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Small fractures in deep sea sediments: indicators of pore fluid migration along compaction faults
378A in small steps, with immediate support by shotcrete, mesh, and anchors. As geology varied constantly, continuous engineering geological supervision was necessary. Working operations were controlled by deformation movements. 906450 Tunnelling problems in the young Himalayas Madan, M M Tunn Tannlg V22, N5, May 1990, P55-61
examined. Site investigation using pilot drifts, core logging, cyclic water testing, and monitoring borehole diameter is described. Interpretation of the retrieved data and application to design of support in squeezing or flowing ground is discussed. Most Himalayan tunnels are excavated by drill and blast, but NATM after pre-support drainage and grouting or forepoling is better adaptable to squeezing ground.
Tunnelling conditions in the Himalayas vary from soft, running, squeezing ground to tough and massive rocks. Many areas have extensive faulting, shear and thrust zones. Tunnelling methods are diverse and matched to specific geologies. Problems caused by rock conditions and equipment/personnel are listed. The Indian experience is summarised with reference to a number of completed and current projects.
906454 Influence of the faults on the stability of underground openings Tao Zhen-Yu; Zhao Zhen-Yin Proc International Symposium on Underground Engineering, New Delhi, 14-17 April 1988 I/1, P321-324. Publ Rotterdam: A A Balkema, 1988
906451 The method of subsidence prediction by means of influence functions - including results of case studies Schumann, E H R; Hamenstadt, R Proc Symposium on Advances in Rock Mechanics in Underground Coal Mining, Witbank, 12 Sept 1989 P91-100. Publ Marshal#own: SANGORM, 1989
Faults located near underground openings have a tendency to decrease the strength of the surrounding rock and influence the stress distribution. In order to understand the influence of the faults on the stability of the underground openings, both the development of stress patterns and the deformation behaviour of the rock around the underground opening must be analysed. A geomechanical model design to enable the study of the influence of faults on underground openings is presented.
In order to predict surface subsidence arising as a result of total extraction mining, different techniques have been developed. Numerous empirical influence functions and influence functions based on physical principles according to the theory of elasticity have been formulated. The underlying principles of two types of influence function methods, the 'linear' (elastic) model and the empirical stochastic model, are discussed. The inherent limitations of both models and the range of their successful applications are critically assessed. Case studies based on South African collieries are also presented. 906452 Small fractures in deep sea sediments: indicators of pore fluid migration along compaction faults Buckley, D E Proc Conference on Disposal of Radioactive Waste in Seabed Sediments, Oxford, 20-21 September 1988 Pl15-135. Publ London: Graham and Trotman, 1989 (Advances in Underwater Technology, Ocean Science and Offshore Engineering, V18) A long piston core from the South Nares Abyssal Plain intersected four fractures in plastic sediments at depths 17-25m below sea floor. Seismic studies also indicated faults in this area. All fractures were in oxidised brown clays. Selective chemical tests in sediments surrounding the fractures showed 70% of reducible Mn and 40% of reducible Fe had been leached from the alteration halo surrounding the fracture plane, suggesting reducing pore fluids had migrated along the plane. This suggests that compaction faults may act as episodic conduits for vertical advection of pore water during dewatering of unconsolidated sediments. This must be considered when assessing effectiveness of sediment barriers for radioactive waste disposal. 906453 Investigation for design of tunnel supports for tunneling in Himalayas Ram, V Proc International Symposium on Underground Engineering, New Della', 14-17 April 1988 VI, P291-295. Publ Rotterdam: A A Balkema, 1988 Himalayan rock masses are unpredictable and inhomogeneous, and systematic site investigation and project planning are required for tunnelling. Case histories and their problems are
Stresses around underground openings See also: 906289, 906323
906455 Illustration of the importance of soil nonlinearity in soilstructure interaction problems Fourie, A B; Beer, G Comput Geotech V8, N3, 1989, P219-241 Measured and predicted performance of a shallow buried steel pipe in sand under surface surcharge are compared. Three failure criteria were used to model soil behaviour: Mohr-Coulomb and inscribed and circumscribed Drucker-Prager. Even at low surcharge loads, hoop stresses and bending moments were significantly influenced by the constitutive law assumed. Neglecting possibility of soil yield and considering it solely as an elastic continuum can lead to invalid estimation of pipeline stresses.
906456 Sudden excavation of a long circular tunnel in elastic ground. Technical note Carter, J P; Booker, J R lnt J Rock Mech Min Sci V27, N2, April 1990, P129-132 Excavation of underground structures in stressed rock masses releases some stored strain energy. The speed of release affects subsequent behaviour of the rock masses. In some metalliferous mines and civil works,the surface area generated by excavation is generated almost instantaneously, and it is appropriate to model excavation as application of a set of tractions over the boundaries of the structure. This is examined for the case of a cylindrical cavity. The solution is developed in terms of Laplace transforms of the field quantities, and inversion of the transforms is carried out numerically. Influence of excavation rate on transient stress fields is also examined.
© 1990 Pergamon Press pie. Reproduction not permitted
examined. Site investigation using pilot drifts, core logging, cyclic water testing, and monitoring borehole diameter is described. Interpretation of the retrieved data and application to design of support in squeezing or flowing ground is discussed. Most Himalayan tunnels are excavated by drill and blast, but NATM after pre-support drainage and grouting or forepoling is better adaptable to squeezing ground.
Tunnelling conditions in the Himalayas vary from soft, running, squeezing ground to tough and massive rocks. Many areas have extensive faulting, shear and thrust zones. Tunnelling methods are diverse and matched to specific geologies. Problems caused by rock conditions and equipment/personnel are listed. The Indian experience is summarised with reference to a number of completed and current projects.
906454 Influence of the faults on the stability of underground openings Tao Zhen-Yu; Zhao Zhen-Yin Proc International Symposium on Underground Engineering, New Delhi, 14-17 April 1988 I/1, P321-324. Publ Rotterdam: A A Balkema, 1988
906451 The method of subsidence prediction by means of influence functions - including results of case studies Schumann, E H R; Hamenstadt, R Proc Symposium on Advances in Rock Mechanics in Underground Coal Mining, Witbank, 12 Sept 1989 P91-100. Publ Marshal#own: SANGORM, 1989
Faults located near underground openings have a tendency to decrease the strength of the surrounding rock and influence the stress distribution. In order to understand the influence of the faults on the stability of the underground openings, both the development of stress patterns and the deformation behaviour of the rock around the underground opening must be analysed. A geomechanical model design to enable the study of the influence of faults on underground openings is presented.
In order to predict surface subsidence arising as a result of total extraction mining, different techniques have been developed. Numerous empirical influence functions and influence functions based on physical principles according to the theory of elasticity have been formulated. The underlying principles of two types of influence function methods, the 'linear' (elastic) model and the empirical stochastic model, are discussed. The inherent limitations of both models and the range of their successful applications are critically assessed. Case studies based on South African collieries are also presented. 906452 Small fractures in deep sea sediments: indicators of pore fluid migration along compaction faults Buckley, D E Proc Conference on Disposal of Radioactive Waste in Seabed Sediments, Oxford, 20-21 September 1988 Pl15-135. Publ London: Graham and Trotman, 1989 (Advances in Underwater Technology, Ocean Science and Offshore Engineering, V18) A long piston core from the South Nares Abyssal Plain intersected four fractures in plastic sediments at depths 17-25m below sea floor. Seismic studies also indicated faults in this area. All fractures were in oxidised brown clays. Selective chemical tests in sediments surrounding the fractures showed 70% of reducible Mn and 40% of reducible Fe had been leached from the alteration halo surrounding the fracture plane, suggesting reducing pore fluids had migrated along the plane. This suggests that compaction faults may act as episodic conduits for vertical advection of pore water during dewatering of unconsolidated sediments. This must be considered when assessing effectiveness of sediment barriers for radioactive waste disposal. 906453 Investigation for design of tunnel supports for tunneling in Himalayas Ram, V Proc International Symposium on Underground Engineering, New Della', 14-17 April 1988 VI, P291-295. Publ Rotterdam: A A Balkema, 1988 Himalayan rock masses are unpredictable and inhomogeneous, and systematic site investigation and project planning are required for tunnelling. Case histories and their problems are
Stresses around underground openings See also: 906289, 906323
906455 Illustration of the importance of soil nonlinearity in soilstructure interaction problems Fourie, A B; Beer, G Comput Geotech V8, N3, 1989, P219-241 Measured and predicted performance of a shallow buried steel pipe in sand under surface surcharge are compared. Three failure criteria were used to model soil behaviour: Mohr-Coulomb and inscribed and circumscribed Drucker-Prager. Even at low surcharge loads, hoop stresses and bending moments were significantly influenced by the constitutive law assumed. Neglecting possibility of soil yield and considering it solely as an elastic continuum can lead to invalid estimation of pipeline stresses.
906456 Sudden excavation of a long circular tunnel in elastic ground. Technical note Carter, J P; Booker, J R lnt J Rock Mech Min Sci V27, N2, April 1990, P129-132 Excavation of underground structures in stressed rock masses releases some stored strain energy. The speed of release affects subsequent behaviour of the rock masses. In some metalliferous mines and civil works,the surface area generated by excavation is generated almost instantaneously, and it is appropriate to model excavation as application of a set of tractions over the boundaries of the structure. This is examined for the case of a cylindrical cavity. The solution is developed in terms of Laplace transforms of the field quantities, and inversion of the transforms is carried out numerically. Influence of excavation rate on transient stress fields is also examined.
© 1990 Pergamon Press pie. Reproduction not permitted