the determination of the Q value. Systematic bolting of tunnel arch to depths of 400 m is considered sufficient. In the depth range of 400 - 600 m, besides systematic bolting, shotcrete is likely to be required and, at greater depths, temporary support with systematic bolting and thick fibre-reinforced shotcrete are required. The R-structures were usually classified as normal or demanding in the depth range of 0 - 400 m. In the depth range of 400 - 600 m structures were classified as demanding and at greater depths as demanding or very demanding.

On the basis of the Q value, the intact rock at Olkiluoto to a depth of 500 m was usually placed in the normal class of constructability. At depths in excess of this it was classi­fied as demanding. The R-structures were usually classified as normal or demanding in the depth range of 0-400 m. At greater depths they were classified mainly as demand­ing or very demanding. Structure R15, one unmodelled structure intersection (RX) and parts of structures R 10 and R21 were classified as very demanding, at depths greater than 600 m. Structure R15 is, however, present only at depths greater than those consid­ered for repository construction and will not affect the constructability of the deposition tunnels.

The following conclusions were made regarding the constructability of the bedrock based on the rock mass classification:

1. In the depth range of 300-700 m, no bedrock properties were discovered that would prevent the construction of a final disposal repository using conventional hard rock engineering methods.

2. The intact rock, which usually consists of migmatized mica gneiss, has been placed mainly into the normal class of constructability in the upper part of this depth range and the R-structures into the normal or demanding class. In the lower part of this depth range the constructability of mica gneiss is considered to be demanding and the constructability of the R-structures to be demanding or very demanding, due to the increase of in situ stress with depth.

3. The requirement for rock support will increase with increase in depth. On the basis of the Q values, it is estimated that the tunnels can be constructed using systematic rock bolting and thin shotcrete in the upper part of the depth range. In the lower part of the depth range the requirement for rock support increases so that temporary support, in addition to systematic rock bolting and thick fibre-reinforced shotcrete, is likely to be required. Due to the variation in the classification parameters, the geotechnical be­haviour of mica gneiss and correspondingly the requirement for rock support may differ locally from that estimated on the basis of the average Q value.

I30

4. The structures RI, RIO, RII, RI2, RI9, R20, R2I and R24, which have all been clas­sified as very demanding, are considered effectively to determine the possible loca­tions of the deposition tunnels. Of these, RIO is classified as very demanding only at a depth of more than 600 m; Rll is present only over the depth range of 0 - 400 m and R19 is present only at shallow depth. Most of these structures have been classi­fied as very demanding on the basis of their hydrogeological properties. Structures RlO and R21 are significant with regard to their rock engineering properties, and R21 is also hydrogeologically significant.

5. The chloride content of the ground water increases significantly with depth and, based on this factor, the constructability of the bedrock was classified as demanding to a depth of 400 m and as very demanding at greater depths. In practice, this means that better corrosion protection than normal will be required for underground compo­nents.

6. There is uncertainty in much of the source material used in this classification of the bedrock, especially in relation to the representativeness of the borehole data and the assumptions regarding the development of the bedrock and block models, in par­ticular the number and properties of the R-structures. In turn, this uncertainty limits the extent to which reliance can be placed on the results of the classification. Addi­tional investigations in the area of the proposed repository and over the depth range of interest are required to obtain more information on the bedrock characteristics in order to make decisions regarding the optimal placement of the repository.

131

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Rautio, T. 1995c. Extension drilling of deep borehole OL-KR2 at Olkiluoto in Eurajoki 1995 (in Finnish with an English abstract). Helsinki, Finland: Teollisuuden Voima Oy. 132 p. Work Report PATU-95-62.

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137

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138

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139

APPENDIX 1: Distribution of frictional properties of fractures in structures given as an average length per one coring intersection and percentually (given in brackets)

Structure Total Inter- Joint roughness number Jr (m (%))

code

RX

R1

R2

R9

RlO

R11

R12

R13

R14

R15

R17

R19

R20

R21

R24

R26

R30

Total (m) Intersect. RX x.x (x.x)

x.x

(m) sect. Jr= 0.5 Jr= 1

148 19 0.6 (8.1) 1.5

12 3 1.0 (25.0) 0.0

18 1 l 1.0 (5.6) 1.0

24 2 0.0 (0.0) 1.5

60 3 1.7 (8.3) 3.3

6 1 1.0 (16.7) 1.0

10 1 2.0 (20.0) 1.0

10 1 5.0 (50.0) 2.0

2 1 0.0 (0.0) 1.0

2 1 0.0 (0.0) 1.0

45 3 0.7 (4.4) 2.3

11 3 0.3 (9.1) 0.3

66 4 1.0 (6.1) 2.5

70 4 1.3 (7.1) 6.8

39 2 3.5 (17.9) 1.5

14 4 0.3 (7.1) 0.5

5 1 0.0 (0.0) 1.0

= Total length of coring intersections = Number of coring intersections = Unidentified structure intersections

(18.9)

(0.0)

(5.6)

(12.5)

(16.7)

(16.7)

(10.0)

(20.0)

(50.0)

(50.0)

(15.6)

(9.1)

(15.2)

(38.6)

(7.7)

(14.3)

(20.0)

Jr= 1.5 Jr=2

1.8 (23.6) 0.8 (10.8)

1.7 (41.7) 1.0 (25.0)

5.0 (27.8) 6.0 (33.3)

2.5 (20.8) 2.5 (20.8)

3.3 (16.7) 3.7 (18.3)

4.0 (66.7) 0.0 (0.0)

3.0 (30.0) 1.0 (10.0)

2.0 (20.0) 1.0 (IO.Q)

0.0 (0.0) 0.0 (0.0)

0.0 (0.0) 1.0 (50.0)

4.3 (28.9) 1.7 (11.1)

1.3 (36.4) 0.3 (9.1)

4.8 (28.8) 1.3 (7.6)

0.8 (4.3) 3.0 (17.1)

10.5 (53.8) 0.5 (2.6)

1.5 (42.9) 0.3 (7.1)

4.0 (80.0) 0.0 (0.0)

Proportion of parameter given as average length per one intersection = Proportion of parameter given as average percentual share per one intersection

Jr= 3

3.0 (38.5)

0.3 (8.3)

5.0 (27.8)

5.5 (45.8)

8.0 (40.0)

0.0 (0.0)

3.0 (30.0)

0.0 (0.0)

1.0 (50.0)

0.0 (0.0)

6.0 (40.0)

1.3 (36.4)

7.0 (42.4)

5.8 (32.9)

3.5 (17.9)

1.0 (28.6)

0.0 (0.0)

= Altogether at least 3.0 m coring intersection of demanding or extremely demanding rock/structure

I

I

140

Structure Total Inter-~

code (m) sect. Ja = 0.75 Ja= 10

Joint alteration nu1nber la (nl (%))

RX

Rl

R2

R9

RlO

Rll

R12

R13

R14

RlS

R17

R19

R20

R21

R24

R26

R30

Total (m) Intersect. RX x.x (x.x)

x.x

148

12

18

24

60

6

10

10

2

2

45

11

66

70

39

14

5

19

3

2

3

1

1

3

3

4

4

2

4

0.8 (10.8) 0.4 (5.4) 4.6 (58.8) 0.6 (7.4) 1.2 (15.5) 0.2 (2.0) 0.0 (0.0)

I o.o co.o) !

I o.o (0.0)

I o.o co.o) I 1 2.0 oom !

I 0.0 (0.0)

0.0 (0.0)

I o.o (0.0)

i 0.0 (0.0)

I o.o (0.0)

11.0 (6.7)

I 0.0 (0.0)

0.8

1 0.5

11.0 I o.3

! 0.0 I

(4.5)

(2.9)

(5.1)

(7.1)

(0.0)

0.0 (0.0) 2.0 (50.0) 0.0 (0.0) 2.0 (50.0) 0.0 (0.0) 0.0 (0.0)

2.0 (11.1) 10.0 (55.6) 1.0 (5.6) 5.0 (27.8) 0.0 (0.0) 0.0 (0.0)

0.0 (0.0) 5.5 (45.8) 0.0 (0.0) 6.5 (54.2) 0.0 (0.0) 0.0 (0.0)

0.3 (1.7) 15.7 (78.3) 0.0 (0.0) 1.7 (8.3) 0.3 (1.7) 0.0 (0.0)

0.0 (0.0) 6.0(100.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0)

0.0 (0.0) 5.0 (50.0) 0.0 (0.0) 5.0 (50.0) 0.0 (0.0) 0.0 (0.0)

1.0 (10.0) 6.0 (60.0) 0.0 (0.0) 3.0 (30.0) 0.0 (0.0) 0.0 (0.0)

0.0 (0.0) 2.0(100.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0)

0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 2.0(100.0) 0.0 (0.0)

0.3 (2.2) 8.3 (55.6) 0.3 (2.2) 4.0 (26.7) 1.0 (6.7) 0.0 (0.0)

0.3 (9.1) 2.0 (54.5) 0.3 (9.1) 1.0 (27.3) 0.0 (0.0) 0.0 (0.0)

1.0 (6.1) 9.0 (54.4) 1.3 (7.6) 2.8 (16.7) 1.8 (10.6) 0.0 (0.0)

0.3 (1.4) 13.0 (74.3) 0.8 (4.3) 0.5 (2.9) 2.5 (14.3) 0.0 (0.0)

1.5 (7.7) 15.0 (76.9) 0.5 (2.6) 1.0 (5.1) 0.5 (2.6) 0.0 (0.0)

0.0 (0.0) 3.0 (85.7) 0.0 (0.0) 0.3 (7.1) 0.0 (0.0) 0.0 (0.0)

0.0 (0.0) 5.0(100.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0)

Total length of coring intersections = Number of coring intersections = Unidentified structure intersections = Proportion of parameter given as average length per one intersection = Proportion of parameter given as average percentual share per one intersection = Altogether at least 3.0 m coring intersection of demanding or extremely demanding

rock/structure

141

Structure Total Inter-~ Friction an:gle lj> (m(%)}

code (m) sect. 1 <1> = 0-15 <1> = 16-30 <1> = 31-45 <1> = 46-60 <1> = 61-75 <1> = 76-90

RX

R1

R2

R9

R10

R11

R12

R13

R14

R15

R17

R19

R20

R21

R24

R26

R30

Total (m) Intersect. RX x.x (x.x)

x.x

148

12

18

24

60

6

10

10

2

2

45

11

66

70

39

14

5

19

3

2

3

1

1

3

3

4

4

2

4

·---0.9 (11.5) 1.5 (18.9) 2.7 (35.1) 1.7 (22.3) 0.1 (1.4) 0.8 (10.8)

1.0 (25.0) 1.0 (25.0) 2.0 (50.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0)

1.0 (5.6) 4.0 (22.2) 9.0 (50.0) 3.0 (16.7) 1.0 (5.6) 0.0 (0.0)

1.0 (8.3) 2.0 (16.7) 7.5 (62.5) 1.5 (12.5) 0.0 (0.0) 0.0 (0.0)

2.0 (10.0) 4.0 (20.0) 6.7 (33.3) 5.0 (25.0) 0.3 (1.7) 2.0 (10.0)

1.0 (16.7) 1.0 (16.7) 4.0 (66.7) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0)

2.0 (20.0) 1.0 (10.0) 7.0 (70.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0)

7.0 (70.0) 1.0 (10.0) 1.0 (10.0) 1.0 (10.0) 0.0 (0.0) 0.0 (0.0)

0.0 (0.0) 1.0 (50.0) 0.0 (0.0) 1.0 (50.0) 0.0 (0.0) 0.0 (0.0)

2.0 (100.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0)

1.7 (11.1) 3.0 (20.0) 6.3 (42.2) 3.0 (20.0) 0.0 (0.0) 1.0 (6.7)

0.3 (9.1) 0.7 (18.2) 2.0 (54.5) 0.3 (9.1) 0.3 (9.1) 0.0 (0.0)

2.3 (13.6) 4.5 (27.3) 3.8 (22.7) 4.5 (27.3) 0.8 (4.5) 0.8 (4.5)

3.5 (20.0) 5.8 (32.9) 3.5 (20.0) 4.3 (24.3) 0.0 (0.0) 0.5 (2.9)

4.0 (20.5) 1.5 (7.7) 9.0 (46.2) 3.5 (17.9) 0.5 (2.6) 1.0 (5.1)

0.3 (7.1) 0.5 (14.3) 2.0 (57.1) 0.5 (14.3) 0.0 (0.0) 0.3 (7.1)

0.0 (0.0) 1.0 (20.0) 4.0 (80.0) 0.0 (0.0) 0.0 (0.0) 0.0 (0.0)

= Total length of coring intersections = Number of coring intersections = Unidentified structure intersections = Proportion of parameter given as average length per one intersection = Proportion of parameter given as average percentual share per one intersection = Altogether at least 3.0 m coring intersection of demanding or extremely demanding

rock/ structure

142

APPENDIX 2: The measured hydraulic conductivities of the A-structures

Structure Bore- Bore hole z Vertical Max. Mean Hydraulically- K of the hydr.- Estimated number hole depth masl* depth hydraulic hydr.cond. conductive conductive of hydraulic.-

interval 0 =+0 m** conduc- (geom. borehole sections (K>lE-9) conductive tivity mean) features fractures

Rl KR1 847 ... 850 -781...-783 781...783 < 1E-IO

Rl KRS 405 .. .410 -350 ... -355 350 ... 355 2E-8 6l 405.2 .. .4I0.2 2E-8 6) 5-20

Rl KR6 216 ... 220 -162 ... -165 I62 ... 165 2E-7 4) 218.12 ... 219.9 2E-7 4

) 1 -5

R2 KRS 253 ... 27I -2I7 ... -233 2I7 ... 233 7E-7 4) 268.5 ... 270.63 7E-7 4) 5-10

R9C KR3 IS7 ... I62 -138 ... -I42 I38 ... I42 < IE-10 -R9A KR3 386 ... 397 -344 ... -354 344 ... 354 3,7E-08 I,3E-09 386.7 ... 388.7 2,06E-09 II

388.7 ... 390.7 3,70E-08 8 390.7 ... 392.7 2,09E-09 2 392.7 ... 394.7 I,S6E-09 7

R9B KRS 275 ... 283 -236 ... -243 236 ... 243 2E-7 5) 278.I9 ... 283.0 2E-7 5

) 5- 10 RlOA KRI SI4 ... 542 -477 ... -503 477 ... 503 I,26E-07 4,8E-10 522.9 ... 524.9 I,04E-08 3

525.0 .. .527.0 I,3E-07 6 533.0 ... 535.0 I,SE-08 2 537.0 ... 539.0 3,6E-08 10

RlOB KRI 764 ... 773 -706 ... -7I4 706 ... 7I4 3,3E-10 I,3E-10 -RlOC KR3 IIS ... I3I -99 ... -II4 99 ... II4 5,99E-07 2,3E-09 116.3 ... II8.3 2,0E-08 3

II8.3 ... I20.3 6,0E-07 3 I20.3 ... I22.3 I,9E-08 3 I26.3 ... I28.3 I,7E-09 9

RlOD KRS I20 ... I27 -99 ... -105 99 ... 105 3E-7 4) I23.2 ... I24.9 3E-7 4) 5- IS

Rll/R26 KRI 106...II2 -92 ... -98 92 ... 98 0,00000689 9,3E-08 I04.3 ... 106.3 3,94E-09 I I 06.3 ... 108.3 I,9SE-08 2 I08.3 ... I10.3 6,9E-06 4 II0.3 ... 112.3 1,4E-07 2

R12 KR6 126 ... 136 -94 ... -101 94 ... 101 2.4E-7 7) 126.9 .. .132.4 2.4E-7 7

) I -5 R13 KR1 636 ... 646 -590 ... -599 590 ... 599 < IE-10 R14 KR2 405 .. .407 -379 ... -38I 379 ... 381 < IE-10 -

R17A KR2 218-225 -201...-208 201...208 1,01E-08 7,6E-10 212.5 ... 214.5 1,0E-08 1-3 214.5 ... 216.5 S,OE-09 1- 5 2I6.5 ... 218.5 9,1E-09 I-9

R178 KR2 236 ... 250 -218 ... -23I 218 ... 231 0,00000176 1,3E-09 234.5 ... 236.5 1,4E-07 1-4 236.5 ... 238.5 1,8E-06 2-3

R17C KR4 503 ... 524 -478 ... -498 478 ... 498 2,42E-08 3,3E-10 508.2 ... 510.2 3,1E-09 7 510.2 ... SI2.2 2,4E-08 6 522.2 ... 524.2 I,6E-09 12

Rl7C KRIO 367 ... 370 -m ... -3~ ~57 ... 360 l,IE-09 3,3E-10 366.6 ... 368.6 1,1E-09 10-25

Additional information on fracture observations, other remarks

405.20-410.20 Rilll zone, number of fractures not defined

218.12-219.9 Riiii zone, number of fractures not defined

268.50-270.63 Rilll zone, number of fractures not defined

Mineralogy report: 1I open fractures Mineralogy report: 8 open fractures Mineralogy report: 2 open fractures Mineralogy report: 7 open fractures

278.I9-283.00 Riiii zone, number of fractures not defined Number of open fractures in the fracture database Number of <JIJen fractures in the fracture database Number of open fractures in the fracture database Number of open fractures in the fracture database

Mineralogy report: 3 open fractures Mineralogy report: 3 open fractures Mineralogy report: 3 open fractures Mineralogy report: 3 open fractures

I23.20-I24.90 Riiii zone, number of fractures not defined I weathered fracture (borehole-TV) 2 weathered fractures (borehole-TV) 4 open fractures (borehole-TV) 2 open fractures (borehole-TV)

126.19-129.45 Riiii zone, number of fractures not defined

TV: 1 fracture with calcite filling, no open fractures. Mineralogy report: 3 open fr. TV: 1 fr. with calcite filling and 2 weathered fr., no open fr. Min. report: 5 open fr. TV: several fr. with hematite and 1 calcite filling. Mineralogy report: 9 open fr. TV: no fractures. Mineralogy report: 4 open fractures TV: 2 open fractures. Mineralogy report: 3 open fractures Number of open fractures in the fracture database Number of open fractures in the fracture database Number of open fractures in the fracture database 25 open fractures in the fracture database

1--' .+;:... V-)

Structure Bore- Borehole z Vertical Max. Mean hole depth masl* depth hydraulic hydr.cond.

interval 0 =+0 m** conduc- (geom. tivity mean)

R19 KR4 80 ... 85 -69 ... -74 69 ... 74 5E-5 2l 2.8E-07 2

l

R19 KR7 82 ... 84 -67 ... -69 67 ... 69 < lE-10 R19 KR8 80 ... 84 -60 ... -63 60 ... 63 2,72E-05 1,4E-07

R20A KR4 310 ... 316 -292 ... -298 292 ... 298 1,31E-05 8,6E-09

R20B KR4 366 ... 371 -346 ... -351 346 ... 351 0,00000304 3,1E-08

R20C KR7 225 ... 240 -201...-215 201...215 7,1E-06 1,7E-07

R20D KR7 278 ... 289 -251...-261 251...261 2,6E-05 1,8E-07

R20E KR9 442 ... 447 -400 ... -405 400 .. .405 2,34E-07 S,SE-09

R20F KR9 471...481 -426 ... -435 426 . ..435 0,00000701 6,4E-10 R20B KRIO 326 ... 328 -316 ... -318 316 ... 318 S,9E-07 S,9E-07 R21 KRI 613 ... 618 -569 ... -573 569 ... 573 4,38E-07 7,SE-08

R21 KR2 597 ... 615 -560 ... -577 560 ... 577 1,7E-06 9,SE-10

R21 KR4 757 ... 795 -718 ... -753 718 ... 753 3,2E-10

R21 KR5 467 .. .476 -404 ... -412 404 .. .412 2E-7 4l

Hydraulically- K of the hydr.-conductive conductive

borehole sections (K>lE-9) features

79.4 ... 81.4 2.4E-8 2l

81.4 ... 83.4 5.6E-5 ll

83.4 ... 85.4 1.6E-8 2l

-77.3 ... 79.3 6,8E-07 79.3 ... 81.3 8,1E-08 81.3 ... 83.3 2,7E-05

305.8 ... 307.8 1,3E-06 311.8 ... 313.8 1,3E-05 313.8 ... 315.8 2,4E-08 364.9 ... 366.9 3,0E-06 367.9 ... 369.9 1,9E-08 369.9 ... 371.9 1,9E-09 222.0 ... 224.0 4,6E-07 224.0 ... 226.0 1,4E-06 226.0 ... 228.0 3,9E-06 228.0 ... 230.0 7,1E-06 234.0 ... 236.0 2,0E-07 236.0 ... 238.0 1,8E-08 238.0 ... 240.0 8,8E-06 240.0 ... 242.0 3,9E-06 278.0 ... 280.0 3,7E-07 280.0 ... 282.0 1,5E-05 284.0 ... 286.0 2,6E-OS 286.0 ... 288.0 2,6E-OS 442.9 ... 444.9 2,3E-07 444.9 ... 446.9 7,0E-09 472.9 .. .474.9 7,0E-06 326.5 ... 328.5 S,9E-07 611.1...613.1 4,1E-07 613.1...615.1 4,4E-07 615.1...617.1 1,66E-08 617.1...619.1 1,07E-08 599.1...601.1 1,7E-06 601.1...603.1 1,3E-07 613.1...615.1 3,0E-09

472.66 .. .475.50 2E-7 4l

Estimated number of hydraulic.-

conductive fractures

3

5

6

3 4,0 8 7 2 11 4 1 9 1

1-4 5- 10 5-10 1-3

5- 10 5 -10 5- 10 5- 10

3 5- 10 s- 10 s -10 3-6 5-10

s 3

10-30 s- 20

3 3 7 2

2- 10

Additional information on fracture observations, other remarks

TV: no fractures. Mineralogy report: 3 open fractures. Grouted

TV: 1 fr. with calcite filling. Mineralogy report: 5 open fr. and a fracture zone. Grouted

TV: 1 fracture with calcite filling. Mineralogy report: 6 open fractures. Grouted

Mineralogy report: 3 open fractures Mineralogy report: 4 open fractures Mineralogy report: 8 open fractures Number of open fractures in the fracture database Number of open fractures in the fracture database Number of open fractures in the fracture database Number of open fractures in the fracture database One filled fracture observed Number of open fractures in the fracture database Mineralogy report: 1 open fractures Mineralogy report: no open fractures, 4 filled fractures Sample disintegrated in the drilling process Sample disintegrated in the drilling process Mineralogy report: 3 filled fractures Sample disintegrated in the drilling process Min. report: 3 filled fr., conductivity possibly related to the fr. zone below (depth err.) Fracture zone Mineralogy report: several broken fractures Mineralogy report: 3 broken fractures Mineralogy report: several broken fractures Sample disintegrated in the drilling process Drilling report: IS filled fractures Drilling report: 9 filled fractures Drilling report: 1 S filled fractures Number of open fractures in the fracture database Number of open fractures in the fracture database Some 30 open fractures observed Some 20 open fractures observed Number of open fractures in the fracture database Number of open fractures in the fracture database Number of open fractures in the fracture database Number of open fractures in the fracture database

472.66-475.50 RiiV zone, number of fractures not defined

I

J

I

.......... +::-­+::--

Structure Bore- Borehole z Vertical Max. Mean Hydraulically- K of the hydr.- Estimated number Additional information on fracture observations, hole depth masl* depth hydraulic hydr.cond. conductive conductive of hydraulic.- other remarks

interval 0 =+0 m** conduc- (geom. borehole sections (K>lE-9) conductive tivity mean) features fractures

R24 KR8 105 .. .140 -83 ... -114 83 ... 114 1,62E-05 2,6E-08 103.4 ... 105.4 2,1E-08 4 Mineralogy report: 4 open fractures 105.4 ... 107.4 1,6E-05 4 Mineralogy report: 4 open fractures 109.4 .. .111.4 1,3E-06 3 Mineralogy report: 3 open fractures 111.4 ... 113.4 1,8E-08 4 Mineralogy report: 4 open fractures 113.4 .. .115.4 3,7E-06 3 Mineralogy report: 3 open fractures 115.4 ... 117.4 1,3E-08 3 Mineralogy report: 3 open fractures

R24 KR8 105 ... 140 -83 ... -114 83 ... 114 1,62E-05 2,6E-08 117.4- 119.4 3,77E-08 5 Mineralogy report: 5 open fractures 119.4 ... 121.4 2,32E-07 4-10 Mineralogy report: 4 open fractures+ fracture zone 120.55-122.48 121.4 ... 123.4 5,8E-07 1 -10 Mineralogy report: 1 open fractures + fracture zone 125.4 ... 127.4 2,4E-07 4 Mineralogy re_port: 4 open fractures 131.4 ... 133.4 3,33E-08 1 Mineralogy report: 1 open fractures 133.4 ... 135.4 5,07E-08 2 Mineralogy report: 2 open fractures 135.4 ... 137.4 4,03E-09 8 Mineralogy report: 8 open fractures 137.4 ... 139.4 6,91E-08 3- 10 Mineralogy report: 3 open fractures+ fracture zone 138.19-139.25 139.4 ... 141.4 3,29E-08 8 Mineralogy report: 8 open fractures

R24 KR9 147 ... 151 -131...-134 131...134 4,95E-06 1,3E-07 146.4 ... 148.4 4,95E-06 5-10 Drilling report: 15 filled fractures 148.4 ... 150.4 3,97E-06 5-10 Drilling report: 15 filled fractures

R26 KR2 73 ... 75 -62 ... -64 62 ... 64 3E-7 1> 1.4E-07 1

> 72.2 ... 74.2 2.3E-7 1> 3 Mineralogy report: 3 open fractures. Grouted

R30 KR9 545 ... 550 -492 ... -497 492 .. .497 1,6E-09 5,1E-10 547.0 .. .549.0 1,60E-09 5-10 Drilling report: 20 filled fractures

n K value of the grouted section has been multiplied by 100

l) K value of the grouted section has been multiplied by 10 3> 30 m HTU value

4> 2 m K value estimated from the 30 m HTU value, assuming that a narrow fracture zone (Rilll) is the hydr.-conductive feature

S) 7 m HTU value 6> 5 m K value estimated from the 30 m HTU value, assuming that a 5 m fracture zone (Rilll) is the only hydr.-conductive feature

7> based on conductivity measurements with a 5.5 m packer interval * depth level (metres above sea level) ** vertical depth (zero level is z = +0 m)

......... +:-. Ul.

LIST OF REPORTS 1 (2)

POSIV A REPORTS 2000, situation 6/2000

POSIV A 2000-01

POSIV A 2000-02

POSIV A 2000-03

POSIV A 2000-04

POSIV A 2000-05

POSIV A 2000-06

Interpretation of the Hastholmen in situ state of stress based on core damage observations Matti Hakala Gridpoint Finland Oy January 2000 ISBN 951-652-087-1

Rock mechanics stability at Olkiluoto, Hastholmen, Kivetty and Romuvaara Erik Johansson, Jari Rautakorpi Saanio & Riekkola Oy February 2000 ISBN 951-652-088-X

Sorption and desorption of cesium on rapakivi granite and its minerals Tuula Huitti, Martti Hakanen Laboratory of Radiochemistry Department of Chemistry University of Helsinki Antero Lindberg Geological Survey of Finland April2000 ISBN 951-652-089-8

Porewater salinity and the development of swelling pressure in bentonite-based buffer and backfill materials David A. Dixon Atomic Energy of Canada Limited June 2000 ISBN 951-652-090-1

In-situ failure test in the Research Tunnel at Olkiluoto forma Autio, Erik Johansson, Timo Kirkkomiiki Saanio & Riekkola Consulting Engineers Matti Hakala Gridpoint Finland Oy Esa Heikkilii Helsinki University of Technology Laboratory of Rock Engineering May2000 ISBN 951-652-091-X

Regional distribution of microbes in groundwater from Hastholmen, Kivetty, Olkiluoto and Romuvaara, Finland Shelley A. Haveman, Emma Larsdotter Nilsson, Karsten Pedersen Goteborg University, Sweden June 2000 ISBN 951-652-092-8

POSIV A 2000-07

POSIV A 2000-08

LIST OF REPORTS 2 (2)

Site scale groundwater flow in Olkiluoto - Complementary simulations J ari wfman VTTEnergy June 2000 ISBN 951-652-093-6

Engineering rock mass classification of the Olkiluoto investigation site Kari Aikiis (editor), Annika Hagros, Erik Johansson, Hanna Malmlund, Ursula Sieviinen, Pasi Tolppanen Saanio & Riekkola Consulting Engineers Henry Ahokas, Eero Heikkinen, Petri Jiiiiskeliiinen, Paula Ruotsalainen, Pauli Saksa Fintact Oy June 2000 ISBN 951-652-094-4