Guideiines for the Design of Tunnels
Transcription
Guideiines for the Design of Tunnels
YRE REPORT ~_ Guideiines for the Design of Tunnels ITA Working Group on Genera! Approaches to the Design of Tunnels Abstract-e- This ,e(Grui report bv thr ITA Warkmg- Group On (~eneral .ipproaches to th« Drsuin or Tunnels presents IrllernatlOl1a! desHUl CTround procedures iot tunnels. In most tW1nt'lIzrzç proterts. actiuel» pcructpates In prooiding stabilitv to openmg-. T heretore, t he urnerai approach la the desIgn o! tunnels includes site i.Ilvestl,;;atwns. ground prooines and in-situ mO/uIoTln,;;, as ue]! as he ana/vszs oi stresses and deiormntions, For the latter, the ditierent .tructural desz,;;n models' apolied at present-s-including the obseruationai method-e-are presented. Guidelines lar the structural ol the tunnel Immg and natzonal recommendalzons on .ieuuline ,,,mze! design are aiso gn'en. ft Is hoped that the mlormatlOn herrin, based 011 expertences [rom a unde range of tunnel/mg- provects. uull be -tissemrnated la tunnel designers throughout ihe world. rr 1 , Scope of the Guidelines he International Tunnelling Associauon (ITA) \Vorking Group on General Approaches to the Design , of Tunnels was established in 1978. As its Iirst project, the group developed aquestionnaire aimed at compiling inforrnation about structural design models used in different countries for tunnels eenstrucred prior to 1980. A synopsis of rhe answers to the questionnaire was published bv the International Tunnelling Association in ]982 (ITA ]982). As a continuation of that Iirst report, the working group herein presents guidelines that atternpt to condense the varrous answers from the first report and include additional experiences in the general approaches to the design ol tunnel structures, These guidelines tulfill one of the rnain objectives of the International Tunnelling Associauon, namelv, to disperse intermation on underground use and underground llillllia.;nuctur,esth,roughom the world bv crossing national borders F'l"'Î ,<I language harriers. j hose iruerested in the subject of tunnel design should also consult nuhlished reporisot other ITA work ing groups. e.g, the recent IT,\ report on contractual sharing of risk (see Tijt/ST 3:2) and ITA recommendations on mairnenance of runn-Is (see [:rUST 2:3). Furtherrnore, a number of national ~Hld international organizarions. such as the International Societv on Rock Meeharnes. have published recornmendauons on related subjects, such as field measurernents and laboratorv iesungs lor rock and ground. Some ol these publications and reports are lisred in the Appendix. In tunne llina, most otten the ground acuveiv partir ipates in providinz stahilitv ro the opening. Theretore. the design procedure lor tunnels. as cornpared 10 aboveground -trucrures. is much more dependent on such factors as the SHe SI rnanon. ihe rharacter ist ics, and [he excavarion and support rnerhods used. Recornrnendauons on tunnel design This report IS r diteti 0'11 Heinz Duddeck. Ammateur o! the Approaches m (he Design of ITA Warkmg Group on (;meral Hein: Duddeck, Techrucal Tunnels. Present address: Prof. Braunschusrig, [!mver.\!l1l ol Braunschwezg. Beethouenstrasse 5I. Fed eral Reoublic of (;ermanv. ,,00 {(wl'ullmQ; Pnmed (Hlä Hl (~i(';l.i {'r:JnQ'1'ound Hnt~Hn. SplKt j't-,f!'lmloU;'V, Vol No pp. :"::57-2'i9. 19X~ I Résumè-Le grouoe de tmvazi AITES SUf ie dimensionnemeni des tunnels presente ici .Ion deu xteme rapport. En rassemblant loutes 'lUl rtaient accessibles entre les pa»: :>IU i, :nfol'matuJns, dimens!071nement des tunnels, nous espérons, que les expenences gagnées sur beaucoup de protets des travaux souterrams seron/ propagèes dans tout Ie monde. Parce que Ie sol parucipe d'une grarui» partie à iournir des moyens de stabilitè pour des ouvertures souterrames, des methodes de dlmenszonnement comprennent ausSI hlen les inVestlgatlOns sur Ie chantler. ies essais laboratolTes et la surveIllance pendant Ie progres du travai/ que l'analvse des contramles et des detormations. Concemant ce dernzer ootnt, Jes diitèrents et actuellement ~ppliqués mode/es de dimenswnnement y compris auss! la methode d'obseroation, sont prèsentès, Recommendations oous les details de revêtement et queiou-, recommandatlOns natlOnaies sur Ie dimenswnnement des tunnels achèoent ce rapport. naturaHy are lirnited with regard to their consistencv and applicabilitv because each tunnelling project is àffected by special features that must be considered in the design. Nevertheless, it is hoped that the general outline provided in these guidelines, based on the experience gained hom manv tunnelling projects, may be of sorne help for these staTting a project. 2. Outline of General Approaches 2.1. General Procedure in Designing a Tunnel Planning participation a tunnelling project requires the interdependenof the tollowing disciplines, at a minimum: • • • • Geology. Geotechnical engineering. Excavarion technology. e.g. machine tunnelling. Design of the supporting structural elements. induding; long-term behavier of rnaterials. • Coacracr principles and law, Although the experts in each of these disciplines mav he responsible only for their specific area of know ledge, the decision on the ma in design features should be the outcomeo[ the cooperative iruegration of all the disciplines. Only ihus can it be ensured rhat the project. in all its details, has been developed in unitv, and nor as the consecuuve addition of the separate work of each of the experts. The basics doeurnerus lor tunnel design should inc!udeor cover: • The geologica! report presenting the resu irs ol the geological and geophvsical survey. !lil The hvdrogeological report. t> The geotechnical report on site invesrigarions. including the interpretation of the resu lts of site and laboratory tests wirh respect to the tunnellins; process, soi l and mek classificarion. etc., • Inforrnauon on l ine, cross-secuon. drainage, and structural elements afiecting later use of the tunnel. !lH>«i· 779R SM UGO Pl'f~pmon + Prrs, ,no pa, .. • Plans for and a description of the projeered excavauon or driving procedure. including rhe different cross-secrions reiated to different ground condinons. • Design doeurneuts for the types of excavauon rnethods and tunnel supports likely to he applied, considering, e.g. excavation advance and face support (tvpes and number of anchors. shotcrete strength, closure length, ete. • The program Ior the in-situ monitoring of the tunnel bv field measurernents, • The analvsis of stresses and deforrnations rfor unlined tunnels as wel! as for single-er double-lined tunnels I. and the dirnensioning of the tunnel support for intermediate phases and final linings, • The design tor waterproofing or drainage. • Structural doeurnerus for the Iinal design of the tunnel project. including the detailing, • During and after the excavation, reports on the field measurernents and interpretation of their results with respect to the response of rhe ground and the structural safety of the tunnel. • Doc~mentation of the problems encountered during the excavation and measures applied, e.g. strengthening the ground or changing the projeered type of support. based on monitoring resuits. The above sequence of these basic doeurnenis also provides the general outline of the design procedure. 2.2. Elements of the Structursl Design Model for Tunnels In planning, designing, analvsing and detailing a structure, engineers promise that the structure wiJl neither suffer structurally nor collapse during its projeered lifetirne, Thus, rnodels of the realîry are necessarv for analvsis in order to predier the behaviour of a tunnel during the excavation and during its lifetime, Models are also needed for bidding on projects, The following main elements involved in the design procedure are shown as a flow-chart in Fig. I: (1) Geology and site inuestigations must confirm the line, orientation, depth, etc.. of the opening, e.g. a cavern. (2) Ground probing and soil or rock mechanics must be aoplied to determine the ground characteristics, e.g. primary stresses, soil or rock strength, Iaults, water conditions. 2.3. Different Approaches Basad on Ground Conditions and Tunnelling Methods The response of the ground to extavation of an opening can vary widely. Based on the type of ground in which mnnelling takes place. four principal types of tunneHing may be defined: I) for cut-and-cover tunnelling, in most cases the ground acts only passively as a dead load on a tunnel structure erected like any aboveground engineering structure. (2) In soft ground, immediate support must be provided by a süH !ining (as. for example. in the case of shield-driven tunnels with tubhings for ring support and pressurized slurry Fer N aciual StaUlontv ·lnltnOWO sail/tiV ma1çm F(gure 1. Design process (or tunnelling. 238 Tt·C'.;NELLlNG AND .• )NDERGROUND I Experience end preliminar» estimates or calculations are used to deterrnine the cross-senion required and the choice of the excavation method er the tunnel driving machine to be used, as well as the methods ot dewatering the ground and the selection of the supporting structural elements, (4) After steps IlH3) are completed, the tunnelling engineer must derive, or even invent, a structural model. By applving equilibrium and cornpatibility conditions to the model. the engineer has to arrive at those criteria that are factors in deciding whether or not the design is safe. Different rnodels may be used for each excavation phase, Ior the preliminarv and the Iinal tunnel lining, or for different ground behaviour, e.g. in discontinuous rock or homogeneous soft soil. Modelling of the geometrie features rnav varv greatlv, depending on the desired intensitv of the analvsis. f:;) A safety concept drawn hom failure hypotheses mav be based on criteria such as strains, stresses, deformarion. or Iailure modes. The bypass in Fig. I indicates that for manv underground structures, as in mining or in self-supporting hard rock. no design models at all are applied, In such cases, past experiences alone may he suffierent. Risk assessment by the contractor as well as by the owner is needed at the time of contract negotiarions. Risks involve possible structural failures of the tunnel support and lining, functional Iailures after completion of work, and Iinancial risks. The contractual aspects also include risk sharing and risk responsibilities. In-situ monitoring can be applied only after the tunnelling has begun, If the displacements stop increasing over time. it generall y may be assumed that the structure is designed safe!y. Yet monitoring provides onlv part of the answer to the question of safety, Ior it does nor tell how close rhe structure rnay be to sudden collapse or nonlinear failure modes. The results of field rneasurements and experiences during excavation may com pel the engineer to change the design model by adjusting it to real behaviour, An iterative, step-bv-step approach is characteristic of the design of structures in the ground that ernplov the participating strength of the ground (see loops in Fig. I). The designer may begin by applving estimated and simple behavioural models, Adjustments based on actual experiences during rhe tunnelling excavation (such as excavating the initial sectien in the same ground condinons or driving a pilot tunnel) will bring the model doser to reality and refine ir (if refinement is consistent with the overall accuracy auainable). The interpretations of in-situ measurements (and some back analyses) also rnav assist designers in making these adjustments. All of the elements of the structural design model in Fig. I should be considered an interacting unitv, Scattering of parameters or inaccuracv in one part of the model wiJl affect the accuracv of the model as a whole. Therefore, the Same degree of simplicity or refinemenr should be provided consistentlv through all the elements of the design model. For example, ft is inconsistent to apply very refined mathematical tools simuitaneously with rough guesses of important groundcharaeteristics. SPACE TECHNOLOGY Volume 3, Number 3. 1988 lor tace support). In such a case. the ground usuallv providing resistance Hl outward detorrnauon ot the lining, i. j) In medium-hard rock or in more cohesive soil, the ground mav he streng enough to allow a eertam open secnon at the tunnel face. Here. a eertam amount of stress release may permanentlv he vaiid befere the supporting elements and the lining acting effectively, In th is siruation onlv a fraction the prirnarv ground pressure is acting on the lininz. i. .J:l···When tunnelling in hard rock. ihe alone mav the stabilitv of the opening sa that onlv a th in anv, wil! be necessarv for surface proteetion. The design model must take imo account the rock around the tunnel in order 1O predier and verify safety considerations and deformations. Especiallv in ground condirions that change along the tunnel axis, the ground may he strengthened bv injections. anchoring, draining. freezing, etc. Under these circumstances. case (2) mav he irnproved, at least temporarilv, to case The characteristic stress release at the tunnel face t Erdrnann 1983) is shown in Figs 2 and 3. The relative crown displacement w is pletred along the tunnel axis, where w/wo = l.0 represems the case of an unsupported tunnel. In mediumstift ground nearlv 80%of the deforrnations have already takent place befere the lining (shown here as shotrrete) is stiff enough to participate. O,ll (1,2 ______ ~.L 0,6 <,.0 \llIll1ll!1IlOdol I without / stress '.iRst 0,& 1.0 w, ,wIIMut t w/., il""'!lT-------L--r;;,o- Figure 2. Crown displacement bevond the tunnel face. w along the axis, ahead and »l~Ol olm •• I , -lilt- ,;; I" GoorG~ \> I Fm a simpliiied plane model with na stress release, where the Iull primary siresses are assurned to act on a lined opening, ihe displacement mav be onlv 0.4 of that occurring in the unsupported case. The corresponding stress release is shown in Fig. 3. The simplified example, considering onlv the constant part of radial pressure, yields the values shown for a ring stiffness of EaA = 15.000xO.3 =4500 MN/m and a ground deforrnation modulus of EK = 1000 M:'J/m2• Even in the unrealistic case when the full primary stress acts simultaneousiv on the ground opening and the lining, onlv .">5% of the stress is taken by the Iining: in the case of EBA 2250 MN/m, onlv 38% is taken by the lining. If an open sectien of 0.25 of the tunnel diameter is left without lining support. the iining takes onlv 25%of the primary stresses: Ior Lr = 0.5 D, it takes only 12%of the primary stresses. FOT very soft ground requiring immediate support (as in the case of very shallow tunnels). almest 100%of the primary stresses are acting on the lining, The values change, of course. with other stiffness relationships and other stress distributions than these shown in Fig. 3, with other cross-sections. and other tunnelling methods, 2.4. Site tnvestiqetions; Structursl Analysis end In-Situ Monitoring An adequate intensity of site exploration, from which geological and hydrological mappings and ground profiles are derived, is most important for choosing the appropriate tunnel design and excavation rnethod. A well-documented geological report should provide as much intermation as is obtainable about the physical features along the tunnel axis and in the adjacent ground, The amount of information should be much greater than the inforrnation required Ior entering directly into a structural analvsis. The results of an analysis depend very rnuch on the assurned model and the values of the significant parameters. The main purposes of the structural analvsis are to provide the design engineer with: (I) a better understanding of the ground-structure interaction induced by the tunnelling process; (2) knowledge of what kinds of principal risks are involved and where they are located: and (3) a tooi for interpretating the site observations and the in-situ rneasurements, The available mathematica 1methods of analysis are much more refined than are the properties that constitute the structural model. Hence, in most cases it is more appropriate to investigate alternative possible properties of the model, or even different models, than to aim for a more refined model. FOT most cases. it is preferabie that the structural model ernploved and the parameters chosen Ior the analyses be lower-Iimit cases that may prove that even for unfavourabl« assurnptions, the tunnellieg process and the Iinal tunnel are suffici:ffit!y safe. In general. the structural design model does not trY to represent exactlv the verv actual condinons in the tunnel. although it covers these conditions. In-situ monitoring is important and should he an integral part of the design procedure. especiallv in cases where stahil ity of the tunnel depends on the ground properties. Deformanons and displacemenrs generallvcan he measured with much more accuracv than stresses. The geometrv of the deformanons Figure 3. Ground stresses acttng on the lining as fmetions of Ihè pnmarv stress (Erdmann 1983J. Volume 3. :'Jumber 3. 1988 and their development over time are most significant Ior the interpretanen of the act ual events, However, in-situ moniroring evaluates onlv the verv local and acrua I situatiou in the tunnel. Therefore, in genera I the condinons taken into account bv the design calculations do not coincide with the condinons that are monitored. Only by relaring rneasuremenr results and possible failure modes bv extrapolaring can rhe engineer arrivé at considerations of safety margins. In many cases, exploratorv tunnelling may he rewarding because of the inforrnation it vields on the actual response of the ground to the proposed m~thods for drainage. excavation, TI'NNELLlNG AND UNDERGROt'ND SPACE TECHNOLOGY 239 TBM drivinz. support. etc. In important cases a pilot tunnel mav be driven: such a tunnel mav even be eniarged to the lul! fin~l tunnel cross-secnon in the most representarive ground along the tunnel axis, For Iarger projects, it rnav he useiul to excavate a trial tunnel prior to commencing the actual work, :VIoreintensive In-situ monitoring of the exploratory tunnel sections should check the design approach by numerical anaiysis. 2.5. Design Criteria and Evaluating Structursl Safety An underground structure may lose its serviceabilitv or its structural safety in rhe following cases: The structure loses its watertightness, The deformations are intolerably large. The tunnel is insufficiently durable for its projeered life and use. The material strength of the strucrural elements is exhausted locally, necessitating repair. The support rechnique (for exarnple, in erecting segmental linings) fails or causes damage. Exhaustion of rhe material strength of the system causes structural failure, although the conesponding deformations develop in a restrained manner over time. The tunnel collapses suddenlv because of instability. The structural design model should yield criteria related to' Iailure cases. against which the tunnel should be designed safely. These criteria mav be: • • • • • Deforrnanons and strains. Stresses and utilization of plasticiry. Cross-sectional Iining failure, Failure of ground or rock strength. Limit-analysis Iailure modes. In principle, me safety margins may be chosen differently Ior each of the failure cases lisred above. However, in realitv the evaluauon of me actual safety margins is most complex and very much affected by the scattering of the involved properties of the ground and the structure and, Iurthermore, by the interacting probabilisnc characteristics of these properties. Therefore, the results of any calculation should be subject to crincal refleceion on their relevanee to the actual conditions.' National codes for concrete or steel structures may not always he appropriate for the design of tunnels and the supporting elements, Computational safetyevaluations should alwavs he cornplemented by overall safety considerations and risk assessments employing crincal engineering judgment, which may include the Iollowing aspects: • The ground characteristics should be considered in light of their possible deviauons from average valnes. • The design model itself and the values of parameters shouid he discuseed bv the design team, whieh includes all of the experts involved (see Secnon 2.1. "Ceneral Procedure in Designing a Tunnel," above). • Several and more simp Ie calculation runs with paramerrie variations may uacover rhe scattering of the results. In general. this approach is much more informative than a single over-refined investiganon. • The in-situ measurements should he used for successive adjustment of design models. • Long-term measuremem of ddormations via extrapoiation may reveal lO a large extent the final stabilitv ol the struemre, although sudden collapse may not blO announced in advance. 3. Site Investigations and Ground Probings 3.1. GeoJogical Data and Ground Parameters The appropriate amount of ground investigations on site and in laboratories mav vary considerably from project 1O 2,10 TUNNELLlNG AND I 'NDERGROUND SPAC.E TECHNOLOGY Because the types of ground explorations and probmgs depend on the special features of the tunnelling project. its purpose. excavation rnethod, ere.. thev should he chosen bv the expert team, especially in consultatien with the design engineer. The intensitv of the ground explorations wil] depend on the hornogeneirv of the ground, the purpose of the tunnelling, rhe cost of boring, e.g, for shallow or deep cover. and ether factors. The geological investigations should include the following basic geotechnical information (see also 15RM Commission on Classification of Rocks and Rock Masses 1981). 3.1.1. Tunnels in rock Zoning. The ground should he divided in geotechnical units Ior which the design characteristics mav be considered uniform. However, relevant characteristics rnav displav considerable variations within a geotechnical unit. The Iollowing aspects should be considered Ior the geological descripnon of each zone: • Name of the geological formation in accordance with a genetic ciassification. • Geologie structure and Iracruring of the rock mass with strike and dip orientauons. • Colour, texture and mineral cornposition, • Degree of weathering, Parameters of the rock mass e.g. in five classes of intervals. including: • • • • • • • • • • Thickness of the lavers. Fracture intercept, Rock classification, Core recovery. Uniaxial compressive strength of the rock. derived from laboratory tests. Angle of friction of the fractures (derived from laboratorv direct shear tests). Strength of me ground in on-site situations. Deforrnation properties (modulus). Effect of water on the rock quality. Seismie velocity. Primary stress field of the ground. For larger tunnel projects, tests evaluating the natural stresses in the rock mass may be recommended, For usual tunnel nroierts one shou kl least estimate the stress ratto Oh! Cl" al ruunes ,cve" wnere Oh IS the lateral ground pressure and (1" me major principal stress (usuallv in the vertical direction), Ior which the weight of the overlving rock generally may be taken. Teetonic ssresses should be indicared. Water conditions. Two types of inforrnation about water condinons are required: (I) Permeabilitv, as determined bv: Coefficient k (mis) (from field tests). Lugeon unit (from tests in boreholes), (2) Water pressure: At the tunnel level (hvdraulic head), .tt piezometric levels in bereholes. Deiormabilitv of the rock mass. In-situ tests are required ro derive the two different deformation moduli. which can be determined either from static medlods (dilatometer tests in boreholes. plate tests in auits. or radial jacking tests in chambers) or from dynamic methods (wave velocitv by seismic-refraction or by geophysical logging in borehoies). Engineering judgment should he exercised in ehoosing the \'alue of ,he modulus most appropriate for the design-for instance. oy .he relevant tangent of the pressur,e-dtef(Jrl1naition curve ar the primary stress level in the statie method. Propenieslor which information is needed when tunnel boring machines are to he employed indude: Abrasiveness and hardness. Mineral composites. as, e.~. quartzite contents. Homogeneity. Volume 3. Number 3, 1988 Suielling potential of the rock. The présence of sultates, hvdroxvdes, or minerats should he nvesugated bv rnineraloaical testing. A special odeometer test mar used to deterrnine the swell test-curve of a specimen subjeered first to a load-unload-reload cycle in a dry state. and then unloaded with water. The following ground water conditions should be given: Water levels. piezometric levels. variations over time. pore pressure measurements in confined aquifers. Water chemisuv. Water temperatures, Expected amount of water inflow, 3.1.2. Tunnels in sml The geotechnical description should primarilv follow the recornmendations given above for rock. Additional special features for wil include: 1. Soil identijication (laboratorv testing): • Partiele size distribunon, • Atterberg • • • • Iimits WI' wp' Unit weights. ')I, "Id. 'Yl:. Water content ur. Permeabilitv k. Core recovery. 2. Meehamcal properties determined bv laboratory testing: • Friction angle dru, cP. • Cohesion e", e. • Compressibility Tnt" c.: 3. Meehaniea!:tJroperties deternined bv field testing: • Shear strength Tl' (Vane-test). • Penetration N (Standard Penetrasion Test). • Deformabilitv E (Plate bearing, Dilatometer). 4. Ground water eondition (in addition to these liseed in 3.1.1.): permeability, as determined by pumping tests. value or a value corresponding to a moderately conservative fractile of a Caussian distribution is more appropriate than the worst case value. A set of all the parameters descrihing the ground behaviour of one tunnel sectien with regard 10 tunnelling should he seen as a comprehensive unit and should he well-balanced in relation 10 each ofthe parameters. For example, a small val ue of ground deîormation modulus indicates a tendency 10 plastic behaviour, to which corresponds a ratio of lateral to vertical primarv stress that is closer to LD. Hence, Ior alternative investigations some complete. balanced sets of parameters shouid be chosen instead of considering each parameter alone, unrelated to the ethers, The available rnethods Ior ground prohing and laboratorv tests, their applicabilitv and accuracv are given in the Appendix. 3.3./nterpretation of Test Results end ûocumentetion The field and laboratorv tests should be given in welldoeurnenred reports. in the form of actual results. Based on these reports. an interpretation of the tests that is relevant to the actual tunnelling process and the requirements of the design models for Ihe structural analvsis is necessary. At the time the tests are planned, the team of experts referred to in Sectien 2.1 should decide which ground properties and ground characterisucs are necessary for the general geotechnical descripuon of the ground and for the projeered design model. Thus, a closer relationship mav be achieved belween ground investigations and tunnelling design. and between the amount and refinement of tests and the tunnelling risks. The doeurnerus should lay open the rationat interpretational way in which design values are derived from test results. This method has proven 10 he especially useful in the teadering process, because it condenses the relevant data for the description of the ground and for the design of the tunnel on a band along the tunnel axis beneath a graphical representation of the runnel profile (see the examples in Figs 9-13). 3.2. Evaluation of Parameters by Ground Probing en« Laboratory Tests The properties of the ground that are relevant for the tunnel design should be evaluated as carefully as possible, In-situ tests. which cover larger ground rnasses, generally are more significant than are laboratorv tests on srnall specimens. which often are the better preserved parts of the coring. The natural scattering of ground properties requires an appropriate number of parallel tests-at least three tests for each propertv (see also the cortesponding 15RM recornmendanons l. Results of laboratorv tests must be adjusted to site conditions. The size of specimen, the effects of ground water, the inhomogeneitv of the ground on site. and the effects of scattering must he considered, The conclusions drawn from tests also should take into consideration whether the specimens were taken from distutbed or undisturbed ground. In many cases, the first part of the runnelling may he interprered as a large-seale test, the experiences from which mav he drawn upon not only Ior the subsequent excavations but also Ior prediering ground hehaviour. In certain cases, long horizon tal boreholes may facilitate ground prohing ahead of the face, or a pilot tunnel may serve as a test tunnel that at the same time provides drainage. The on-site investigations provide valuahle resuhs for checkillg the correlation of in-situ tests with laboratorv tests. Special tests correspond directly to the proposed mnnelling method may oe required. e.g. lor the sufficiem preservation of a membrane at the face of a hentonite shield. The evaluation of the parameters should indicate lhe expected scattering. From probabilistic consideratioll of norma!ly dislributed quantities il ean he dedun'd that a mean Volume 3. Number 3. 1988 Such condensed tables may be prepared Iirst for rendering and the preliminarv design. and then improved through experience gained and incoming monitoring results, However, it should be clearlv stated, especiallv in the contract papers. that much relevant information is lost or oversirnplified in such tab les. and that therefore the geotechnical reports and ether complete doeurneuts should be considered the primary doeurneuts. 4. On Structural Design Models for Tunnelling 4.1. Alternative Design Models The ëxcavation of a tunnel changes the prirnarv stress field into a rhree-dimensional pauern at the tunnelling race. Farther from the face. the stress field eventuallv will return to an essentiallv two-dimensional svstern. Therefore, the tunnel design may consider only two-dimensional stress-stram Iields as first approxirnations, The design of a tunnel should take into account the imeraction between ground and lining. In order to do so. the lining must be placed in dosest possible hond with the ground. To preserve Ïts nalural strength. Ihe ground should he kept as undislurbed as possible. The deformations restdting from Ihe tunnelling process (see Fig. 2) reduce lhe primarv ground pressure and create stresses in the iining eorresponding la that fractionai part of the primary stresses in the ground which act on the suslaining lining. The stresses depelld on the stiffness relationship of the ground lO the Iining, as weil as on the shape of the tunnel cross-section. The latter should he selected such that an arching anion in the groundand the !ining may develop. TiiNNELUNGAND UNDERGROl1ND SPACE TECHNOLOGY 2·11 {r.::\2 ' '\.V empirical approach tt t~ . ::1$::1 -'+7-- mn mn Gv IGv=y h rrm rrm Gv Gv Gh~$~ ~m~~m~ ~m~Gh om [[[] om rrrn Figure 4. Alternative plane-strain design models fOT different Figure 4: presents Iour different structural rnodels for a plane-strain design analysis, The cross-secrions need not be circular. These Iour models are explained more explicitly below. In soft ground, irnmediate support is provided by a relativelv stiH lining. For tunnels at shallow depth (as for underground railways in cities) , it is agreed that a twodimensional cross-sectien may be considered, negleering the three-dimensional stress release at the face of the tunnel during excavation. In cases (I) and (2) in Fig. 4, the ground pressures acting on the cross-sectien are assumed to be equal to the prirnarv stresses in the undisturbed ground. Hence, it is assumed that in the final state (some years alter the construction of the tunnel), the ground eventuallv will return to nearly the sarne condition as befere the tunnelling, Changes in ground water levels, traffic vibrations, erc., mav provoke .this "readjustment," In case ( I), for shallow tunnels and soft ground, the full overburden is taken as laad. Hence, no rension bedding is allowed at the crown of the tunnel. The ground reaction is simplified by radial and tangenrial springs, arriving at a bedded-beam model, In case (2), for rnoderatelv stift ground, the soil stiffness is ernploved by assuming a rwo-dirnensional continuurn model and a complete bond between lining and ground. As in case (I l, stress release due to predeformations of the ground is neglected, Inward displacements result in a rednetion of the pressure on the lining, Case assurnes that some stress release is caused deforrnauons that occur befere the lining participates, In medium-hard rock er in highlv cohesive soil, the ground mav be streng enough 10 allow a certain unsupporred section al rhe tunnel face (see Fig. 2). Also, for tunnels having a overburden. a rednetion of the acting crown pressure (represented in Fig. 4 bv h < H) is taken into account. In case 141,the ground stresses acung on the lining are determined bv an empirica! approach, which rnav he based on previousexperiencee wirh the sarne ground and rhe same tunnelling rnethod, on in-situ observations and monitoring 242 Tt';-';7'iE:LUNG ANI) UNDERGROUND SPACE TECHNOI.OGY depths and ground stiitnesses. of initial tunnel sections, 00 interpretation of the observed data, and on continuous improvements of the design model. If a plane model is not justitied-e-as is the case for caverns, for more complicated geometries of underground structures, or for an investigation directly at the tunnelling face-a threedimensional model may be necessary (see Fig. 5). The threedimensional model also may be conceived as consisring of discontinuous masses (block theory) or a continuurn with discrete discontinuous fissures or faults, Q, Figure 5a. Three-dimensional continuum model. Figute 5b. Example of tuio-dimensional finite-element model. 4,2. Continuurn or Discontinuum Model For structural design models such as those in Figs Sa and b, the ground may he modelled as homogeneous or heterogeneous. isotropie or anisotropic: as a (WOdimensional, i.e, allowing some stress release befere the lirnng is acting, or a three-dirnensional stiff medium. The Iining may be modelled either as a beam element with bending stiffness or as a continuurn. Plasticitv, viscosirv, Iracture of the rock, non-Imear srress-strain and deforrnation Volume 3, Nurnber 3, 1988 behaviour, etc., ma. be covered bv special assumptions for material laws. The design criteria are computed by numerical solutions, Frorn rheir origins, the finite-element metbod and the boundarv-element method are basically continuurn methods. Thus, homogeneons media and stress-strara Iields are evaluated best, In general. discontinua such as rock with fissures and faults, and Iailure modes, which are initiared bv local rupsure. shear failure, or full collapse, cannot be covered bv connnuum rnethods. A continuurn or discontinuurn model is appropriate for tunnel structures where theground provides the principal stability of the opening (as in hard rock) or where the geometrical properties of the underground opening can be modelled onlv by numerical analysis, e.g, in the case of dosely spaeed twin tunnels. 4.3. 8edded-Beam Model (Action-Reaction Model) If the stiffness of the ground is smal! compared to the stiffness of the lining, a design model such as that shown in Fig. 6 may be emploved. In such a case, the active ground pressures are represented by given loads and the passive reaction of the ground against deformarions is simulated bv model may he particularl~ constant bedding m~uli. well-suited to the design af linings af shîeld-driven tunnels. As to applicabilitv, the stiffness ratio 13 may be smaller than 200: 1?~ where: 13 = E.R3/E] < 200, E. is the representative deformation stiffness modulus af the ground, R is the radius of the tunnel cross-sectien or its equivalent for non-eireular tunnels, E] is the bending stiffness of the lining, A more correct soletion for the bedding is given by a nonzero stiffness matrix for al! elements with regard to radial and tangendal displacements, However, in most cases and in view of the unavoidable approximations based on the ether assumptions, a simpler approach may be sufficient. Such an approach considers only ~dial (and, eventually, tangential) bedding, negleering the interdependence of radial and tangenrial displacements and beddings, For non-eireular cross-sections, the continuurn solution reveals that bedding may be increased at corner sections of the Iining, with smaller radius of the curvature. The bedded-beam model may be adjusted to more complex cases, e.g, by reducing the crown load in accordance with stress release at the tunnel face (see Fig. 3) or, for deep tunnels, by assuming bedding also at the crown. For articulated effmive hinges in linings the bending rnoments are smaller; the deîormations may be larger, depending on rhe ground stiffness. For hinged linings the limit of f3 given above is aot valid. The analvsis of the bedded beam vields ring farces. bending mo~e~ts, and d~formations as design criteria for the lining. If the lining' rmg IS completely dosed, the bending momems may he considered less important than the ring forces for providing equilibrium (a smaller safety factor may be fb''V·H rt+rJ a ~'f; G"•• --r I 8. Hi 4R \j~~Gh K,,'Gt:Î:tIJ y Kr"conlllt. Gv ",volume w.igll1 radial displ. ground reactien Figure 6. Example of a bedded-beam tunnels. Volume 3, Number 3. 1988 hoop bending momentlll tere.!> model for shaUow w'j"" __ fJI$. usion streu t.!M". E '_i!lwi ••••• l1lld ccntlfwity Figure 7. C haracteristic curves [or the ground and the suppon [or conuergence-coniinement models (Fenner-Pacher c~rves J. justified Ior the bending rnoments). Allowances also may be made for a plastic rotatien capacity of the Iining segrnents. For tunnels with verv pronouneed stress release due to inward deformations, e.g, Ior deep tunnels in rock, a simple approach to d~sign considerations is given by the convergence-confinement model, which is based only on the int~ction of the radial inward dis placement and the support reaenen to ~hesedeforrnations by resisting ring Iorces and the cortesponding outward pressure (see Fig. 7). The primary stresses (Jo in the ground are released with progressive inward displacements. The acting pressure may e~en mcrease when rock joints are opening with larger displacements, In self-supporting rock, the ground characreristic in Fig. 7 meets the w-axis; because the primary stresses are released completely, a supporting lining is not necessary, Befere the supporting memhers are installed. it is unavoidable-c-even desirable-i-raar decompression associated with the predeforrnation Wo will oceur, The stiffness of the lining determines where both curves (characteristic lines) wil! interseet. At this point, equilibrium as weU as compatibilitv condinons are fulfilled. If the ground characteristic is known, e.g., by in-situ monitoring, rhe predeformation Wo and the stiffness of the lining (including its development over time and as tunnelling advances), and even its plastic properties are veI')' de~isive for the actual stresses in the lining, Both curves m Fig. 7 may vary considerably. In its usual analytical form, the convergence-confinement . model assumes constant ground pressure along a circular tunn~llining. Consequently, ü yields only ring Ierces and no bending moments at all. However, ie may be extended to cover ground pressures that vary along the tunnel lining (Cesta 1986). The model mayalso he applied as a first approximation Ior non-~ircular tunnel cross-sections, although the support reaenen curve is dîstinctlv different, e.g. for horseshoe-type cross sections. Therefore. it may he helptul to use the convergence-confinement model in combination with a contimmm model and in-situ rneasurements. ~lth?ugh the convergence-confinement approach is primarily a tooi Ior the interpretation of field rneasurements it also may he applied in support of the empirica! approach: 4.4. Empirical Approach The structural elemems :md the excavation procedure, especially for the preiiminary support of the tunnel, may be selected mainly based on experience and empirical considerations that rdy more on direct observations than on numerical ?llculations. This procedure may be especially reasonahle af experiences from a successful tunnelling project can be applied to a similar. new one yet to he designed. Such a transier of information is justified only when: • The ground conditions, including those of the ground water, are comparable. • The dimensions of the tunnel and ltS cross-sectional shape are similar. • The depths of overburden are approximately the same. TUNNELLING AND UNDERGROVND SPACE TECHNOLOGY 243 • The runnellina methode to he emploved are the same, • In-SItu rnonitorina yields results cornparable to those lor the precedmg tunnelling project. One disadvantage of prolonged application of the empirica! approach is that, lacking an incentive to applv a more appropriate tunnelling design via a consistent safety assessmern, the structure may he designed overconservauvelv. resulting in higher construction costs, The sirnple approach coutributes little to the advancement of rhe state of the art in tunnelling. The ernpirical approach to tunnel design mav also be applied to larger projects in only alightlv changing ground if provision is made (especiallv in the tender) Ior initial experiences to be extrapolated to the subsequent sections along [he tunnel axis. Such a sinration jusrifies a rneasurernent programme that is more intensive for the Iirst sections, in order to gain experience, 4.5. Observational Method By combining analvtical methods with the empirica! approach and the immediate interpretations of in-situ measurernenrs. a tunnelling design procedure that is adjustable as the tunnel excavarion proceeds rnav be applied, In this approach. the field rneasurements of ground movements, displacements and stresses in the Iining are us~d on an ongoing basis to verify or modifv the design of tfie tunnel. More intensivelv instrumented sections at the early stages of the tunnelling provide the data for these procedures. The interpretation of the rneasured data vields insight into the ground behaviour as areaction to the tunneiling procedure. In applving the observational method, the following condinons must be met: • The chosen tunnelling process must be adjustable along the tunnel Iine, • Owner and contractor must agree in advance on comractual arrangements that allow for modifications of the design 00 an ongoing basis during the project. • The field measurements should be interprered on the basis of a suitable analvtical concept relating messurement data to design criteria. • The interpretation of a partienlar instrumented sectien must be used to draw conclusions abour the other sections of the tunnel. Hence, the experiences are restricted to these tunnel sections that are comparable with respect to ground condinons. ground cover. etc. (see Secnon 4.4 "Empirical Approach"). • Field measurement should be provided throughout the entire length of the tunnel in order to check its assurned behaviour. 4.6. Special Design Features Special considerations may he neeessarv if unusual ground behaviour is expected or is caused by ground improvements. Some special design features and considerations arediscussed below. 4.6.1. Ground impl'Ovement techniqu8s Grouting and injections. Intensive groming or injenions of the ground may improve the ground characteristics considered in the design model. Although in most cases grouting is applied only for dosing discominuities in rock or for strengthening soft ground. in both cases the goal is lO achieve better homogeneüy. Drainage anti. compressed air. UsuaHy the ground is stabiiized bv dewatering it and by avoiding inf/ows Ol water. Ground failure may be avoided if the pore water pressure is minimized. The assumed ground characteristics mav be valid only if successful drainage is possible or if water inflow is prevented. as in tunnelling under compressed air. 244 TI':'<NELLlNG AND UNDERGROUND SPACE TECHNOLOGY Ground [reezing, lrnproving the ground bv Ireezing chang-es the ground properties. The time-dependent stress'train behaviour of Irozen ground can be significant. Freezing draws water toward the Iining, causing an increase in water volume and heave at the surface. Conerering on frezen ground delavs the strength development of the concrete. 4.6.2. Unusual ground bahaviour Suielling ground. Stress release due to tunnelling and-er ground water intlux may cause swelling and a corresponding increase in pressure on the lining. In these cases. a circular cross-sectien or at least an invert arch is recommended. The swelling resulting from a chemica! reaction, as in anhvdrid. generally is much more pronounoed than that due to rhe phvsical absorption of water. as in day. Underground erosion. mtning subsidence, and sinhhoies. Tunnelling in ground that is subject to settlements. as in the case of gypsum erosion or mining subsidence, requires special design considerations. A flexible lining that follows the ground movements by utilizing its plastic deformation capacity is more suitable in these cases than is a too-rigid or briule, failure-prone lining, If the ground has sinkhole potentials, a tunnel structure that can be repaired easilv mav he more economical than a structure designed to allow the bridging of the sinkholes, 5. In-Situ Monitoring 5.1. Pur pose of In-Situ Measurements In-situ monitoring during the excavation and at longer intervals after the tunnel is cornpleted should be regarded as an integral part of the design not only for checking the structural safety and the applied design model but also for verifying the basic conception of the response of the ground to tunneiling and the effectiveness of the structural support. The main objectives of in-situ monitoring are: (I) To control the deformations of the tunnel. including securing the open tunnel profile. The tirne-history development of displacernents and convergences mav be considered one safety criterion. although field measurements do not vield the margins the structure can endure before failing. (2) To verify that the appropriate tunnelling method was selected, (3) To control the seulements at the surface. e.g, in order to obtain information on the deforrnation pattem in the ground and on that part of settlements caused by lowering the water level. (4) To measure the development of stresses in the structural rnembers, indicating sufficient strength or the possibility of strength Iailure. (5) To indicate progressive deformations, which require immediate action for ground and support strengthening, To furnish evidence for insurance claims, e.g. by provicling resulls of levelling the settlements at the surface in town areas. 5.2. Monitoring Methods A programme for monitoring the deformations and stresses during the excavation may comprise the followingmeasuremems (see Fig. 8): (I) Levelling the crown (at the least) inside the tunnel as soon as possible. With regard to imerpretation of the data. 2 reveals that often onlv a smal! fraction of the emire crown movemem can be m~nitored because a larger part occurs before the bolt ean be set. For difficult tunneHing, the clistance between two crown readings may be as close as wIS m. LeveHing of thè invert is recommended for rock having sweHing potemials. (2) Convergence readings (in triangular settings; K in Fig. Volume 3. Number 3, 1988 upper outer saencn lining [Dis t . "'SO ... l00ml L L Illt:Th.lll 9,Om'______ readings cease to increase, However, a safety margin against failure-e-especiallv sudden collapse-e-cannot be deduced Irom measurernenr, except bv extrapolation. L ...--14.0m ..•.. leveHing convergences l K grCK.Ind preSlll.G elCtensometer e ringtorces R sliding micrometer SL 8. Example of in-sim monitoring of the tunnel lining, and the surface exceoation, the preiiminarv settlements. 8) should be rhe standard method for earlv information. are easilv applied and are accurate ro within 1 rnm. In a Iew cross-secuons, the linings mav he equipped with stress cells for reading the ground pressures and ring Iorces in the lining (G and R in Fig. 8). (4) Stress cells also should he installed in a tew sections of the final secoud lining if long-term readings are desired alter the tunnel has been compieeed. (5) Surface levelling along the tunnel axis and perpendicular to ir vield settlements and the correlation to measurements inside me tunnel (see Fig. 2). (6) Extensometers. inclinometers, gliding micrometers rnav he installed from the surface wel! ahead of the tunnelling face.• vielding deformarion measurements within me ground (see Fig. 8). Monitoring of the ground deformations is especially appropriate for checking and interpreting the design model, Therefore, [he installation should he combined with convergence readings and stress cells in the same 6. Guidelines for me Structural Detaiiing of the üning On design aspects with regard to maintenance the reader is relerred to other recommendations of the ITA (see T&UST 2:3). For concrete linings, [he following structural specifications are suggested, I) The thickness of a secend Iining of cast-in-place concrete rnay have a lower limit of 25-30 cm to avoid concrete placing problerns such as undercompaction or honevcombing of concrete. The following lower limits mav he recornmended: -20 cm, if lining is unreinforced: -25 cm, if lining is reinforeed. -30 cm for watertight concrete. (2) Reinforcemem mav be desirabie for crack control. even when it is not required Ior covering inner stresses. On the other hand, reinforcemem mav cause concrete-placing problerns or long-term durabiliry problerns due to steel corrosion. If reinforcement in the secend lining is provided for crack control. a closely-spaced steel rnesh reinforcement rnav have the following cross-secrions in both directions: • At the outer surface. at least 1.5 cm-/m of steel; • At the inner surface. at least 3.0 cm-/m of steel. (3) The recommended minimum cover of reinforcement is: cross-sectien. 3.0 cm The frequencv of [he readings depends on how Iar frorn the tunnelling face the measurements are taken, and on the results. For exarnple, readings may he performed initiallv two times a dav: then be reduced to one reading per week Iour diameters behind theface: and end with one reading per month if the time-data curves justifv this reduction in measuremem readings. 5.3. Interpreting Resutts of In-Situ Monitoring The results of in-situ monitoring should be interprered with regard to the excavation steps, the structural support work, and the structural design model in conjunction with safety considerations. The actual readings normallv show a broad scatter of values, Expectations of reliabrlity may not be met. especiallv for pressure cells, beeause stresses and strains are verv local characteristics. Detormauon and con vergen ce readings are more reliablv obtainable because displacements register integtals along a larger sectien of the ground, The in-situ measurements should be interprered in consideration of the Iollowing: lID The results should verify whether the tunnelling method is appropriate. Grapbed time-historv charts may reveal a decreasing rate of deformauon. or unoover danger of coltapse. • Large discrepancies between rhe theoretically prediered and actuallv observed deformauons may force revision of model. However, measurements are valid onlv Ior the acmal state at ehe time and the place where thev are taken. Long-term influences such as rising water level. traffk vibrations, and long-term neep are not re~rislere~during excavation. • readings mav promote visual understanding of the strucmral behavior of groun<.!and support imeraction. •• The readings may cover ooly a fraction Ol the acmal phenomena if bolts and stress cells are installed too late lID (see Fig. 2). lID The tunnel may he considered Volume 3, :\lumber 3. 1988 stabie when all the 5.0 cm-6.0 cm 4.0 cm-5.0 cm 5.0 cm At the outer surface if a waterproof membrane is provided, At the outer surface if it is directly in contact with the ground and ground water. At the inner tunnel surface. For the tunnel invert andwhere water is aggressive, (4) For lining segments, specificauons (I), (2) and (3) above are nor valid, especially if the segrnented tunnel ring is the outer preliminary Iining. For detailing the tunnel segments, special attention should be given to avoiding damage during transport and erection, (5) Sealing against water (waterproofing sheets) may be necessarv under the following conditions: • When aggressive water action threatens to damage concrete and steel. lID When the water pressure level is more than 15 m above the Clown. When there is a possibilirv of freezing of ingressing water along the tunnel secnon close to the portals. • Wnen the inner installations of the tunnel must be lID proteered. (6) In achieving watertighmess of concrete. special specifications of the concrete mixture, avoidanee of shrinkage stresses and temperarare gradients during setting, and the Iinal quality of the concrete are much more important than theoretica I cornputarions of crack widths . Temperature effects (tension stresses) may be somewhat controlled by working joints (as close as 5 mat the portals) and by additional surface reinforcemem in concrete exposed to low temperatures, (8) An initial lining of shotcrete may he considered to participate in provi.ding stabi.Iitv of the tunnel only when the long-term durability of the shotcrete is preservecÎ. Requiremems for achieving long-termdurability indude the absence of aggressi.ve water. the limitalion of concrete additives for acce!erating the seuing (Iiquid accelerators), and avoiding shotcrete shadows behind steel arches and reinforcements. TlTNNELLING AND UNDERGROt'ND 'sPACE TECHNOLOGY 245 I eonsolîclGtion I '_ I 10 11,,, '~ i cf the tunnel rI 1 I grCMQ 1 =:i j~ (l:UGht, ,itNt 1 <:=mf'Oi pol.t_ i i1 I1 eonvetgenee I I Of ~ •••••••• $ •• ..... a •••• ..... - , .• Wltion ~ •• : # -, " anisoll'OPY II I ' f .AH H zcne deeompressed I nismmollY I 1! j roek tl!fl'lll4ll"ature ! I stre_ witllin I Ihe wall adaPlÎOll of roek I round I aboul lhe lunneI . Figure 9. Table of measured data end encountered conditions along a tunnel in Eranee. HttigM Uo.,. c.. -.----Horth. Hannow.r legend: : QUO." Oty ust = IIPOO" N't 2 1'f'Jk!cn. ls' :: \OW- 115 J 1: ,,"thout inv .• " Technica! design eonditions tor the Hopfenberg - Tunnel (TVR) (Fed. RGermany) longiiudinal sectien with design characteristics Figure 10. Predieeed ground conditions, tunnelling classes and design characteristics along a tunnel of the rapid railuiav line in GeTmany. 246 TUN'NELUNG AND UNDERGROUND SPACE TECHNOLOGY Volume 3; Number 3, 1988 <00•• He ig nt Ni: Sands!one' t mudstCh! aJtern3tmn Si: mudmolW' F : fault .tone- I fII ,?O '200 '1>' , 100 I 41kQ Ki IQ rJ'll"ter Geolog.e.l <HUt 500 600: For mat ron i N';:Nishiyama 800 Formation .ag 42u 200 400 fiOO?(JO 200.00 600 Si: Shitva Forma t I on 800 5.5. Seism.e Veloei IJ W.ler 44lua 209 il(M) 11Kl' :.DJ AOf) Ni Rock ""me Unconltned Compr"""vo (Compe renee Facter ) ,(::- and m.s. (s.p.) 2.0-2.2 -.=52-56't./ { 4.5-4.8 ~Ireoglh i • I i I t Ie Inflow Rock CI •• s IS IL 11. IN Squeezing NOl. Pr-oper-ty a.s.: s an ds tone m.s.:muds tone LR:sandstone predominates Figure 11. Predicted ground conditions along a tunnel line iexemple submiued by [apen). Figure 12. Documentation of geology, ground classes. support, geotech nicaliield measurements gathered duringa tunnel project in Austria. Volume 3. Nurnber 3. 1988 TC:'\:--:ELUNG AND UNDERGROUND SPACE TECHNOLOGY 247 7. Exampies of Presentation of Tunnel Design Data Figures 9-12 are national exarnples of tabuiated intermation on geotechnical condinons and design characteristics given in condensed farm along a longitudinal tunnel sectien. This inforrnation mav be part of the rendering documents and should be amended with ongoing tunnelling, By gatbering the data actuallv encountered along the tunnel line in a sirnilar table, a comnarison can he made between prediered and actual tunnelling conditions, 0 Nota Referencas Erdrnann. J. !983•.Comparison of rhree-dirnensional Braunschweig, West Cermanv: Berichte Instuut fur Statik. Technica! Universitv of Braunschweig. Gesta, P. 1986. Recommendations Ior use of the ronveraenceconfinemem rnethod. Tunnels Ouurages SouterrainS 73: 18-39. International Society of Rock Mechanica Commission on Classiticauon of Rocks and Rock Masses, 1981. Int. j. Rock stechanics Mining Sci. 18: 85-110. International Society of Rock Mechanics, 1975. ISRM Recornrnendauons on site invesrigation techniques, International Tunnelling Association Worki.ng Croup on Structural Design of Tunnels. 1982. Advances Tunnell. Technol. Subsurface Use 2(3): 153-228. of rwo-dimensional and development desig-n rnethods Ior tunnels un Oermam. 'See, tor exarnple, the Swiss SlA Dokument 260 or the corresponding C.S.-ASCE Code. , on Structural Appendix. International and Natienel Recommendations Design of Tunnels. Although the Iollowing selected list of recommendations by national and intemational organizations is not complete, it neeertheless should provide the reader with sourees of additional inforrnation regarding the design of tunnels. OrganizationiCountry Pubheation International Tunnelling Views on structural design models for tunnelling. Adoances in Tunnelling Association (ITA), Technology and Subsurface Use 2:3 (1982). International Society for Rock Meeharnes (ISRM) ISRM recommendations on site investigation techniques, July 1975. ISRM Committee on Field Tests: Document No. l-Suggested Metbod for Determining Shear Strength Document No. 2-Suggested Methods Ior Rock Bolt Tesung ISRM Commiuee on Laboratory Tests; ISRM ComJnittee on Suielling Rocks: Document No, I-Suggesteà Methods for Determining the Uniaxial Compressive Strength of Rock Matenals and Point Load Strength Index. Document No. 2-Suggested Porosity, Density, Absorption Durability Index Properties. Methods for Determining Water Content. and Related Properties. Swelling and Slake Australian Standard 1726 - S.A.A. Site Investigation Code, Austral ia Australian Standard 1289 - Methods of Testing Soils for Engineering Purposes. Austria ÖNORM E 2203 Untertagebaunorm, Werkvertragsnorm. Richtlinien und Vertragsbeseimmungen, Projektierungsrichtlinien für Oeotechnische Forschungsges, Srassenwesen, Nov. 1977. Federal Republic of Germany (in Cermarn Arbeiten, RVS 9.240 u. 9.241, Reeommendations Ior rhe design of underground openings in rock. TunnelbauTeschenbucn 1980, Gluckaui-Verlag, Essen (1980), pp. 157-239. Recornmendations for the analvsis of Tunnels in soft ground (980), Bautechnik 10 (980), Berlin, pp, 349-356. Recommendations Ior the Concrete Lining of Tunnels in soft ground (986). Bautechnik 10 (986), Berlin, pp, 331-338. Tunnels et Ouoreges Souterrains, Special Issue July 1982, pp, 32-123; France Rêflexions sur les methodes usuelles de calcul du revêtement des souterrains (Usual calculation methods Ior the design of tunnel linings). 248 TVNNELUNG ANO !JNDERGROPND SP.\CE TECHNOLOGY Volume 3. Nurnber 3, 1988 Prèsentation de la mèthode de construction des tunnel avec sourènernent immediat par bèton projetè et boulonnage (Presentation of the tunnel construction method with imrnediate support by shotcrete and bolting). Recomrnandarions SUf les condinons d'emploi du boulonnage (Recommendations for condinons of the use of bolting). Tunnels et Ouurages Souterrains 73 (jan.zFeb. 1986), pp. Recommendations Ior use of the convergence-confinemem method, 18-38: Tunnels et Ouurages Souterrains 67 (jan.z Feb. 1985), pp. 32-43: Recommandations relatives au choix d'un type de soutenement en galerie (Recornmendations Ior the selection of tunnel support). Tunnels et Ouutages (1984), pp, 80-97: Recommandations relativa à l'ernploi des citres dans ia construction des ouvrages souterrains (Recommendations on the use of steel arches as temporatv support in tunnel structures). Japan Tunnel Engineering Committee, Japan Society of Civil Engineering, Japan Tunnelling Association Standard Specificatiens for Tunnels: Mountain Tunnelling Shield Tunnelling Metbod. Nov. 1986. Method. J une 1986. Cut-aud-eover Method. june 1986. Switzerland Recommandation SlA No. 199: Etude du massif rocheux pour les travaux souterrains. 1975. (Also in German) Norme SlA No. 198:Travaux souterrains (avancement à l'explosif), 1975. (Also in German) Recommandation SlA No. 198/1: Construction de tunnels et de galeries en roeher-au moven de tunneliers, 1985. (Also in German) U nited Kingdom British Standard 1377. Methods of test for soils Ior civil engineering purposes. British Standards Insritution, 1975. British Standard 5930, Code of Praenee Ior site invesugations, Institution, 1981. British Standards Craig, R. N. and Muir Wood, A. M. A review of tunnel lining praenee inthe Unired Kingdorn. TRRL Supplementary Report 335, 1978. Tunnelling Waterproofing. CIRIA Report 81,1979. Dumbleton, M. J. and West, G. A guide to site investigation tunnels. TRRL Laberatory Report 740,1976. Unieed States of Amenca American Society of Civil Engineers (ASCE) Volume 3, Number 3, 1988 procedures for Guidelines fOT Tunnel Lining Design. Ed. by T. O'Rourke. ASCE Technica] Committee on Tunnel Lining Design, Teehuical Council on Research. TUNNELLlNG AND UNDERGROUND SPACE TECHNOLOGY 249