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Non-linear viscoplastic creep of rock surrounding an underground excavation
166A
UNDERGROUND EXCAVATIONS :TUNNELS
tiation of partial failure mechanisms in the structure under strong seismic loading. -from Authors
UNDERGROUND EXCAVATIONS 943368 Rock mechanics in the 1990s: large underground facilities ed B. C. Haimson, International Journal of Rock Mechanics and Mining Sciences, 30(7), 1993, pp 1503-1526. These papers were originally presented at the 34th US Symposium on Rock Mechanics, June 1993. Six papers resent the following topics: flow testing of a cement orehole seal; strain rate and heterogeneity influence on moduli and strenlgth of welded tuff; deformation measurements in excavauon disturbed zones; gas barrier design; 3 D structural analysis; and effect of cavern numbers on underground oil storage. -R.Gower
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943369 Efficient mesh generation procedures for finite element analysis of u n d e r g r o u n d structures M. W. F. Grabinsky & J. H. Curran, lnternan'onalJournal of Rock Mechanics & Mining Sciences, 30(6), 1993, pp 591-600. The efficiency and accuracy of the finite element method is del~endent on the volume mesh developed for analysis. Thls can be particularly significant for 3-D analyses of unbounded problems such as underground structures. Several developments in automatic mesh generation have been made in recent years and are increasingly found in commercially available software, although these programs target mainly mechanical engineering applications. The work described in this paper considers application of advanced mesh generation techniques to the analysis of underground structures. The functionality of the software used is described, and some general considerations for mesh development are given. Application of the software is then demonstrated using two mining and two civil engineering structures. -from Authors
Geological factors of importance in underground excavations 943370 Aspectos geoiogicos y geotecnicos replacionados con el proyecto y construccion del Camino Longitudinal Austral, regiones X y XI (Geological and geotechnical aspects of Camino Longitudinal Austral, regions X and XI, Chile) A. Hauser Y., Boletin - Servicio Nacional de Geologia y Mineria, Chile, 43, 1993, 75 pp. This Bulletin deals with the characteristics of the project design, construction, operation and conservation of the Camino Longitudinal Austral (CLA), planned in 1971 and started in 1976. Towards the end of 1992, ca. 2200 km of road had been constructed. The conceptualization strategy, design, evaluation and the materialization of the work had to face strong limitations due to a series of regional characteristics such as poor accessibility, roughness of the relief, high pluviosity, existence of numerous torrential rivers and broad ice fields, all of which affected adversely the supplies and the scarce economic, social and labor development in the region. On the whole, the design limitations and road construction were related to geotechnieal anisotropy parameters, such as, low bearing capacity, high comp.ressibility and poor superficial and internal drainage conditions, presence of expansive soils, high sensitivity to hydric erosion and high absolute slumps, high content of organic matter, local instability in cut slopes; shallow or superficial phreatic levels, resistance to ripping and lack of local borrow materials. -from English summary 943371 Rock roof stability in the sandstone caves of Nottingham A. C. Waltham & I. E. Chorlton, in: The engineering geology of weak rock. Proc. conference, Leeds, 1990, ed J.C. Cripps & others, (Balkema; Engineering Geology Special Publication, 8), 1993, pp 489-492. Hundreds of old artificial caves lie in the sandstone
beneath the city of Nottingham and create significant problems during urban reconstruction. Rock roofs over the caves are mostly I-5 metres thick, spanning voids mostly 2-5 metres wide. The Triassic sandstone is weak, with unconfined compressive strength generally 4-30 MPa; it is friable and easily excavated. However, it is massive with little jointing and indistinct bedding, so that when dry it is strong m compression; when loaded over a cave it fails as a flared plug. Physical models, made of plaster at a linear scale of 1:50, have been loaded to destruction, and initial results suggest that caves with more than three or four metres of rock cover have satisfactory surface stability under load. Local practices in the design of foundations over the caves may be unnecessarily conservative. -Authors
Stresses around underground openings 943372 Non-linear viscoplastic creep of rock surrounding an u n d e r g r o u n d excavation D. Song, International Journal of Rock Mechanics & Mining Sciences, 30(6), 1993, pp 653-658. The shearing viscosity in the plastic region is a non-linear function of shearing stress, normal compressive stress and lapse of time. Through the computations of allowing for the effect of normal compressive stress and omitting the effect, the development of the viscoplastic region and shear deformation m the viscoplastic surrounding rock will be reduced because of allowing for the effect of normal compressive stress, which makes the shearing viscosity in the plastic region ~rcater than a high level. The FEM of initial viscoplastic incremental strain is proven to be effective for the computation and analysis of the non-linear viscoplastic creep in tunnel engineering. -Author 943373 Application of bifurcation theory to rock mechanics problems I. Vardoulakis & J. Sulem, in: Comprehensive rock engineering. Vol. 1, ed J.A. Hudson, (Pergamon), 1993, pp 575-609. This chapter deals largely with the stability of deep underground openings. The general rate boundary value problem is formulated and the mathematical background of equilibritma bifurcation theory is presented. The constitutive models used are given, and two types of bifurcation mode for laboratory testing are given: discontinuous or Iocalised modes; and continuous or diffuse modes. Asymmetric bifurcation modes in triaxial compression of rocks, including shape and size effects arc discussed. Finally a borehole problem is addressed as a typical example of instability observed in underground openings. -R.Gower
Tunnels 943374 Options for tunnelling 1993. Proceedings of an international congress, Amsterdam, The Netherlands, April 1993 ed H. Burger, (Elsevier; Developments in Geotechnical Engineering, 74), ISBN (hardback) 0 444 89935 9, price price US$82.75 (Dfl 320.00), 1993, 916 pp. The choice between several tunnelling options provided the major theme of this conference. This choice is influenced by environment, location, ground and ground water conditions, construction costs, and timing. Other themes highlighted include research and new develo~pments in soft ground and rock. The 77 papers are split into five main sections: general, subjects; soft g r o u n d tunnelling (comparative case studies, cut and cover methods and immersed and submerged floating tunnels, and underground methods); rock runnels (TBM driven, and conventional driven); research and development; and financing and risk allocation in tunnelling. -from Publisher
UNDERGROUND EXCAVATIONS :TUNNELS
tiation of partial failure mechanisms in the structure under strong seismic loading. -from Authors
UNDERGROUND EXCAVATIONS 943368 Rock mechanics in the 1990s: large underground facilities ed B. C. Haimson, International Journal of Rock Mechanics and Mining Sciences, 30(7), 1993, pp 1503-1526. These papers were originally presented at the 34th US Symposium on Rock Mechanics, June 1993. Six papers resent the following topics: flow testing of a cement orehole seal; strain rate and heterogeneity influence on moduli and strenlgth of welded tuff; deformation measurements in excavauon disturbed zones; gas barrier design; 3 D structural analysis; and effect of cavern numbers on underground oil storage. -R.Gower
g
943369 Efficient mesh generation procedures for finite element analysis of u n d e r g r o u n d structures M. W. F. Grabinsky & J. H. Curran, lnternan'onalJournal of Rock Mechanics & Mining Sciences, 30(6), 1993, pp 591-600. The efficiency and accuracy of the finite element method is del~endent on the volume mesh developed for analysis. Thls can be particularly significant for 3-D analyses of unbounded problems such as underground structures. Several developments in automatic mesh generation have been made in recent years and are increasingly found in commercially available software, although these programs target mainly mechanical engineering applications. The work described in this paper considers application of advanced mesh generation techniques to the analysis of underground structures. The functionality of the software used is described, and some general considerations for mesh development are given. Application of the software is then demonstrated using two mining and two civil engineering structures. -from Authors
Geological factors of importance in underground excavations 943370 Aspectos geoiogicos y geotecnicos replacionados con el proyecto y construccion del Camino Longitudinal Austral, regiones X y XI (Geological and geotechnical aspects of Camino Longitudinal Austral, regions X and XI, Chile) A. Hauser Y., Boletin - Servicio Nacional de Geologia y Mineria, Chile, 43, 1993, 75 pp. This Bulletin deals with the characteristics of the project design, construction, operation and conservation of the Camino Longitudinal Austral (CLA), planned in 1971 and started in 1976. Towards the end of 1992, ca. 2200 km of road had been constructed. The conceptualization strategy, design, evaluation and the materialization of the work had to face strong limitations due to a series of regional characteristics such as poor accessibility, roughness of the relief, high pluviosity, existence of numerous torrential rivers and broad ice fields, all of which affected adversely the supplies and the scarce economic, social and labor development in the region. On the whole, the design limitations and road construction were related to geotechnieal anisotropy parameters, such as, low bearing capacity, high comp.ressibility and poor superficial and internal drainage conditions, presence of expansive soils, high sensitivity to hydric erosion and high absolute slumps, high content of organic matter, local instability in cut slopes; shallow or superficial phreatic levels, resistance to ripping and lack of local borrow materials. -from English summary 943371 Rock roof stability in the sandstone caves of Nottingham A. C. Waltham & I. E. Chorlton, in: The engineering geology of weak rock. Proc. conference, Leeds, 1990, ed J.C. Cripps & others, (Balkema; Engineering Geology Special Publication, 8), 1993, pp 489-492. Hundreds of old artificial caves lie in the sandstone
beneath the city of Nottingham and create significant problems during urban reconstruction. Rock roofs over the caves are mostly I-5 metres thick, spanning voids mostly 2-5 metres wide. The Triassic sandstone is weak, with unconfined compressive strength generally 4-30 MPa; it is friable and easily excavated. However, it is massive with little jointing and indistinct bedding, so that when dry it is strong m compression; when loaded over a cave it fails as a flared plug. Physical models, made of plaster at a linear scale of 1:50, have been loaded to destruction, and initial results suggest that caves with more than three or four metres of rock cover have satisfactory surface stability under load. Local practices in the design of foundations over the caves may be unnecessarily conservative. -Authors
Stresses around underground openings 943372 Non-linear viscoplastic creep of rock surrounding an u n d e r g r o u n d excavation D. Song, International Journal of Rock Mechanics & Mining Sciences, 30(6), 1993, pp 653-658. The shearing viscosity in the plastic region is a non-linear function of shearing stress, normal compressive stress and lapse of time. Through the computations of allowing for the effect of normal compressive stress and omitting the effect, the development of the viscoplastic region and shear deformation m the viscoplastic surrounding rock will be reduced because of allowing for the effect of normal compressive stress, which makes the shearing viscosity in the plastic region ~rcater than a high level. The FEM of initial viscoplastic incremental strain is proven to be effective for the computation and analysis of the non-linear viscoplastic creep in tunnel engineering. -Author 943373 Application of bifurcation theory to rock mechanics problems I. Vardoulakis & J. Sulem, in: Comprehensive rock engineering. Vol. 1, ed J.A. Hudson, (Pergamon), 1993, pp 575-609. This chapter deals largely with the stability of deep underground openings. The general rate boundary value problem is formulated and the mathematical background of equilibritma bifurcation theory is presented. The constitutive models used are given, and two types of bifurcation mode for laboratory testing are given: discontinuous or Iocalised modes; and continuous or diffuse modes. Asymmetric bifurcation modes in triaxial compression of rocks, including shape and size effects arc discussed. Finally a borehole problem is addressed as a typical example of instability observed in underground openings. -R.Gower
Tunnels 943374 Options for tunnelling 1993. Proceedings of an international congress, Amsterdam, The Netherlands, April 1993 ed H. Burger, (Elsevier; Developments in Geotechnical Engineering, 74), ISBN (hardback) 0 444 89935 9, price price US$82.75 (Dfl 320.00), 1993, 916 pp. The choice between several tunnelling options provided the major theme of this conference. This choice is influenced by environment, location, ground and ground water conditions, construction costs, and timing. Other themes highlighted include research and new develo~pments in soft ground and rock. The 77 papers are split into five main sections: general, subjects; soft g r o u n d tunnelling (comparative case studies, cut and cover methods and immersed and submerged floating tunnels, and underground methods); rock runnels (TBM driven, and conventional driven); research and development; and financing and risk allocation in tunnelling. -from Publisher