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Tieback anchors support record setting walls for Super Collider experimental halls in Texas
124A
REINFORCEMENT:DIRECT ROCK SUPPORT METHODS
953150 Tieback anchors support record setting walls for Super Comder experimental halls in Texas B. Schmidt & D. T. Mocller, in: Tannellling and ground conditions. Prec. congress, Cairo, 1994, ed M.E.A. Salam, (Balkema), 1994, pp 273-279. The Superconducting Super Collider particle accelerator is currently under construction near Dallas, Texas, USA. As part of this project, large sophisticated pieces of equipment will detect and measure subatomic particles resulting from high energy, proton-proton collisions, These detectors will be housed in large underground halls up to 69 m deep, founded in competent Austin Chalk. The walls, mostly in the weaker Taylor Marl, are permanently supported by tiebacks, and the roof is permanently supported by columns. This paper presents the design concepts and analyses for the halls. (Authors)
953151 Suction force below plate anchors in soft clay B. M. Das, E. C. Shin, R. N. Dass & M. T. Omar, Marine Georesources & Geotechnology, 12(1), 1994, pp 71-81. The results of a number of laboratory model tests for the short-term ultimate uplift capacity of a circular plate anchor embedded in saturated soft kaolinite and montmorillonite are presented. The tests were conducted with and without venting the bottom of the plate anchor in order to determine the variation of the suction force with embedment ratio. The variation of the suction force is presented in terms of the undrained shear strength of the clay and also the net ultimate uplift capacity. (Authors)
Shotcrete 953152 Effects of development of shotcrete stiffness on stresses and displacements of single and doable tunnels E. Solimau, H. Duddeck & H. Ahrens, in: Tunnelling and ground conditions. Prec. congress, Cairo, 1994, ed M.E.A. Salam, (Balkema), 1994, pp 549-556. Tunnel construction applying the shotcrete method consists of two shells. The first has to act as a primary or temporary support during the building time. The second one is considered as the final support. The primary tunnel support is designed to carry 100% of the primary stresses of the ground. It is formed by shotcrete, steel ribs or lattice arches and welded wire meshes. The paper shows the results of the three dimensional analysis of single and double tube tunnels taking into consideration the nonlinear change of the shotcrete stiffness with time. The results are presented in diagrams that show the relative changes in stress and deformations, in comparison with the case of constant shoterete stiffness. (from Authors)
953153 Numerical modelling of shotcrete and concrete tunnel finings G. Swoboda & A. Moussa, in: Tunnelling and ground conditions. Prec. congress, Cairo, 1994, ed M.E.A. Salam, (Balkema), 1994, pp 427-436. In this paper the authors attempt to give a realistic simulation of the partial excavations used in NATM which produce incremental loading on the shotcrete lining with the progress of excavation with time, while the shoterete strength is increasing. The model takes into consideration nonlinearity, cracking, plastic deformation history, and the time dependent strength of shoterete. A practical application of the model in the analysis of a subway tunnel with a double lining system is shown. The finite element coupled with boundary elements are used. A special six nodded beam element is used to model
both shotcrete and final linings. An interface element is produced to model the possible relative deformation between the two linings. Material nonlinearity and cracking of concrete are considered. (Authors)
Direct rock support methods 953154 MuRiple entry pillar stability assessment using the limit equifibrium method T. Unlu & D. J. Reddish, International Journal of Rock Mechanics & Mining Sciences, 31(5), 1994, pp 429-438. The paper introduces the basic concepts of coal pillar behaviour in relation to pillar geometry and cover load with an emphasis on pillars in deep UK coal mining conditions. Results from three dimensional physical models are presented to illustrate the three zones within a heavily loaded pillar proposed by Barren. A limit equilibrium model, based upon Barton's principles but including a number of important modifications, is described. A Windows-based computer package, based upon the model, is developed capable of dealing with multiple openings in square, rectangular and rib pillar combinations with a longwall abutment along one side. (from Authors)
953155 Analysis of compressible axially loaded piles in rock J. K. Kodikara & I. W. Johnston, International Journal for Numerical & Analytical Methods in Geomechanics, 18(6), 1994, pp 427-437. Analytical solutions are developed for the prediction of the load-settlement response of a compressible axially loaded cast in situ pile in rock. The principal input parameters are derived from the ~-z curve which applies to the contact zone between the pile shaft and the embedment material. For larger diameter piles in rocks, these ¢-z curves can differ markedly from curves that apply to piles in clay and may include a significant strain hardening region prior to reaching peak strength. In addition to the complete analyses which would normally require the use of a computer, simplified solutions suitable for hand calculations have been derived for the peak load and the pile head displacement to peak. An example of the application of these simplified design calculations is presented. (Authors)
953156 Behaviour of spliced piles - a field study B. G. Rao, M. P. Jain & G. Ranjan, in: Prediction versus performance in geotechnical engineering. Prec. symposium, Bangkok, 1992, ed A.S. Balasubramaniam & & others, (Balkema), 1994, pp 27-44. In several situations use of long piles becomes necessary. The inconvenience of long piles can be offset by using spliced piles provided the splices/joints between segments do not introduce weaknesses. Four types of joints have been developed, and their performance evaluated through the use of RCC precast piles installed in loose to medium dense cohesionless, and soft clay deposits. The results obtained from their field behaviour both during driving and in situ load testing have demonstrated thdr suitability with respect to performance under compressive, pullout and lateral loads. With a view to eliminating/reducing the negative drag on piles, the ambient soft clay around the piles was transformed into composite mass of low compressibility by resorting to ground treatment techniques utilizing Plain Granular Piles (PGP), Mini Grouted Piles (MGP) and Self Setting Soil Slurry Piles (SSSSP). Adoption of these techniques resulted in significant reduction in settlement of ambient ground and consequently the negative drag on piles. The introduction of bitumen slip layer also resulted in significant reduction of negative drag on piles. It is concluded that the performance of splices
REINFORCEMENT:DIRECT ROCK SUPPORT METHODS
953150 Tieback anchors support record setting walls for Super Comder experimental halls in Texas B. Schmidt & D. T. Mocller, in: Tannellling and ground conditions. Prec. congress, Cairo, 1994, ed M.E.A. Salam, (Balkema), 1994, pp 273-279. The Superconducting Super Collider particle accelerator is currently under construction near Dallas, Texas, USA. As part of this project, large sophisticated pieces of equipment will detect and measure subatomic particles resulting from high energy, proton-proton collisions, These detectors will be housed in large underground halls up to 69 m deep, founded in competent Austin Chalk. The walls, mostly in the weaker Taylor Marl, are permanently supported by tiebacks, and the roof is permanently supported by columns. This paper presents the design concepts and analyses for the halls. (Authors)
953151 Suction force below plate anchors in soft clay B. M. Das, E. C. Shin, R. N. Dass & M. T. Omar, Marine Georesources & Geotechnology, 12(1), 1994, pp 71-81. The results of a number of laboratory model tests for the short-term ultimate uplift capacity of a circular plate anchor embedded in saturated soft kaolinite and montmorillonite are presented. The tests were conducted with and without venting the bottom of the plate anchor in order to determine the variation of the suction force with embedment ratio. The variation of the suction force is presented in terms of the undrained shear strength of the clay and also the net ultimate uplift capacity. (Authors)
Shotcrete 953152 Effects of development of shotcrete stiffness on stresses and displacements of single and doable tunnels E. Solimau, H. Duddeck & H. Ahrens, in: Tunnelling and ground conditions. Prec. congress, Cairo, 1994, ed M.E.A. Salam, (Balkema), 1994, pp 549-556. Tunnel construction applying the shotcrete method consists of two shells. The first has to act as a primary or temporary support during the building time. The second one is considered as the final support. The primary tunnel support is designed to carry 100% of the primary stresses of the ground. It is formed by shotcrete, steel ribs or lattice arches and welded wire meshes. The paper shows the results of the three dimensional analysis of single and double tube tunnels taking into consideration the nonlinear change of the shotcrete stiffness with time. The results are presented in diagrams that show the relative changes in stress and deformations, in comparison with the case of constant shoterete stiffness. (from Authors)
953153 Numerical modelling of shotcrete and concrete tunnel finings G. Swoboda & A. Moussa, in: Tunnelling and ground conditions. Prec. congress, Cairo, 1994, ed M.E.A. Salam, (Balkema), 1994, pp 427-436. In this paper the authors attempt to give a realistic simulation of the partial excavations used in NATM which produce incremental loading on the shotcrete lining with the progress of excavation with time, while the shoterete strength is increasing. The model takes into consideration nonlinearity, cracking, plastic deformation history, and the time dependent strength of shoterete. A practical application of the model in the analysis of a subway tunnel with a double lining system is shown. The finite element coupled with boundary elements are used. A special six nodded beam element is used to model
both shotcrete and final linings. An interface element is produced to model the possible relative deformation between the two linings. Material nonlinearity and cracking of concrete are considered. (Authors)
Direct rock support methods 953154 MuRiple entry pillar stability assessment using the limit equifibrium method T. Unlu & D. J. Reddish, International Journal of Rock Mechanics & Mining Sciences, 31(5), 1994, pp 429-438. The paper introduces the basic concepts of coal pillar behaviour in relation to pillar geometry and cover load with an emphasis on pillars in deep UK coal mining conditions. Results from three dimensional physical models are presented to illustrate the three zones within a heavily loaded pillar proposed by Barren. A limit equilibrium model, based upon Barton's principles but including a number of important modifications, is described. A Windows-based computer package, based upon the model, is developed capable of dealing with multiple openings in square, rectangular and rib pillar combinations with a longwall abutment along one side. (from Authors)
953155 Analysis of compressible axially loaded piles in rock J. K. Kodikara & I. W. Johnston, International Journal for Numerical & Analytical Methods in Geomechanics, 18(6), 1994, pp 427-437. Analytical solutions are developed for the prediction of the load-settlement response of a compressible axially loaded cast in situ pile in rock. The principal input parameters are derived from the ~-z curve which applies to the contact zone between the pile shaft and the embedment material. For larger diameter piles in rocks, these ¢-z curves can differ markedly from curves that apply to piles in clay and may include a significant strain hardening region prior to reaching peak strength. In addition to the complete analyses which would normally require the use of a computer, simplified solutions suitable for hand calculations have been derived for the peak load and the pile head displacement to peak. An example of the application of these simplified design calculations is presented. (Authors)
953156 Behaviour of spliced piles - a field study B. G. Rao, M. P. Jain & G. Ranjan, in: Prediction versus performance in geotechnical engineering. Prec. symposium, Bangkok, 1992, ed A.S. Balasubramaniam & & others, (Balkema), 1994, pp 27-44. In several situations use of long piles becomes necessary. The inconvenience of long piles can be offset by using spliced piles provided the splices/joints between segments do not introduce weaknesses. Four types of joints have been developed, and their performance evaluated through the use of RCC precast piles installed in loose to medium dense cohesionless, and soft clay deposits. The results obtained from their field behaviour both during driving and in situ load testing have demonstrated thdr suitability with respect to performance under compressive, pullout and lateral loads. With a view to eliminating/reducing the negative drag on piles, the ambient soft clay around the piles was transformed into composite mass of low compressibility by resorting to ground treatment techniques utilizing Plain Granular Piles (PGP), Mini Grouted Piles (MGP) and Self Setting Soil Slurry Piles (SSSSP). Adoption of these techniques resulted in significant reduction in settlement of ambient ground and consequently the negative drag on piles. The introduction of bitumen slip layer also resulted in significant reduction of negative drag on piles. It is concluded that the performance of splices