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Understanding mechanisms of failure
128A cavern operation has been modelled using computer codes FLAC, UDEC, and JOBFEM. In situ stress and cavern shape have major influences on the joint displacement. The required properties of the rock mass to maintain integrity of the cavern lining are assessed.
922432 Evaluation of pressures and deformations for underground openings Prabhakar, B; Kulkarni, S S; Painthakar, A G Proc Indian Geotecknical Conference, 1989, Geotechniques of Problematic Soils and Rocks, Visakbapatnam, 14-16 December 1989 VI, P387-391. Publ New Delhi: Sarita Prakashan, 1989 Analytical and numerical methods suitable for study of stress and deformation fields around underground openings are examined. Closed form analytical techniques are considered first. These become difficult to apply in cases of complicated shape or anisotropic or discontinuous geologic media. In these more complex conditions, numerical techniques such as finite element analysis, finite difference method, boundary element analysis, or the combined finite element-boundary approach are applied. Relative merits of the numerical techniques are discussed.
Underground excavation failure mechanisms 922433 Understanding mechanisms of failure Sofianos, A I Tunn Tunnig V23, N9, Sept 1991, P17-18 A collapse in a tunnel in Alpine mountain series rocks caused serious delay to the project. Failure occurred at overburden depth about 90m, with lateral pressure coefficient about 1.5. The failure occurred over a length of about 58m, where the top heading was driven some way ahead and the bench lowering had just been completed. The failure region was in water beating clay schist, which caused squeezing conditions. Extra support and backfill were used to prevent total collapse. Remedial measures included mesh shotcrete, bolts, and ribs, plus grouting of the surrounding rock mass. Drainage may reduce the problem.
Tunnels See also: 922314 922435 Vertical clearance modification of two railroad tunnels Ott, K R Bull ,4ssoc Engng Geol I:28, N2. May 1991, PI83-192 To accommodate modern rolling stock, it was necessary to remove 0.6m of rock from the crown of the 100 year old Haverstraw and Kingston tunnels in New York State. The tunnels are in hard, jointed diabase and folded massive sandstone and limestone respectively. A physical condition and geotechnical mapping survey of the tunnels was first carried out. Potential block failure modes were identified. Although the tunnels have stood virtually unsupported, the planned excavation will cause fracturing and increase the loosened zone. Rock dowel support and mesh where necessary are specified. Excavation is by smooth blasting. 922436 World's longest single TBM drive Darling, P Tann Tuanlg V23, N9, Sept 1991, P21-23 The 14.5kin long, 2.5m diameter Dhiarizos water diversion tunnel is under construction in Cyprus. It runs through Lafkara and Pakhna formation sedimentary rocks. Lafkara rocks are soft to medium strength (UCS 10-80MPa), Pakhna rocks are laminated horizontal strata, chalk marls, and sandy limestone, overall strength 10-18MPa. Four fault zones are encountered. Progress to date is 7.4kin, with 1400m in bad ground. Primary support is Swellex bolts and shotcrete in bad ground, secondary support includes expansion shell rock bolts, arches, mesh and more shotcrete. 922437 Blasting for a straighter route McWilliam, F Tunn Tuanlg V23, Ng, Sept 1991, P32-34 The construction of the 4820m Puymorens tunnel in the eastern Pyrenees is described. Excavation is on four faces simultaneously. Support is according to ground conditions: minimal in massive schistose granite (50ram of shotcrete and occasional bolts); 100ram of fibre shotcrete plus five 3.5m resin grouted bolts/m of tunnel in hard schists; increasing density of bolts, arches, and shotcrete thickness in altered and heavily fractured schist; and 250ram of shotcrete and arches in a fault zone. Final lining will be cast-in-situ concrete, providing a 9.6m wide, 5m high opening. Excavation procedures are described and progress reported.
922434 Design for rehabilitation of a concrete lined shaft damaged by plastic deformation Burke, J; James, J V Proc I S R M International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10-12 September 1990 P63-71. Publ Rotterdam: ,4 ,4 Balkema, 1990
922438 Importance of support stiffness in deep tunnels Snee, C P M Proc Tunnelling '91, London, 14-18 April 1991 P101-107. Publ London: Elsevier, 1991
A study was carried out in order to prevent interruptions in the shaft operations due to deformations of weak volcanic rock at the Western Areas Gold Mine. The rock mass deformation behaviour was assessed through observation of the hangingwall, geotechnical boreholes, and excavations intersecting the rockmass. Based on these results, a computer simulation model was built. Results from this model have been used to design remedial measures. The shaft pillar has been enlarged by restricting mining operations, partial filling at certain levels carried out, and the shaft lining redesigned.
The Selby Complex in North Yorkshire includes 10 shafts sunk to depths 400-1000m. At inset level the dominant strata are siltstone with mudstone at the tunnel crown. Excessive closure of unlined drifts was observed. It was proposed that this could be overcome and the load on the inset lining reduced by increasing the stiffness of the support in the unlined drifts. Field measurements and observations confirm this. The use of rock bolts in the unlined tunnels will lower the requirements for steel arches and thickness of the final concrete lining of the tunnels.
© 1992 Pergamon Press Ltd. Reproduction not permitted
922432 Evaluation of pressures and deformations for underground openings Prabhakar, B; Kulkarni, S S; Painthakar, A G Proc Indian Geotecknical Conference, 1989, Geotechniques of Problematic Soils and Rocks, Visakbapatnam, 14-16 December 1989 VI, P387-391. Publ New Delhi: Sarita Prakashan, 1989 Analytical and numerical methods suitable for study of stress and deformation fields around underground openings are examined. Closed form analytical techniques are considered first. These become difficult to apply in cases of complicated shape or anisotropic or discontinuous geologic media. In these more complex conditions, numerical techniques such as finite element analysis, finite difference method, boundary element analysis, or the combined finite element-boundary approach are applied. Relative merits of the numerical techniques are discussed.
Underground excavation failure mechanisms 922433 Understanding mechanisms of failure Sofianos, A I Tunn Tunnig V23, N9, Sept 1991, P17-18 A collapse in a tunnel in Alpine mountain series rocks caused serious delay to the project. Failure occurred at overburden depth about 90m, with lateral pressure coefficient about 1.5. The failure occurred over a length of about 58m, where the top heading was driven some way ahead and the bench lowering had just been completed. The failure region was in water beating clay schist, which caused squeezing conditions. Extra support and backfill were used to prevent total collapse. Remedial measures included mesh shotcrete, bolts, and ribs, plus grouting of the surrounding rock mass. Drainage may reduce the problem.
Tunnels See also: 922314 922435 Vertical clearance modification of two railroad tunnels Ott, K R Bull ,4ssoc Engng Geol I:28, N2. May 1991, PI83-192 To accommodate modern rolling stock, it was necessary to remove 0.6m of rock from the crown of the 100 year old Haverstraw and Kingston tunnels in New York State. The tunnels are in hard, jointed diabase and folded massive sandstone and limestone respectively. A physical condition and geotechnical mapping survey of the tunnels was first carried out. Potential block failure modes were identified. Although the tunnels have stood virtually unsupported, the planned excavation will cause fracturing and increase the loosened zone. Rock dowel support and mesh where necessary are specified. Excavation is by smooth blasting. 922436 World's longest single TBM drive Darling, P Tann Tuanlg V23, N9, Sept 1991, P21-23 The 14.5kin long, 2.5m diameter Dhiarizos water diversion tunnel is under construction in Cyprus. It runs through Lafkara and Pakhna formation sedimentary rocks. Lafkara rocks are soft to medium strength (UCS 10-80MPa), Pakhna rocks are laminated horizontal strata, chalk marls, and sandy limestone, overall strength 10-18MPa. Four fault zones are encountered. Progress to date is 7.4kin, with 1400m in bad ground. Primary support is Swellex bolts and shotcrete in bad ground, secondary support includes expansion shell rock bolts, arches, mesh and more shotcrete. 922437 Blasting for a straighter route McWilliam, F Tunn Tuanlg V23, Ng, Sept 1991, P32-34 The construction of the 4820m Puymorens tunnel in the eastern Pyrenees is described. Excavation is on four faces simultaneously. Support is according to ground conditions: minimal in massive schistose granite (50ram of shotcrete and occasional bolts); 100ram of fibre shotcrete plus five 3.5m resin grouted bolts/m of tunnel in hard schists; increasing density of bolts, arches, and shotcrete thickness in altered and heavily fractured schist; and 250ram of shotcrete and arches in a fault zone. Final lining will be cast-in-situ concrete, providing a 9.6m wide, 5m high opening. Excavation procedures are described and progress reported.
922434 Design for rehabilitation of a concrete lined shaft damaged by plastic deformation Burke, J; James, J V Proc I S R M International Symposium on Static and Dynamic Considerations in Rock Engineering, Swaziland, 10-12 September 1990 P63-71. Publ Rotterdam: ,4 ,4 Balkema, 1990
922438 Importance of support stiffness in deep tunnels Snee, C P M Proc Tunnelling '91, London, 14-18 April 1991 P101-107. Publ London: Elsevier, 1991
A study was carried out in order to prevent interruptions in the shaft operations due to deformations of weak volcanic rock at the Western Areas Gold Mine. The rock mass deformation behaviour was assessed through observation of the hangingwall, geotechnical boreholes, and excavations intersecting the rockmass. Based on these results, a computer simulation model was built. Results from this model have been used to design remedial measures. The shaft pillar has been enlarged by restricting mining operations, partial filling at certain levels carried out, and the shaft lining redesigned.
The Selby Complex in North Yorkshire includes 10 shafts sunk to depths 400-1000m. At inset level the dominant strata are siltstone with mudstone at the tunnel crown. Excessive closure of unlined drifts was observed. It was proposed that this could be overcome and the load on the inset lining reduced by increasing the stiffness of the support in the unlined drifts. Field measurements and observations confirm this. The use of rock bolts in the unlined tunnels will lower the requirements for steel arches and thickness of the final concrete lining of the tunnels.
© 1992 Pergamon Press Ltd. Reproduction not permitted