ShaftSinkingPracticesfor Mining

8/9/2019 ShaftSinkingPracticesfor Mining

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ShaftSinkingPracticesfor Mining

Chairmen: J.S. Redpath

C. Heever

].S. Redpath Ltd. North Bay Ont. Canada

Cyril Heever Partners Inc. Carletonville South Africa


2/22

Chapter

SHAFT SINKING AT NOSE ROCK

by

Mr. James O. Greenslade

PhillipsUranium Corporation

Vice Presidentof Mining & Milling

Crownpoint,New Mexico

Mr. Cherie Tilley

PhillipsUranium Corporation

DevelopmentManager


Mr. Gerald G. Griswold

HarrisonWestern Corporation

Vice Presidentof EngineeringServices

Denver, Colorado

Mr. Richard Reseigh

HarrisonWestern Corporation

Manager of Engineering& Administration


INTRODUCTION

The HarrisonWestern Corporation,a leadingDenver based mine

contractingand engineeringconcern,is presentlyengaged in

sinking two 1,006 m (3,300 ft) shafts for the PhillipsUranium

Corporationat their Nose Rock Project,approximately13 miles

northeastof the small communityof Crownpointin McKinleyCounty,

New Mexico. The Nose Rock Project is the first attempt by the

PhillipsUranium Corporationto tap the deep uranium reservesin

what has become known as the Grants Mineral Belt. (See Figure 1)

ProjectDescription

PhillipsUranium Corporations plan for the large 2700 metric

ton per day (2950 tons/day)mining facilitycalls for a series of

deep access and ventilationshafts ranging from 4.27 m (14 ft) to

5.49

m

(18

ft) in diameterto approximatedepths of 1,006m (3,300

ft). The initialpair of shafts consistsof one productionshaft and

one ventilationshaft separatedby a distanceof

91 m (300

ft).

The

interbedded layers of sedimentary sandstones and shales to be

penetrated by the shafts contain several major water producing

aquifers, the deepest being the mineralized zone called the Westwater

Canyon Member of the Morrison Formation.

955


3/22

956

1981 RETC PROCEEDINGSVOLUME 2

FIGURE 1.

PROJECT SITE


4/22


957

A series of temporaryand permanentwater pumping stationsis

planned. Generally,the temporarystationsare located above

major aquifers to facilitatewater removalwhile sinking through

the aquiferand the permanentstationsconstitutewhat, in the

final mode, will be the mine dewateringsystem. In addition,

PhillipsUranium Corporationhas installedand is maintaininga

system of depressurizationwells that temporarilypump the major aqui-

fers and considerablyreduce the water inflows durinq shaft construc-

tion,

The major aquifers are alao chemicallygroutedprior to sinking.

Site work for the project was initiatedin the fall of 1976. Full

scale shaft sinking commencedin November of 1977 on the 4.88 m (I6

ft) diameterventilationshaft and on the 5.49 m (18 ft) production.

shaft by another contractor.

HarrisonWestern Corporationbegan work

on the project on November 4,

1979 with the productionshaft at a

depth of 633 m (2,076 ft) and the ventilationshaft at a depth of 474

m (1,554 ft).

This paper will address only the portion of shaft

sinking completedby HarrisonWestern.

Geology and Hydrology

The Nose Rock Project is located on the Chaco Slope in the

southernextreme of the San Juan Basin in northwestNew Mexico.

The southernSan Juan Basin is generallybound by the Defiance

Uplift to the west, the Zuni Uplift to the south and the

NacimientoUplift to the east.

The Grants MineralBelt occupies

most of the southernportion of the San Juan Basin and this pro-

ject is located on the northernextreme of the Grants Mineral

Belt. The San Juan Basin is comprised of sedimentary rock of

continental, marginal-marine and marine origin, that dip northward

from the Zuni Uplift and Chaco Slope into the interiorof the San

Juan Basin.

(SeeFigure 2)

Major Formations The major geologic formationsto be penetrated

range from mudstoneand shales to ailtstonesand sandstones.

The

sandstonesare highly productiveaquiferswhich, under static

conditions,would flow artesian.

Water temperaturesin the aqui-

fers are high and thereforeare a force to be dealt with. Temper-

atures range from 18C (65F)in the upper aquifersto 48C

(118F)in the lower. The mudstonesare generallybentonitic.

(SeeFigure 2)

GALLUP SANDSTONE: The Gallup Sandstoneis the first major

regressivewedge in the San Juan Basin of the Cretaceus era and

at this project is about 35 m

(115

ft) thick.

It is medium

grainedand prior to depressuriation carrieda hydrostaticwater

3

pressureof over 72.5 kg per cm (1,031psi) whi~h is artesian.

Compressivestr ngthranges from 334.7 kg per cm (4,760psi) to

421.8 kg per cm (6,OOOpsi).

Water temperatureis approximately

30c (860F).


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958

1981

RETC PROCEEDINGSVOLUME 2

C.EOLCC,C ~.w.. o. COLUMN

T-

*

M, N, F.,

MLLATO TONG.,

OF . . .

MA.cos

MC,t.lcos

812

26s

w, ,W.R w...

w..,.

,

,6 )

WCI),.OUJCTION SHAFT No,, v,r4T,.AT,ON SHAFT

,_L_EPT.

.m. . .

= :

..s.O ,

.....

.

m,,

, ,...,,

i

FIGURE 2. SHAFTSVERTICAL CROSS SECTION


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MANCOS SHALE:

The Mancos Shale comprisesthe bulk of marine

depositsin the San Juan Basin and representsdepositionin

deeper, quieter water in offshoreareas where energy levelswere

lower and finer elasticscould settle out. At Nose Rock, the

Mancos Shale is roughly 207 m (680 f~) thick. Compressive

st engths range from 188.4 kg per cm

5

(2,680 psi) to 400.7 kg per

cm (5,700psi).

It is not water bearing.

DAKOTA SANDSTONE: The Dakota Sandstoneand its corresponding

Twowellsmember is approximately98 m (322 ft) thick at Nose

Rock. The main body of the Dakota Sandstoneis a fine grained

sandstonewith the so calledTwowells sandstonetongue actually

being a siltstone. Prior to depressurization,wate~ ;: ;;yI)) ta

was under a hydrostaticpressure of 108.1kg per cm ,

also artesian.

2

Compressivest engthsrange from 386.okg per cm

(5,490psi) to 562.4 kg per cm (8,OOOPsi). Water temperatureis

approximately43C (109F).

BRUSHY BASIN SHALE: The Brushy Basin Member is the upper-most

member of the MorrisonFormationwhich marks the approximate

boundry between the Cretaceus and Jurassic eras. Locally, it is

composedof a sequenceof fine grained sandstones,siltstonesand

mudstoneswhich grade into one another,althoughdisconformities

are sometimesdistinguishable.

The mudstonesand siltstones

constitutethe greater part of the section. Overall, it is Q4 m

(143 ft) thick and some of the sandstonesare wa er bearing.

3

Compressivestr ngths range from 456.3 kg per cm (6,49o psi) to

5

954.8 kgpercm (13,580Psi).

WESTWATER CANYON MEMBER: The WestwaterCanyon Member of the

MorrisonFormationwas depositedin a continentalenvironment

during the Jurassic era and is the ore bearing sandstonefor the

Nose Rock Project. It is actually comprisedof three submembers

called Upper, Middle and Lower.

The WestwaterCanyon Member is a

classic example of an artesianaquiferwith water being recharged

from topographicallyhigher outcropson both the Zuni and Defiance

uplifts. Prior2todepressurization,the hydrostaticpressurewas

120.2 kg per cm (1,710psi). Grain sizes range from mediu~ to

coarse,and compressivestreng~hsrange from 94.9 kg Per cm

(1,350psi) to 348.7 kg per cm (4,96opsi). Note that the lower

range for compressivestrength is lower than the originalhydro-

static pressure,indicatinga possiblerunning sand conditionif

sinkingshould be attemptedin the absence of de ressurizationor

8

grouting. Water temperatureis approximately48 C (118F).

959

Depressurization Wells The Phillips Uranium Corporation has put

into operationand maintaineda series of depressurizationwells

in the area of the shafts to reduce the hydrostaticpressure in

the major aquifersin order to facilitateshaft sinking.

Six

wells were drilled through the Gallup Sandstone,four wells in the


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980 1981 RETC PROCEEDINGSVOLUME 2

Dakota Sandstone and six wells in the Westwater Canyon Member.

The casing was slotted throughout the total length of each aquifer

and the pump settings were generally just above each aquifer.

Number Months

lni.tial Residual

Formation

Wells Pumped Yield

Pressure Pressure Effect

Gallup

6 17

1080 gpm

1038

psi

135 pai 82

Dakota

4 14

1120 gpm 1537 psi

350 psi

77

Westwater

4- 6

6 1760 gpm 1711 psi 238

pSi

86

Table 1. Summary of Results of DepressurizationWells

As can be seen from the results summarizedin Table 1, the program

has been highly effective. More perspectiveconcerningresidual

formationpressurescan be gained by the followingestimates,

preparedby PhillipsUranium Corporationgeologists,of potential

inflows to both shaftswith and without the repressurization

wells.

With Without

Formation Wells Wells

Gallup 1,080 gpm

2, 307 gpm

Dakota

1, 120 gpm 2,562 gpm

Westwater 2,212 gpm

5,020 gpm

Table 2. PotentialInflowEstimates

Althoughthese potentialyields with the benefitof the wells

would by no means prohibitshaft sinking,the water inflow from

the upper

aquifers was further reduced by chemical grouting of the

formations prior to sinking.

Grouting

Carrying large volumes of water on the shaft bottom during

sinking probablypossessesthe greatestsingle detrimentto high

shaft sinking productivity.

For the most part, the system of

depressurizationwells had the effect of reducingpotentialin-

flows from the upper aquifersduring sinking to around 4,I6o

liters per minute (1,100gpm). As mentionedabove, these inflows

would not necessarilyprohibitsinking,although carryingthese

volumes of water would have the dual effect of increasingcapital

expenditurescaused by slower shaft sinking rates and increasing

future operatingexpensescaused by pumping larger quantitiesof

water over a significantportion of the mine life.


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961

From the above, it was apparent that further reduction of

potential inflows from the major aquifers would be beneficial if

the reductions could be obtained at a reasonable cost.

Owing

largely to the success of Harrison Westernts chemical grouting

program at the Gulf Mineral Resources Companys M.. Taylor Pro-

ject, it was decided to instigate a similar program at the Nose

Rock Project for the upper aquifers.

No grouting is planned for

the mineralized Westwater Canyon Member since any potential in-

flows will be fully realized during mine development.

I t should be recognizedthat the groutingprocess itself is

expensiveas it is not uncommon to spend one to two months treat-

ing 30 m (100 ft) of shaft.

In addition,initialapplicationsare

highly beneficialbut time spent attemptingto obtain a Iperfect

curtainis subjectto the law of diminishingreturns.

Theoret-

ically, the right amount could be determinedby adding the cost of

groutingto the incrementalsavingsof shaft sinkingcosts due to

grouting,and comparingthe totals to the after tax discounted

cash flow savings of incrementalmine life pumping expense.

Supposedly,if this comparisonyielded a positivenet present

value, further groutingwould be warranted.

The extreme diffi-

culty of estimatingaccuratevalues for the above parametersis

obvious and therefore,the outcome of any attempt must be viewed

with suspicion.

Grout Materials The grouting agents used at Nose Rock were

selectedprimarilyon the basis of successfuluse on other similar

projectsin the Grants Mineral Belt.

CEMENT: All of the sandstoneaquifersrequiringgrout treat-

ment were of fine enough porosityto preclude the use of suspen-

sion type groutingagents.

Cement grout was used primarilyto

stabilizethe rock mass around the concretegroutingpad and to

seal leaks where the pad joined the shaft lining.

Pumped cement grout was mixed with water in water to cement

ratios that varied from 12:1 to 1:1 by weight.

CHEMICALRESIN GROUT: A water soluble resin prepolymerwas the

primarygrouting agent used at Nose Rock. The resin is supplied

as a fine powder which readily dissolvesin water, and in the

presenceof catalystsand accelerators,forms an irreversible,

impermeablegel.

The mixture normallyhas a viscosityclose to

that of water and can thereforebe injectedinto formationsof low

porosity.

The set time or gel time is the time elapsed to form a stiff

gel after the chemicalsare mixed.

For the most part, gel times

can be predictedand controlledby varying the concentrationof

the solutionandlor the addition of a sodium silicate


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962

1981 RETCPROCEEDINGS VOLUME 2

accelerator.

Gel times are also a functionof temperaturewith

the relationshipbeing inverse.

Two

variations of chemical grouting agents were

used at the

Nose Rock Project.

The first type was characterizedby the resin

and caustic soda catalystbeing packagedseparately.

The second

type is packagedtogetherwith other modifications. Care in

transportationand storageof the second type must be exercisedto

preventthe reactionfrom taking place in the bags prematurely.

GroutingEquipment The equipmentselectedwas based on successful

experienceon similar projectselsewhere.

PUMPS AND MIXING TANKS: A double-actng recirculationtype

pu~p capable

3

of pumping at

345

kg per cm (4,900psi) at 8 kg per

cm (100 psi) air pressurewas used.

The pump is modeled after

the South African type grout pump.

Two mixing tanks were equipped

with air poweredmixing and agitationpaddles with one tank

elevatedabove the other.

The tanks were sized to mix the con-

tents of one 23 kg (50 lb) bag in the most dilutedmix of 129 1

(34

gal). One bag was mixed in the upper tank while a solution

was being pumped from the lower tank.

JUMBO AND DRILLS: The grout jumbos consistedof two drill

buggies which circled the shaft on a single track from a pivot in

the center of the shaft.

High speed,air powered, chain fed

rotary drills with 1.5 m (5 ft) feed were used with EX diameter

drill rod.

MISCELLANEOUSEQUIPMENT: Schedule 80 pipe of 5 cm (2 in)

diameterwas used for stand pipes.

These were coupledwith drill

through ball valves of similar diameter. Blow-outpreventers

capable of closing an EX drill rod were also used for added

safety.

GroutingProcedure Normally,one or more probe holes were drilled

into each aquifer from a safe distanceabove. The probe hole

served the dual purpose of determiningthe exact locationof the

aquiferand finding suitablestrata to pour the groutingpad.

Normally the pad was located from 6 m (20 ft) to 9 m (30 ft) above

the aquifer.

GROUT PAD: When the predetermineddepth was reached, the

excavationwas done for the grout pad. The curb or lower ring

of the shaft form was removedand the pad poured, forminga solid

concreteplug poured tight againstand keyed under the shaft

lining. The plug was designedto withstand the anticipated

grouting pressure. While the pad was curing, the jumbo was set up

and the standpipesinstalled.

Before grouting commenced,every

standpipewas tested to full groutingpressure.


10/22


Upon completionof the above, the holes were drilled 3 m

ft) to 6 m (20 ft) and the rock mass between the pad and the

aquifer was injectedwith cement to consolidatethe mass and

leaks between the pad and the shaft lining.

963

10

seal

GROUTING:

Due to widely varying porositiesand local fractur-

ing conditions,experiencehas shown that precalculatedgrout

quantitiesfor a given aquifer are unreliable. As a result, holes

were pumped to refusal at a predeterminedpressureinstead of a

predeterminedquantity.

The groutingpressurewas determinedby

the amount of residual formationpressureto be overcomeand the

acceptabilityof the formationdue to grain size, porosity,

fracturesand other characteristics. Normally, this pressurewas

approximatelytwice the hydrostaticpressurecalculatedfrom the

surface,and many times the residualhydrostaticpressure due to

the effect of the depressurizationwells. A curtain length of

30

m (100 ft) was

the

approxi mate

maximum depth that could be grouted

from one pad.

The hole pattern was designedto interceptas many fracturesas

possiblewith the distancebetween holes at the base of the cur-

tain not exceeding 1.4 m (4.5 ft). The aquiferwas grouted from

the top down in stages of 3 m (10 ft) and all holes in the pattern

were grouted to refusalbefore deepeningthe holes to advance the

cover.

(SeeFigure 3)

Generally,75 -

90% of the potentialinflowswere sealed off

by the grout curtains.

SHAFT SINKING

For the most part, the shaft sinkingmethods used at the Nose

Rock Project can be classifiedas conventional. Methods and

techniquesemployedon any project depend, to a large extent, on

safetyand health regulationspromulgatedby appropriateregula-

tory agencies at both state and federal levels. At the federal

level, the project falls under the Federal Mine Safety and Health

Act of 1977 (PublicLaw 95-164) and is administeredby the newly

createdMine Safety and Health Administration of the Department of

Labor.

subsequent to enactment of the ~977 Act, the New Mexico

Mine Safety Code has adopted the federal standardsas their own.

In addition,the state of New Mexico periodicallydevelops

stricterstandards,mostly as a result of previousserious acci-

dents. The most importantof these to the shaft sinker is a

requirementlimitingunsupportedground in verticalshafts to 3 m

lo f ).

The two shafts are generallyscheduledto be sunk together.

The resultingplan representsthe earliestpossiblecompletion


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964


VERTICMSCME

FMMATION

mri

LUG

WTER BEMINC

SANDS

I

1

I

\__ ..51,00

VERTICALCROSS SECTION

OFDRILLOLE

PLAN TYPICALDAKOTA GROUT COVER

FIGURE 3. PLAN-TYPICALDAKOTA GROUT COVER


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965

date and allows the fresh air base to be lowered when connecting

stations are reached in order to counteract the high temperatures

caused by hot water emanating from various aqui-fers.

Sinking Equipment

The permanentproductionhoist and headframeare used for

sinking the 5.5 m (I8 ft) diameterproductionshaft. The hoist is

a 1,119kw (1,500hp) double drum, double clutch unit, capable of

610 meters per minute (2,000 fpm) line speed. A temporaryhoist

and headframeare used for sinking the 4.9 m 16 ft) ventilation

shaft. The hoist is a 1,007kw (1,350hp) double drum, single

clutch unit capable of 579 meters per minute (1,900 fpm) line

speed. Hoist ropes are 38.1 mm (1.5 in) diameterand are of 18 x

7 non-rotating right lang lay construction.

Compressed alr is supplied to both shafts by seven electrically

powered rotary compressors located on the surface. A portable

concrete batching plant is used to supply concrete into transit

trucks that mix and deliver it to t e respe tive shafts. Concrete

9?

is transported underground in 2.7 m 95 ft ) buckets.

Galloway stages are suspended by four 25.4 mm 1 in) locked

coil ropes and are

used in each shaft as work platforms.

Each

Galloway consistsof four decks and weighs approximately31,070kg

(65,000lb).

The locked coil ropes serve as crossheadguides for

the counterbalancedbuckets.

The Galloway stagesare raised and

loweredby four winches that are electricallywired to operate

together,although any winch can be clutchedout by hand in order

to periodicallybalance tensionbetween the ropes. The rope speed

of the Gallowaywinches is about 2.4 meters per minute (8 fpm).

The Crydermanshaft mucker anchoredto the liningwith brackets

is used for mucking (excavationof blastedmaterial). Invented

and developedin Canada, the mucker is essentiallyan air powered

clamshellmounted on a telescopingboom.

Positioningcylinders

and the telescopingfeaturesof the boom itself allow positive

crowd at any locationon the muck pile.

The machine is controlled

by levers actuatingtwo four-wayvalves, with the left hand con-

trollingboom positionand the right hand controllingthe

clamshelland the telescopingfeatureof the boom.

Two units are

used in the larger productionshaft and a single unit in the

ventilationshaft.

In all cases, the units are suspendedon cable

winches located on the surfacewith the rail and bracketanchoring

39

ystemsal owing v rtical movement only. Muck bucket izes ran e

Y l

from 2.7 m

95 ft ) in the ventilation shaft to 3.5 m 123 ft )

in the production shaft.

Drilling is done with 28 kg 62 lb) hand-held. sinkers with a

piston diameter of 67 mm 2-5/8 in). Drills are lowered in a


13/22

966

1981 RETCPROCEEDINGSVOLUME 2

speciallydesignedbasket containingall materialsrequired for

the operation.

The concreteforms are of all steel construction of the appro-

priate diameter with a length of 3 m 10 ft). The forms are

constructed of four vertical sections of .75 m 2.5 ft) length to

enable any multiple of .75 m 2.5 ft) pour to be made if ground

conditions are poor.

The curb ring is of blast proof construction

and contains the ring blockoutnecessaryto enable pouring the

subsequentpour below.

The top Pmatcherting laps the previous

pour and containsthe guillotinedoors that are closed after the

form is filled with concrete. The form itself is suspendedfrom

the previouspour by six hanging rods.

TypicalSinking Cycle

Due in most part to the wet conditions,the benchingmethod of

excavationis used. This techniqueprovidesa lower area for an

electricsubmersiblepump to be placed after each blast.

More-

over, the blowovernprocess of cleaningthe bench in preparation

for drillingallows a thoroughexaminationfor misfires and the

rock mass thrown by the blast is directed at the shaft walls

instead of the Galloway, thus minimizing damage.

The cycle describedbelow may vary in duration from as little

as 14 hours to as much as 34 hours, dependingon conditions.

Sinking rates for both shafts are comparable. The larger produc-

tion shaft has an advantagewith the additionalCrydermanmucker,

but this seems to be offset by the lesser volume of muck and a

somewhatfaster concretecycle in the ventilationshaft.

Drill and Blast This segment of the cycle begins with a thorough

blow over of loose muck into the sump created by the preceding

bench. Forty to fifty 2.4 m (8 ft) holes are drilled and charged

with a semigelatindynamite.

The dynamiteselected is a reason-

able compromisebetween the desired characteristicsof adequate

strength,low fumes, good water resistanceand cost. A non-

electricdelay blastingcap systemhas been used for detonating

explosiveswith reasonablesuccess. The crews remain on the

surface for a few minutes while the smoke clears.

(SeeFigure 4)

Mucking,

The Cryderman mucker s) are lowered and mucking begins.

Normally, the bucket chains remain attached to the hoist hook and

swivel during loading.

Since the boom llft (not in or out) opera-

tion is the most time consuming,Crydermanoperatorssoon learn to

excavatea hole for the next bucket which tends to save time.

While the loaded bucket is hoisted and dumped, the Cryderman

operator(s)can move muck from hard to reach to convenientplaces

which also conservestime. Buckets are dumped with a lazy chain

controlledby a toplanderfrom the crowqsnestn in the

headframe.

(See Figure 5)


14/22


967

FIGURE 4. DRILLINGTHE BENCH


15/22

9 8

98 RET PRO EEDINGS VOLUME 2

FIGURE 5 MUCKING


16/22


17/22

970

1981

RETC PROCEEDINGSVOLUME 2

FIGURE 6. SETTING CONCRETEFORMS


18/22


971

that attaches the weep pipe to the form. After the curb ring is

lowered, the pipes are attached to the form with a fastening

device that threads into the couplingand allows the water to come

throughthe form.

The curb ring is then filled with concrete

forming a tight seal for the bottom of the pour. After the

remainingform is loweredand poured, the water flows freely

through the weep pipes.

These are later connectedto a 10.2 mm

(4) drain line which carries the water into a pump station or a

super water ring discussedfurtherbelow.

Super Water Rings The in-shaft pumping system consisted of 43 kw

58 hp) submersible pumps on the bottom and staged up the shaft

wall in distancesnot exceeding

61 m (200

ft). The electric

submersiblepumps of this type require frequentmaintenanceand

normally this must be done on the surface.

To facilitatepump

changeoutand providea sump for staged pumps, HarrisonWestern

engineersdevelopedthe fsuperwater ring.

Essentially,the

super water ring is the enlargementof a 3 m (10 ft) vertical

section of the shaft by .6 m (2 ft) in radiuswith a .6 m (2 ft)

steel dam installedflush with the shaft lining.

Submersible

pumps in these rings eventuallytransferwater to temporaryor

permanentpumping stations.

FiberglassWater Rings The purpose of the fiberglasswater ring

is to collect water running on the inside of the shaft lining.

The rings are installedabove pump stations,super water rings or

periodicallywhen needed,and are connectedwith hose or piping to

the drain line, super water ring or station. They are fabricated

to attach to the concreteform and are easily installed.

Bonus and Incentives

In

recent years, industrial managers have gravitated towards

the theories of motivation espoused by such management theorists

as Fredrick Herzburg et al.

These theories stress job

enrichment or other such enlargementof an individualstask or

area of responsibilityas a motivatingforce in order to otherwise

offset the boredom and dissatisfactionthat often accompaniesthe

modern industrialwork setting.

For the most part, these theorists would deny that additional

remuneration is a motivating factor per se, although admitting

that substandard pay scales can be a source of considerabledis-

satisfactionamoung a work force.

Undergroundconstructionand

mining in the Rocky Mountainsand in a large portion of Canada are

some of the last bastionsof the piece work system still existing

in North America, albeit in modified form.

Seeminglyin defianceof modern managementtheory, the Nose

Rock Projecthas successfullyapplied two forms of bonus


19/22

972


incentivesaffectingall contractorpersonnelon the project. The

first is a direct bonus which is paid only to those working below

the shaft collar.

This bonus is basicallya piece rate system

applied to the crew as a whole with a guaranteedminimum base rate

for each man.

The second form of bonus is paid to all others not

receivingthe first and is based on a review of the overall pro-

ject status comparedwith the originalproject schedule. This

bonus is paid (if earned) every calendarquarter as a percentage

of the base wage rate.

Sinking Rates Attained

Shaft sinking rates of 3 meters per day (10 ft per day) were

regularlyattained,even throughmost major aquifers,and rates of

30 meters per week (100 ft per week) were regularlyattained

throughmuch of the Mancos shale.

The productionshaft crew

achievedan area record of 36.3 meters (119 ft) of completedshaft

in one week of seven days.

The ventilationshaft crew achieveda

one month productionof 132.6meters (435 ft) of completedshaft,

also believed to be an area record.

PUMPING SYSTEM - TEMPORARYAND PERMANENT

Dependablepumping systemsare an absolutenecessityto the

constructionand operationof a mine such as this one with the

shafts penetratingfive major aquifersand the ore itselfhaving

been depositedin the matrix of the fifth, the Westwater Canyon

Member.

Extensiveplanningwas requiredby both the Phillips

Uranium Corporationand HarrisonWestern Corporationto insure

that the systemwas reliable for sinking,mine developmentand

later for ore extraction.

The two permanentpump stationsrepre-

sent the system requirementfor mine developmentand ore extrac-

tion. Unfortunately,this system is not entirelyadequate for

sinking the shafts and as a result, the permanentsystem was

augmentedby a series of temporarypumping stationsfor sinking.

Of prime considerationwhen locatingpumping stationsis the

capabilityof the equipmentitself and the selectionof suitable

strata in which to locate the station.

The sandstonesto be mined

can be expectedto yield a certain amount of sand particulateto

the dischargewater and even with the benefit of a desanding

facility,the pumps must be able to pump water containingsand

particulate.

For this reason and the fact that desandingequip-

ment is not availablefor sinking,less efficientslurry type

centrifugalpumps were selected.

These pumps enjoy wide popu-

larity at other mines in the Grants Mineral Belt, mainly for their

ability to pump water containingabrasivesolids over long periods

of time with low maintenancecosts.


20/22

Permanent Pump Stations


973

The two permanent pump stations at the Nose Rook Project were

des@ned for a sustained pumping capability of Z2,700 liters per

minute, 6OOO gpm) with an additional11,350liters per minute

(3,000

gpm

backup.

These stationsconsist of three banks of five

pumps per bank with each bank being capable of pumping 11,350

liters per minute (3,000 gpm). Provisionswere made in each

station to install a fourth bank of equal capacitysometime in the

future,should conditionsdictate.

The primary pumps of each bank are 313 kw (500 hp) electrically

powered,direct driven centrifugalslurry pumps, each capable of

11,350

liters per minute (3,000gpm) at a total dischargehead of

137 meters (450 ft]. These pumps are connectedin series to

attain the desired system head and in all cases are force fed with

high volume, low head feed pumps, to minimize the effects of

cavitation. The last pump of each bank is equippedwith a fluid

couplingwhich, in conjunctionwith electricmetering and feed

back of sump water levels, can automaticallyregulateoutput to

allow continuousoperationat levelsas low as 6,o5o liters per

minute (1,600gpm).

The upper permanentpump station is located 457 meters (1,500

ft) below the surface.

Each bank of pumps on this station con-

sists of three main pumps connectedin series and force fed by two

feed pumps, also connectedin series. The lower permanentpump

station is located at 957 meters (3,140 ft) below the surface and

when completedwill dischargeinto sumps on the upper station.

The typical bank on the lower station consistsof four main pumps

in series force fed by a verticalcentrifugalpump which will be

located in a sump on the haulage level 23 meters (75 ft) below.

TemporaryPump Stations

Temporarypump stationsare normallylocated above major

aquifersin order to minimize the less reliablein-shaftsuper

water ring system describedearlier.

These stationsare equipped

with either the primarypumps describedearlier or a smaller

version capable of 7,570 liters per minute (2,000 gpm) at a total

dischargehead of 98 meters (320 ft). The maximum lift for a

temporarystationwas 305 meters (1000 ft).

Five temporarypump stationswere used for shaft sinkingat the

Nose Rock Project. These stationseither dischargedinto higher

temporarystationsor permanentstations. As permanentstations

were completedand became available,they were incorporatedinto

the system.


21/22

974

1981 RETCPROCEEDINGSVOLUME 2

CONCLUSION

The Nose Rock Project is currentlyrunning approximatelythree

months ahead of schedule. Althoughno methods or techniqueshave

been used that could be classifiedas unconventional,through a

combinationof experiencedmanagement,proven water control

techniques,well structuredbonus incentiveplans, and a positive

overall relationshipbetween owner and contractor,record sinking

rates have been attained.

When completed,the Nose Rock Project will unlock for public

use a considerableamount of uraniumore from deep underground.

Combinedmanagmentand technicalachievementsof both Phillips

Uranium Corporationand HarrisonWestern Corporationare

responsiblefor this success.


22/22


975

REFERENCES

chenowith, W.L. , 1977,

tUraniumin the San Juan Basin - An

Overview,WNew Mexico GeologicalSociety Guidebook,28th Field

Conference,San Juan Basin III, pp. 257-262.

Greenslade, W.M., Sprouls, E.P., 1977, Geotechnical and

Hydrologic Investigation, Production Shaft, Mining Unit 1,

Nose Rock Project, Dames and Moore, Phoenix, Arizona.

Griswold,G.G.,

White, L.G., 1980,tWaterControlDuring Shaft

Sinking UtilizingDepressuringWells and Resin Grouting

Techniques,nHarrisonWestern Corporation,Denver, Colorado.

Kelly, T.E.,

1977,

W3eohydrology of the WeStWaterCanYon Member~

MorrisonFormation,of the SouthernSan Juan Basin, New

Mexico,nNew Mexico GeologicalSociety Guidebook,28th Field

Conference,San Juan Basin III, pp. 285-290.

Molenaar, C.M., Y3tratigraphy and Depositional History of Upper

Cretaceus Rocks of the San Juan Basin Area New Mexico and

Colorado, with a Note on Economic Resources,n New Mexico

Geoloj@cal Society Guidebook, 28th Field Conference, San Juan

Basin IIILPP 159-166.

Vanderwoude, M.D., 1980,

Mine Geologist,PhillipsUranium

Corporation,Private Communication.

Documents

ShaftSinkingPracticesfor Mining