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Geotechnik - Tunnelbau undTunnelmechanik

Tunnelling:

Management by Design

Kolymbas, D.: Geotechnik - Tunnelbau undTunnelmechanik, Springer-Verlag, Berlin, Heidelberg1998, ISBN 3-540-62805-3, Price: DM 128.00Muir Wood, A.: Tunnelling: Management by design,E&FN SPON London and New York 2000,ISBN 0-419-23200- 1. Price: 40.00

Reviewing together two recently published engineeringbooks on the same topic offers a welcome opportunityfor comparisons. If such books are representative of themain currents of thought in their field, such a doublereview is especially appealing.For decades there has been growing competition toconventional tunnelling from the so-called New AustrianTunnelling Method (NATM). The resulting split in thetunnelling community was recently aptly characterisedby A. Haack, President of ITA: Some regard NATM as acure-all drug and a philosophy, others regard it as apseudo-scientific way of thinking (Tunnel 7/97).Muir Wood's book stands in the tradition of sound

scientific methodology; that of Kolymbas is a fruit of theNATM ideology. The only thing the two works have incommon is a length of around 300 pages. Muir Woodendeavours to communicate his rich experience, gainedover a period of more than 40 years, to the profession,bringing in scientific aspects (among other things in theplanning and execution of the Eurotunnel) wherenecessary. In doing this he can draw examples fromnumerous valuable publications. Kolymbas main aim onthe other hand is, in his own words, to provide themissing theoretical foundation of NATM'. To fulfil thistask - due to the pseudo-scientific nature of NATM -neither practical experience in tunnelling nor recourse to

one's own research work is necessary. In fact, in hiswork Kolymbas does not refer to a single scientificcontribution of his own or to any construction project inwhich he was personally involved. What this leads to willbe illustrated by some examples. First, his approximateformulas, which are intended to explain the principles ofNATM, are based on unrealistic assumptions onlyresulting in an inappropriate and unacceptablemathematical formalisation of tunnelling. It suffices hereto mention his formula for determining the required liningresistance when using a system of grid anchors, inwhich he does not consider the influence of rockdeformation. In this way he not only causes

embarrassment to the proponents of NATM, but alsocontradicts himself, since in a previous chapter herecommends the method of the characteristic line, whichtakes into account the deformation of the rock todetermine the lining resistance. The trough-shapedcharacteristic line proposed by Pacher represents

according to Mller the fundamental concept of NATM'.Kolymbas deals with it in great detail. This in a way isunderstandable, because the NATM literature listsnumerous practical examples for the alleged use of thePacher curve to optimise the rock pressure (TauernTunnel, Arlberg Tunnel, Tarbela Project, UndergroundPower House Waldeck, etc.). In Kolymbas's opinion:in order to get by with as low a lining resistance aspossible, the characteristic line of the lining shouldintersect at point B (minimum of the ground responsecurve) with the ground response curve. This NATMrequirement is directed more to the intuition of thetunnelling engineer, from which - strictly speaking - the

idea of the rising branch of the ground response curvecomes, since the position of this minimum cannot bedetermined. The rising branch appears to be veryplausible, but could not be verified up to now either bymeasurements or by numerical simulation.Kolymbas is perhaps unaware that with this statementhe has made the protagonists of NATM (includingRabcewicz and Mller, who over a period of decadesreported on concrete applications of the Pacher curve)guilty of scientific fraud. Since he cannot produce eitheran empirical or theoretical explanation for the basicconcept and nevertheless claims it is reasonable, herelegates NATM to the realms of fantasy.

How far the author is removed from the realities ofunderground construction is shown in the followingexamples: Short anchors are relatively expensive, sincethe most expensive part is the anchor head. Thus a 24m anchor only costs about twice that of a 3 m anchor.He forgets the costs for drilling the borehole andinserting the anchor. The schematic representation ofthe method of action of slit-rod-and-wedge type of bolts(Fig. 10.3) or the explanation of the kerf cutting in therock by the disc cutter (Fig. 11.1) is basically incorrect.

Also we consider his newly created term tunnelmechanics to be superfluous, for after all, appliedmechanics has been associated with tunnelling for all of

200 years. We now turn to Muir Wood's book. Theauthor's goal is to present tunnelling in a systematic wayand he places his emphasis on the explanation of theprocesses, which during planning, design and executionalways occur in a variety of ways, changing from projectto project. Accordingly, he begins his work with an

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explanation of the term 'system engineering and pointsout the frequent differentiation in industry betweenproduct design and process design (i.e. providing themeans of manufacturing the desired product). As aresult he does not get bogged down in abstractmanagement theory, but fills in the theoretical frameworkwith expert knowledge, which is ordered and weightedaccording to practical criteria. Numerous examples ofsuccessful and less successful projects in manycountries clarify the main points of his discussion. We

know of no other textbook on tunnelling with acomparably large breadth of treatment, beginning with abrief historical introduction, among other topics he dealswith the questions of preliminary planning, financing,contract procedures, site investigations, risks includingtheir distribution, design, execution, geotechnical controlmeasurements as well as project management. Whatimpresses the reader most of all is the rich interplaybetween all these problem areas; in particular thematicinteraction in the different phases of the realisation ofprojects involving underground construction is difficult topresent in a generally valid way. Muir Wood hasachieved this in an excellent manner, because he has

not only directed many projects, but can also look backon an extremely active International professional life: Sir

Alan Muir Wood, as is well known, was the firstpresident of the international Tunnelling Association(ITA). A further special condition which has favourablyinfluenced the coming into being of his work, hesummarises as follows: The immediate spur to writingthis book is that the author has lived and worked througha period of revolutionary change in tunnelling withseveral components.The concise presentation of the demanding topicspresupposes that the reader possesses considerablebasic knowledge and experience in tunnelling. The

formulations are very pregnant, so that perhaps thereader - like the reviewer - has continually to write downsentences, which he does want to forget. Forprofessional colleagues on the Continent the soberBritish pragmatism, for which Muir Wood is anoutstanding example, will definitely stand out positively.Thus he does not leave the reader with the falseimpression of a perfect world of tunnelling - on thecontrary, e.g. when reappraising the events andanalysing the damage following the collapse of theHeathrow Airport Tunnel in London. This chapter of hisbook, as every other, is prefaced by a quotation, whichthose who know the background details will find veryapposite: The curious incident of the dog in thenighttime. The dog did nothing in the nighttime. That wasthe curious incident (A. Conan Doyle).Hardly any reviewed work is not thought to be in need ofsuggestions for improvement. Thus we think that theshort section on analytical computational solutions as anaid to design and construction seems to be alien to therest of the text in which the author helpfully describesthe overall behaviour of the ground; this is particularlytrue for the stress state in the vicinity of a sphericalopening. Thus in the next edition, chapter 8, devoted tothe topic of Hazards, Disputes and Resolution, could bedealt with more explicitly. K. Kovri, Zurich/CH