Why_go_Underground.pdf

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Found ed in 1974, ITA ha s 50 Member Nations a nd 290 Affilia te Memb ers.

The a ims o f ITA are to enc ourage planning of the s ubsurfac e a nd to promote ad vanc es in the prepara tory investigations for tunnels a nd inthe design, construction and maintenance of tunnels by bringing together information thereon and by studying questions related there to.

The Ass oc iation fulfils its miss ion:

by fac ilitating the excha ng e of information among its memb ers by holding public or other meetings by organising a nd co ordinating studies a nd experiments by publishing proce edings, reports and documents.

ITA MEMBER NATIONS ITA MEMBER NATIONS ITA MEMBER NATIONS ITA MEMBER NATIONS

TH I S I S S U E H A S B E E N P R E PA R E D B YJ E A N- PA U L GO D A R D, PA S T VI C E- PR E S I D E N T O F I TA W I T H T H E C O N T R I B U T I O N O F I TA ME M B E R NAT I O N S

Directeur de la publication : Claude Berenguier, AITES - 25 av F. Mitterrand, F-69674 BRON Cedex,+33-478260455, +33-472372406dit par ACROTRE : BP1275 - F-31047 TOULOUSE Cedex 1,+33-561310385, +33-561490522, [email protected]

Imprim par Imprimerie LECHA, 51 rue du Pech - F-31100 TOULOUSE Dpt lgal : Mars 2002

AFRIQUE DU SUD SOUTH AFRICA South African National Council on Tunnelling+ 27-116481876ALGRIE ALGERIA Ministre des Travaux Publics+ 213-2851837ALLEMAGNE GERMANY Deutscher Ausschuss fr Unterirdisches Bauen, + 49-2215979550,A.Haack@ stuva.de

ARABIE SAOUDITE SAUDI ARABIA Ministry of Communications, + 966-14029436ARGENTINE ARGENTINA Association Argentina de Ingeneria de Tuneles, + 54-1149512293,issanoner@ arnet.com.ar

AUSTRALIE AUSTRALIA Australian Underground Construction & Tunnelling Association, + 61-26273 2358,valerie_lee@ ieaust.org.au

AUTRICHE AUSTRIA Austrian National Committee of ITA, + 43-15041596, beton@ netway.atBELGIQUE BELGIUM Association Belge des Techniques et de l'Urbanisme Souterrain, + 32-22873144,willy.delathauwer@ vici.fgov.be

BRSIL BRAZIL Brazilian Tunnelling Committee, + 55-112687325, cbtabms@ metrosp.com.brBULGARIE BULGARIA Geotechnim-SVS , + 359-29650222CANADA Tunnelling Association of Canada, + 1-4164457107, bruce.ripley@ bchydro.bc.caCHINE CHINA China Civil Engineering Society, + 86-18393953COLOMBIE COLOMBIA Comit Colombiano de Tneles, + 57-12856715, cospina@ ingetec.com.coCORE KOREA Korean Tunnelling Association, + 82-25467141DANEMARK DENMARK Danish Society for Tunnels & Underground Works, + 45-43960055, jlo@ carlbro.dkEGYPTE EGYPT Egyptian Tunnelling Society, + 20-25787662,ets@ thewayout.net

ESPAGNE SPAIN Asociacin Espaola de Tneles y Obras Subterrneas, + 34-915233683,aetos@ caminos.recol.es

TATS-UNIS D'AMRIQUE USA American Underground Construction Association , + 1-6128258944,underground@ auaonline.org

FINLANDE FINLAND Finnish Tunnelling Association, + 358-9467927, J [email protected]

FRANCE Association Franaise des Travaux en Souterrain, + 33-147647588, [email protected]. frGRCE GREECE Greek Tunnelling Society,+ 30-15239647, M .Stavropoulou@ mechan.ntua.grHONGRIE HUNGARY Association for Utilization of t he Subsurface Space, + 36-13556182,h13250gre@ helka.iif.hu

INDE INDIA Central Board of Irrigation and Power, + 91-1161116567, cbip@ nda.vsnl.net.in

ISLANDE ICELAND Icelandic Tunnelling Society, + 354-5622332, hrh@ vegag.isIRAN Iran Tunnelling Association,+ 98-216014828ISRAEL Inter Ministerial Committee+ 972-26223058ITALIE ITALY Societ Italiana Gallerie+ 39-026599758, segreteria@ societaitalianagallerie.itJAPON JAPAN Japan Tunnelling Society, + 81-335536145, jta@ sepia.ocn.ne.jpLESOTHO Lesotho Tunnelling Society, + 266-310005MALAISIE MALAYSIA The Institution of Engineers, Malaysia+ 603-7577678, keith@ mtdcap.comMAROC MOROCCO Association Marocaine des Travaux en Souterrain, + 212-22488700MEXIQUE MEXICO Asociacin Mexicana de Ingeniera de Tneles y Obras Subterrneas,+ 52-56062323

NORVGE NORWAY Norsk Forening for Fjellsprengningsteknikk (NFF), + 47-67565533 , postmaster@ nff.noNOUVELLE-ZLANDE NEW ZEALAND Works Consultancy Services Ltd , + 64-44733017PAYS-BAS NETHERLANDS Tunnelling and Underground Works Division of Kivi, + 31-30899608, info@ v-o-r.nlPOLOGNE POLAND Podkomitet Budownictwa Podziemnego, + 48-22264291PORTUGAL Sociedade Portuguesa de Geotecnia, + 351-18478187, jas@ dec.uc.ptRPUBLIQUE TCHQUE CZECH REPUBLIC Czech Tunnelling Committee,+ 420-266793479, matzner@ metrostav.cz

ROUMANIE ROMANIA Association Roumaine des Tunnels, + 40-12420781, stematiu@ hidro.utcb.roROYAUME-UNI UNITED KINGDOM British Tunnelling Society, + 44-2077991325, bts@ ice.org.ukRUSSIE RUSSIA Russian Tunnelling Association, + 7-0952073276, rus_tunnel@ m tu-net.ruSINGAPOUR SINGAPORE Tunnelling and Underground Construction Society, + 65-7921650,tucss@ tucss.com

SLOVAQUIE SLOVAKIA Slovak Tunnelling Association, + 421-745523103, terraprojekt@ gtinet.skSLOVNIE SLOVENIA Slovenian National Committee on Tunnel Construction and Underground Structures,+ 386-15341680, vojkan.jovicic@ i-rgo.si

SUDE SWEDEN BK Swedish Rock Construction Committee, + 46-86111091,nordmark@ bergsprangningskommitten.a.se

SUISSE SWITZERLAND Groupe Spcialis pour les Travaux Souterrains, + 41-332257968,

sia-fgu@ swisstunnel.ch

THAILANDE THAILAND ITAThai Nation Member, + 66-25245509TURQUIE TURKEY Turkish Road Association Erer SA, + 90-3124258210, komite@ ytmk.org.trUKRAINE Ukrmetrotunelbud Corporations,+ 38-0442284997VENEZUELA Socvenos,+ 58-12082620


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O n behalf of the ITA Executive C ouncil (EC ) I have the

p l e a s u re of introducing you this special issue of Tr i b u n e

why go underground ?. I do not need to mentionhow important this topic is to our association and to the enti-

re tunnelling community. In fact, this special issue of Tribune

is an idea dreamt up a few years ago become reality. O n the

occasion of the ITA 25th Anniversary (1999), the ITA EC

decided to publish a position paper on this topic, which

appeared in the book Tunnelling Tec hno logies for th e 3rd

Millennium , distributed in Durban (2000). Then, it was deci-

ded that the impact of the text could be boosted by illustra-

tions with the results published in a special issue of Tribune.

This task turned out to be more complex than initially antici-pated, but under the leadership of Jean Paul Godard and a

great effort of the Team ITA, i t has now been achieved and

is available for the benefits of the entire tunnelling family.

why go underground ? is an answer following up anenormous demand for underground structures due to the

Environmental Era. Nowadays, underground structures are

one of the best solutions for urban problems and for inter-

urban links in mountainous landscape. As regards cities, a

wide range of underground structures have been used to

improve living conditions. T unnels for transportation (motor-

ways, metros) and for public utilities (water supply, sewera-

ge, electrical and telephone cables) are a priority in develo-

ping countries, and underground structures for city centre

revitalisation and for public use (libraries, museums, car par-

king, entertainment and leisure facilities) are of great interest

in developed countries. However, whatever the type of

underground structures in an urban environment, they all

aim to free surface space for more noble human needs,

improving the living conditions of our cities. In the case of

interurban links, long-length tunnels are justified by saving

time and reducing costs (shorter journeys and less energy

consumption), maximizing safety and minimizing environ-

mental impacts.

However, one of the most difficult aspects of implementing

underground structures is to convince urban designers,

politicians, decision makers about their needs and benefits.

why go underground ? is one of the ITAs responsesto meet this challenge. The ITA has acquired knowledge on

this issue and is now releasing the information it has gathe-

red. It is our goal that why go underground ? helpsclose the gaps between our tunnelling community and

those who decide the priorities of our societies. We are

hopeful that why go underground? will be an impor-tant IT A contribution towards a better use of underground

space and sustainable development of our world.


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For hundreds of thousands of years, our natural domainhas been a principally two-dimensional space : the surfa-ce of the ground.

Urged by necessity, curiosity, and even by temerity, wehave always tried to escape from this space, either bywidening it, which is only possible in a very restrictive

sense, or by searching to utilize the third dimension,upwards or downwards. In these efforts, we have alwaysencountered great difficulties that have been overcomethanks only to an astonishing tenacity.

So it has been and so it still is in the conquest of the conti-nents, the oceans, or outerspace. So it is for the use ofunderground space.

In this field, as in the others, nature provides many chal-lenges and we must doggedly gather our experiences,draw lessons from failures, improve techniques and useall our resources of inventiveness before succeeding.

Underground works have always been difficult but this didnot prevent their use at a very early stage of human deve-

lopment, as proved by the discovery of undergroundexcavations that are among the first records of humanactivity.

Of course, nature,and not mankind, isat the origin of the

first undergroundworks. Grottos andcaves are the resultof the action of therain, the rivers and

the sea, and vital

necessity droveearly humans to sett-le in these naturalcavities, no doubt to find protection from the weather and

from attacks. On this point, it is tempting to think thathumanity perhaps owes its survival largely to these naturalhabitats.

Cavemens' dwellings were an important landmark inthe use of under-ground space bymankind ; withthem, the use of

the undergroundbecame intentionaland active.

In every age,

considerable use

Fig 3 : Cave dwelling(France)

Fig 2 : A natural cavern

Fig 1 For hundreds of thousands of years, our natural domain has bee n a principally two-dimensional space

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has been made of undergroundstructures for mining and defen-sive purposes.

H o w e v e r, the most rapid increa-se in the use of undergroundworks only appeared in the 19th

and particularly the 20th centu-ries, thanks to the impetus ofeconomic development.

During these periods, there wasa dramatic increase in under-ground space use, in mining, in

the field of transportation withthe development of roads,

waterways, and railways , andin the field of hydroelectric faci-l i t i e s .

So, since the dawn of human endeavor - more intensi-vely during the recent centuries, and above all duringthe last decades - numerous reasons have encoura-

ged mankind to use and develop underground space.

For a good understanding of these reasons, it is

necessary to keep in mind certain fundamental cha-racteristics of underground space.

First, the underground medium is a space that canprovide the setting for activities or infrastructures thatare difficult, impossible, environmentally undesirableor less profitable to install above ground.

Another fundamental characteristic of undergroundspace lies in the natural protection it offers to whate-ver is placed underground. This protection is simulta-neously mechanical, thermal, and acoustic.

On the other hand, the containment created byunderground structures has the advantage of protec-

ting the surface environment from the risks and/or dis-turbances inherent in certain types of activities.

L a s t l y, another important feature of underground

space is its opacity. Thanks to the natural visual

screen created by the geological medium, an under-ground structure is only visible at the point(s) where itconnects to the surface.

But what are the main reasons today which justify amore intensive and a better-planned use of the under-ground space?

Fig 5 : The Sa int Gotthard Tunnel(Switzerland)

Fig 4 : The Malpas Tunnel onthe Canal du M idi (France -late 17th Century)

Fig 6 : Powerhouse o fthe Serra da MesaHydroelectric PowerPlant (Brazil)

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GO UNDERGROUND FOR LAND USE AND LOCATION REASONS

In many cases, underground spaceuse results from a lack of surfacespace.

The use of underground spaceallows a facility to be built in a loca-tion where a surface facility is notpossible either because of lack ofspace or because building a surfa-

ce facility in that location is notacceptable to the community.There are many types of facilities

that are best or necessarily placedunderground because their physi-

cal presence on the surface is unwanted, for example :public utilities, storage of less-desirable materials, and carparks.

Also, there is often the need to separate conflicting trans-

port activities or to provide easy connections among them.

The distribution of pedes-trians around major train

stations and bus/train inter-changes are examples of

this type of need. Gradeseparation of corridors isoften desired and placing

one corridor undergroundgenerally impacts far lesson the existing community.In urban areas, several levels of transport facilities can bebrought together in the important city transport hubs.

The underground solution also allows one to build in closeproximity to existing facilities or on otherwise unbuildablesites, thus offering better services to the users.

Fig 7 : Blaak Station -Rotterdam (The Netherlands)

Fig 10 : Tokyo SubwayIidabashi Station (Japan )

Fig 9 : Le Grand Lo uvre (Paris)

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Fig 8 : Underground Expansion of

Swedens Royal Library Fig 11 : La DfenseUrban Hub (Paris)


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GO UNDERGROUND FOR ISOLATION CONSIDERAT I O N S

The ground is massive and opaque and provides a varie-ty of advantages in terms of isolation. Isolation is an

important reason for placing facilities underground.

CLIMATE

The underground provides isolation from all climates. Thetemperature within the soil or rock offers a moderate anduniform thermal environment compared with the extremes

of surface temperatures. These moderate temperaturesand the slow response of the large thermal mass of theearth provide a wide range of energy conservation and

energy storage advantages. Thus, theunderground provides both protection

from adverse climates and substantialenergy savings.

Fig 14 : Gjovik Olympic Mountain Hall (Norway)

Fig 12 : Underground swimming pool (Finland)

Fig 15 : The San ta Claus Village, unique Christmastheme park on the Arctic Circle in Finnish Lapland

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Fig 13 : Underg round ho spital potash sa lts mining for allergy treatment - Ural (Russia)


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NATURAL DISASTERS AND EARTHQUAKE

Underground structures are naturally protected fromsevere weather (hurricanes, tornadoes, thunderstorms,

and other natural phenomena). Underground structurescan also resist structural damage due to floodwaters,although special isolation provisions are necessary to pre-vent flooding the structure itself.

Moreover, underground structures have several intrinsicadvantages in resisting earthquake motions; they are lessaffected by the surface seismic waves, as it has beennoted notably on the occasion of the Kobe earthquake in

1995, and previously in San Francisco and in Mexico City.

The structural oscillation effects are limited, since they areconstrained to move with the ground motion. Besides, asthey are designed to support important ground loads, theyoften can better resist earthquake loadings.

PROTECTION

Underground structures offer advantages in terms of pre-servation of objects or products stored within the structu-re. For example, food preservation is enhanced by themoderate and constant underground temperature condi-

tions and the ability to maintaina sealed environment.

Small amounts of earth cover arevery effective at protecting fromthe transmission of airborne

Fig 16 : Above-ground structures are moresensible to earthquake than undergroundones - Kobe Earthquake (Japan - 199 5) -Severe damage to the Kob e City Hall - Nodamage to the underground shop ping malllocated below.

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Fig 17 : Underground Storage Facilities inKansas City (USA)

Fig 18 : Underground Crude Oil StorageFacility - Kuji Plant (Japan)


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noise. Similarly, if the vibrationsources are at or near theground surface, levels ofvibration will diminish rapidlywith depth below ground anddistance of the source.

As with noise and vibration,the earth provides protection by absorbing the shock andvibrational energy of an explosion.

In cases of explosion, radioactive fallout, and industrialaccident, underground structures can be valuable emer-gency shelter facilities, if provided with the ability toexclude or filter contaminated outside air.

Fig 19 : Church in the Rock in Helsinki (Finland) Fig 20 : University of Minnesota (USA)

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CONTAINMENT

Containment is the inverse function of protection. This isvery important for protecting the surface from the nui-

sances and dangers generated by some facilities like

hazardous material storage and hazardous processes.Examples include the storage of nuclear waste far from

human activity and possibly even hazardous industrialplants such as nuclear reactors.

SECURITY

The principal security advantage for underground facilities is

that access points are generally limited and easily secured.

GO UNDERGROUND FOR ENVIRONMENTAL PRESERVAT I O N

The ground also provides a variety of advantages in termsof protection of the environment. These are notably impor-

tant aspects in designing facilities with a low environmen-tal impact.

AESTHETICS

A fully or partially underground structure has less visualimpact than an equivalent surface structure.

Fig 21 : Yucca Mou ntain SiteCharacterization Project (Nevada, USA)

Fig 22 : Car park at the squareEstienne d'Orves in Marseilles

(France) - Situation "before" and

"after" the construction of the

underground car park

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This may be important tohide unattractive techni-cal facilities in sensitive

locations or whenindustrial facili-ties must be sitedadjacent to resi-dential areas.

This is alsoimportant for thepreservation ofnatural land-

scapes.The increasingrequirement forall utility servicesto be placedu n d e r g r o u n d

stems essentially

from visual impact considerations and concerns aboutprotection against the elements.

Fig 23 : Thanks tothe use of subsur-face, a car parkcould be located

in the very proximi-ty of the SydneyOpera House(Australia)

Fig 24 : Variety of the underground infrastructure of a city

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ECOLOGY

In some cases, underground structures helppreserve natural vegetation. Less damage is

thus inflicted on the local and global ecologi-cal cycle.Plant life, animal habitat and passages, andplant transpiration and respiration are main-tained to a greater extent than with surface

construction.

Fig 25 : A motorway tunnel forming a green bridge, providing afree range for peop le, animals, and even vegetation. (Finland)

Fig 26 : The Green Heart Tunne l (The Netherlands)

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GO UNDERGROUND FOR TOPOGRAPHIC REASONS

In hilly or mountainous areas, the use of tunnelsimproves or makes feasible various transport optionssuch as roads, railways, canals, etc. Tunnels are alsoan important option in river, straits and harbour cros-s i n g s .

Generally speaking, underground space use off e r smany advantages with regard to the layout of facilitiesand infrastructures. These advantages derive essen-

tially from the freedom (within geological, cost, andland ownership limitations) to plan a facility in threedimensions and from the removal of physical barrierson the land.

Fig 28 : Mont Russelin Tunnel - National Highway A16 (Switzerland)

Fig 27 : The GotthardBase Tunnel (Switzerland)

Fig 29 : High sp eed railway tunnel (Germany)Fig 30 : Trans- Tokyo Bay

Highway (Japan)

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Fig 31 : The Noor d

Tunnel - Amsterdam(The Netherland s)

Fig 32 : ExpandedUse of Underground

Space

Fig 33 : The newAntwerp Central

Station on the ParisAmsterdam HighSpeed Rail Link

(Belgium)

2006

1900

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GO UNDERGROUND FOR SOCIETAL BENEFITS

Cities that are capable of func-tioning both in social and hygie-nic terms form the prerequisitefor a decent life in built-upareas. Underground space has

an important role to play in thisrespect, i.e. in the achievementof environmentally-friendlydevelopment, whether it be inthe reduction of pollution or

noise nuisance, the eff i c i e n t

use of space, economic deve-lopment, the preservation of theliving environment, public healthor safety. In these fields, it off e r s

numerous advantages.

Tunnels play a vital environ-mental role by conveying clean

water to and by conveying was-tewater out from urban areas.

Tunnels provide safe, environmentally sound, fast, andunobtrusive urban mass transit systems.

Fig 35 : Waste watertreatment plant in

Helsinki (Finland)

Fig 34 : The Lesotho Highlands

Water Project

Fig 36 : Paris MetroMeteor Line 14

(France)

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City traffic tunnels clear vehicles from surface streets,

traffic noise is reduced, air becomes less polluted and thesurface street areas may partially be used for other pur-poses.

Fig 38 : Paris RegionThe A86 West UndergroundLink-up (France)

Fig 37 : The Central Artery - Boston (USA)

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Underground car parks and shopping malls in citycentres leave room for recreation areas and playgrounds

above ground.

Multipurpose utility tunnels are less vulnerable to exter-nal conditions than surface installations and will causeonly insignificant disturbance above ground when instal-

led equipments are repaired or maintained.

Fig 40 : The Paris Town Hall underground car park (France)

Fig 41 : U tilidor - ParisFrance

Fig 39 : Und erground car park below a schoolyard - Stockolm (Sweden)

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Economical aspects wrongly remain a major barrier to thedevelopment of the use of the underground space.

Since the initial construction cost of underground struc-tures is generally higher than those of building in the openair, underground structures are in a sense penalized when compared to open air construction on this restricted

basis.

Thus, the economical benefits of an underground facilityshould be calculated by estimating the life-cost impacts of

the benefits provided by such a facility.

Moreover, the assessment of the underground structuresshould take into account the various indirect advantages

they offer, notably with regard to the environment.

TAKING INTO ACCOUNT LIFE-CYCLE COSTS

In a long-term use, underground construction may well proveeconomical. The benefits may concern initial cost or opera-ting cost.

LAND COST SAVINGS

The most obvious initial cost saving related to an under-ground facility is in a reduced cost for the land purchase oreasement necessary to carry out the project. In areas with

extremely high land costs , the cost of land purchase candominate all the initial cost decisions, especially in the heartof major cities.

But one of the main advantages of placing a facility under-ground is that one can significantly increase the useful-ness, and thus the value, of the land. Originally man builtjust on the surface itself. Construction underground

doubles the useable value of the land in the same waythe value of the land is enhanced by construction of

multi-story facilities. In many cases, all three : surface,underground, and air-rights are used to maximize thevalue of the land.

CONSTRUCTION COSTS

Despite important progress in knowledge and inconstruction methods, underground structures as a rulecost more to construct than equivalent abovegroundstructures. But some combina-tions of geological environment,

scale and type of facility may

provide direct savings inconstruction cost.

It is also to be emphasized thatthe cost and construction timeof underground constructioncontinue to decrease comparedto aboveground construction. But higher design stan-

dards and environmental mitigation costs offset much ofthe cost impacts of the improvements in undergroundconstruction. However, these technological improve-

ments also have led to high levels of safety in under-ground works.

SAVINGS IN SPECIAL DESIGN FEAT U RES

The physical characteristics of underground facilitiesprovide direct cost benefits when compared with a sur-face facility.

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Fig 42 : Washington Metro Tunnel Costs (USA)


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For example, thermal isolation reduces peak loaddemands for a facilitys air conditioning system, enabling

a smaller and thus less expensive system to be installed.

The partial costs for providing low vibration, constanttemperature, or clean room space may also be lessunderground than at the surface.

For aboveground buildings that would require an expen-sive exterior finish, significant savings can be madeunderground where such special design features areu nnec e ss a r y.

EN E R GY SAVINGS

The thermal advantages of underground buildings usual-ly translate into reduced energy costs to operate them.Although ventilation and lighting costs may increase,thermal benefits outweigh these in moderate to severe

cl i m a t e s.

MAINTENANCE COSTS

The physical isolation of underground structures fromthe external environmental effects that deteriorate buil-ding components can result in low maintenance costs for

underground structures.

R E P L A CEM E NT C OST S

Underground structures last significantly longer thantheir surface counterparts. Above-ground structures aregenerally much more susceptible to damage and dete-rioration. Good examples include the numerous railroad

tunnels that have been in service for over 100 years.

TAKING INTO ACCOUNT THE INDIRECT BENEFITS

OF THE UNDERGROUND STRUCTURES

The assessment of underground structures is strongly rela-ted to the community valuation of drawbacks of surface oraerial structures in terms of environmental degradation.

Unfortunately, most of the numerous advantages of under-ground structures, especially those concerning the protec-

tion of the environment, cannot be assessed easily in termsof monetary value.

As a consequence of the mixing of well-defined and poor-ly-defined but important costs and/or benefits, the decisionmaking process concerning the realization of an under-

ground structure (especially when it is compared to anaerial or surface solution) is flawed.

Thus, cost comparisons should not only refer to the well-

defined life-cycle costs, but must take into account thevarious advantages offered by the underground alternative,particularly the environmental benefits.

The International Tunnelling Association is working to helpfind means of quantifying these advantages with the coope-ration of all the professionsconcerned (engineers,

economists, planners,architects, ecologists, etc.).

Fig 43 : Cost comparison betweenhydrocarbon

storage in rock cavernsand in steel tanks

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As demands for underground facilities to be constructedhave increased, risk considerations have taken on ever-

greater importance. In spite of the impressive progressthat has occurred in underground construction during the

last several de-cades, decision-makers still expressa concern for the

risks encountered inu n d e r g r o u n dconstruction, even ifthese risks alsoexist for other types

of construction.

Feasibility studies and, even more important, tendersand contracts, must deal with the following categories of

risks and potential hazards :

Financial risks, such as cost overruns, or lower (thanprojected) rates of capital return ;

Risk that public facilities will not be accepted and usedby the public to the degree anticipated ;

Contractual risks, such as additional work not covered,time delays, disputes and claims ;

Ground conditions, such as unexpected geological or

geomechanical features, overrating of ground reaction tothe excavation, or more water leakage than expected ;

Construction risks, such as tunnel boring machine fai-lures, cutting tools wearing out too fast, face collapses,

or sealing leaks ;

Environmental risks, such as affecting the quality ofground water, damages to the surrounding buildings, air

or noise pollution ;

Risks in operation, notably for transport tunnels.

These factors are of vital importance in order to achie-ve positive attitudes from the public for undergrounds o l u t i o n s .

Within the scope of its general objective: Towards animproved use of underground space , the InternationalTunnelling Association forms international working

Fig 44 : Three-Centered StationShield - Metro ofTokyo (Jap an)

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groups to study and report on specific topics, gatheringa wide range of information from scientific, technical,

planning, statistical, legal, administrative, economic andsocial fields and then evaluates them in order to defi-ne research and development objectives, or simplyspread the results of recommendations to decision-makers and planners.

All these studies relate to one or several of the mainissues examined in this article and are especially aimedat reducing the here above mentioned risks. The resultsof these studies can be found on the website of the

International Tunnelling Association which is

h t t p : / / w w w. i t a - a i t e s . o r g .

Fig 45 : List ofthe ITA WorkingGroups

Fig 46 : Frontpage of theITA website

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The use of underground space can make a significant contribution to solving the major problems experienced inour world today, i.e. to reconcile economic development, the protection of the environment and the quality of life.Putting these solutions into operation depends largely on the use of more and more efficient and sound construc-tion techniques. In this respect, we can never emphasize enough the importance of the role of the various parties

involved in underground construction (planners, owners, engineers, manufacturers and contractors).

Yet, experience shows that, however essential it may be, the progress in techniques is not in itself sufficient to puta better use of underground space into practice, notably in the cities. All users of underground space have noticedthat the occupation of this space is, in fact, done in a quite disorganised manner. Therefore, it would be desirable

if underground space use was taken into account at an early stage when drawing up large scale outline plans forcities and when making major policy decisions in town planning. In this way its intended use could be recorded in

documents dealing with urbanisation at both the local and regional level.

This need has already been focused by some forerunners for a long time. But any definitive solution can probably

not be implemented in the short term, because of the complexity of the related problems. The tunnelling industryis willing to continue to contribute to research and practical solutions which are directed at a more coherent poli-cy for making the best use of underground space.


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Illustrations are published with the courtesy of5: K.Kovari/R.Fechtif, 6: A.Assis, 7: Kees S tiksma -Editor, 8: BK a nd S veBeFo, : Etab lisse ment P ublic d u Grand Louvre, 10: J apa n TunnellingAssoc iation (JTA), 11: RATP, 12: Makkone -Errki, 13: Russia n Aca de my of Sc ientist, 14: Norweg ian Tunnelling Ass oc iation, 15: Sa nta P ark (Finland), 16: Profe ss or Ada chi (J apa n), 17: Unde rground

Developpers Association - Kansas City, 18: JTA, 19: Penti Harala, 20: University of Minnesota, 21: Office of Civilian Radioa ctive Waste Manag ement, 22: Ducoux-Barge , 23: Ray S terling, 24:

GS TT, 25: Memminkanen Cons truction Ltd, 26: Meetkundige Dienst, 27: AlpTransit Go thard a nd Sw iss Tunnelling S ociety, 28: S wiss Tunnelling So ciety, 29: Deutsc he B ahn, 30: Trans-Tokyo B ay

Corporation, 31: Kees Stiksma-Editor, 32: Ra y Sterling, 33: S NCB/SA Tuc Ra il/Eurostation NV, 34: Lesotho HIghland s Water Project, 35: C ity of Helsinki Waterworks, 36: RATP, 37: Pete r

Vand erwa rker, 38: Cofiroute, 39: P arkerings bo lage t, 40: RATP, 41: S EMAPA, 42: ITA, 43: Syver Froise, 44: J TA.


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