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Performance of deep wellbores in rock with a confining pressure-dependent elastic modulus
158A 893416 Stability analysis of surrounding rock of underground plant in high in-situ stress region in China and some relevant questions Liu-Shi Huang Proc Symposium on Rock Mechanics and Power Plants, Madrid, 12-16 Sept 1988 VI. P209-215. Publ Rotterdam. A .4 Balkema. 1988 Stability of surrounding rocks is a problem for underground excavation in areas with high in situ stress. Data from several such projects in China were collected to determine the constitutive law of the surrounding rock. The effect of in situ stress on stability is outlined, and the influence of rock mass properties, such as discontinuities, elastic modulus, Poisson's ratio and strength index, discussed. A loading method for in situ stress determination is introduced. Factors considered in design of underground structures in areas of high in situ stress are discussed. In China, careful excavation, with rock bohing and use of shotcrete, has been successful.
and (4) uniaxial compression testing. The influence of the threaded rods, drillholes and grout, and width:height ratio of pillars is discussed. Results show that 2 well grouted steel rods significantly increase uniaxial compressive strength, mainly due to the high confining stress provided by the rods as they are tensioned under the transverse strain of the pillar. 893420 Observations, research, and recent results about failure mechanisms around single galleries (In French) Maury, V Proc 6th International Conference on Rock Mechanics, Montreal, 30 Aug-lO Sept 1987 V2, Pl119-1128. Publ Rotterdam: A A Balkema. 1987
893417 Influence of soil surroundings upon the loads of pipes Petrik, P M; Leitner, F Proc ECONMIG 86, Stuttgart, 16-18 September 1986 V2. 7P. Publ Stuttgart: Unieersity of Stuttgart. 1986
Failures of isolated underground structures under simple loadings have been studied. The inability of Mohr-Coulomb type failure criteria to quantitatively predict failure is evident, but they may be able to identify failure modes. Abilities of plastic and elastic theories are examined. Failure initiation is probably inside the wall. Propagation may be by tensile or shear mechanisms, the former probably being more common than was previously realised, The collected work of members of the ISRM Commission on Failure Mechanisms around Underground Openings was the basis of this analysis.
Finite element analysis has been used in a parametric study of the stress and strain fields around flexible and rigid buried pipes. Time dependent behaviour of pipe materials was considered where applicable. Soft and stiff clays, loose and compacted sands, and stabilised backfill soils arc considered. 10 computational algorithms and 5 element types were used. A small selection of the many rcsuhs obtained is illustrated.
89342 I Underground observation of high propagation-rate extension fractures Ortlepp, W D; Moore, M A Proc 6th International Conference on Rock Mechanics, Montreal, 30 Aug-10 Sept 1987 V2. P1173-1180. Publ Rotterdam." A A Balkema, 1987
893418 Space and time variation of microevent parameters occurring in front of an active stope Cichowicz, A: Green, R W E; Van Zyl Brink, A; Grobler, P: Mountfort, P I Proc 2nd International Symposium of Rockbursts and Seism&ity in Mines, Minneapolis, 8-10 June 1988 P213-222. Publ Minneapolis: Unirersity of" Minnesota, 1988
Photographic records of unusual fracture surfaces in the fine grained carbonaceous shale roof of a South African coal mine have been examined. Certain textural features, in particular mirror-zones, suggest very high fracture front propagation rates, up to around 200m/s. Mechanics of the failure have been studied. Gravitational forces alone are seen to be inadequate to cause the failure. Buckling of thinly laminated plates is considered to be the most likely failure mechanism.
Mining operations give rise to a large number of seismic events. A monitoring system was installed 200m ahead of an operational stope. An online numerical program was developed to estimate the seismic moment, seismic energy, corner frequency, static and dynamic stress drop, Q-coda and degree of polarization of microevents. The first 5 parameters describe the seismic source and the last 2 quantify the rock properties. An analysis of the coda signals has shown that the rock mass ~ithin 20m of the stope contains a large proportion of fractured rock. Part of the effort was directed towards investigating variations of the stress drops, Q-coda of the S-wave and the degree of polarization of the P-wave, which could be rockburst precursors. Auth.
893422 Preventative supporting measures to control typical collapse situations in tunnelling (In German) Pacher, F; Vavrovsky, G M Proc 6th International Conference on Rock Mechanics, Montreal, 30 Aug-10 Sept 1987 V2, P1187-1190. Publ Rotterdam. A A Balkema, 1987
Underground excavation failure mechanisms 893419 Reinforcing concrete model pillars with grouted rock bolts Ringwald, J P; Brawner, C O Min Sci Technol V8, NI, Jan 1989, P31-47 Experiments were undertaken to study the improvement in strength and stability of a model pillar due to installation of grouted rock bolts perpendicular to the vertical axis. Theory of failure of a pillar and the effect of the bolt are first outlined. The laboratory test procedure comprised: (1) material testing for sand, reinforcing steel and grout; (2) sample preparation from sand and Portland cement; (3) sample reinforcement;
Failures away from the lace in tunnels are often caused by overloading of the shotcrete lining because of loss of strength and load carrying capacity of the rock mass. It is essential to be able to distinguish between these conditions and less harmful stress redistributions. This can be achieved by careful initial investigation and continuing monitoring of performance.
893423 Performance of deep wellbores in rock with a confining pressure-dependent elastic modulus Santarelli, F J; Brown, E T Proc 6th International Conference on Rock Mechanics,
Atontreal, 30 Aug-10 Sept 1987 V2, P1217-1222. Publ Rotterdam: A A Balkema, 1987 A complete closed form solution is presented for the stresses and displacements induced around an axisymmetric wellbore in rock whose elastic modulus is a function of the minimum principal stress or confining pressure. The theory, which is a generalization of classic linear, constant modulus elastic theory, provides satisfactory explanations of the displacements
¢~ 1989 Pergamon Press plc. Reproduction not permitted
159A and apparent strength enhancement recorded at the walls of model wellbores. An important ramification of the theory is the prediction of a failure pattern in which fractures parallel to the borehole wall may initiate some distance inside the surrounding rock. Auth.
lining-rock interaction methods using models of linear-viscoelastic, linear-elastic linear viscous, and linear elastic non-linear viscous rock behaviour. Calculations of lining pressures show that the former tends to underestimate compared with the latter. Auth.
893424 Mechanical stability of the linkage in deep underground coal gasification (In French) Schmitt, N; Nguyen Minh, D Proe 6tk International Conference on Rock Mechanics,
893428 Design and construction of a shallow tunnel with large span in an urban area Wittke, W
Montreal, 30 Aug-lO Sept 1987 V2, P1223-1226. Publ Rotterdam: A A Balkema, 1987 The linkage tunnel in underground coal gasification must withstand high temperatures (800-1000 deg K) and pressures. The mechanical stability of such a tunnel has been examined using small scale model tests. Mechanical properties of the coal, a non-swelling anthracite, were first measured. Convergence curves were determined under simulated in situ conditions. Results were analysed and a stability criterion proposed. 893425 Seismic activity in a flooded Saskatchewan potash mine Gendzwill, O J; Prugger, A F Proc 2nd International Symposium of Rockbursts and
Seismicity in Mines, Minneapolis, 8-10 June 1988 PI39-148. Publ Minneapolis: Unirersity of Minnesota, 1988 Usually failure in potash mines is due to stress changes associated with subsidence over mined out areas. Failure in a Saskatchewan potash mine which intersected an aquifer, which led to seepage, is described. Initially inflow was controlled by grouting and roof support, but eventually the mine was closed. Soon after, a series of microseismie events occurred, culminating in a magnitude 2.7 earthquake and aftershocks. The events occurred close to the location of water inflow in the mine. A proposed sequence of events is presented. Inflow causes undercutting of pillars and cavern formation, the mine fills with water, hydrostatic pressure is restored, earthquakes occur and, following failure, a stable arch forms.
Int J Min Geol Engng V6. N2, July 1988, P127-146 Construction of a tunnel with a wide span through alternating layers of sandstone and claystone overlain by 2.4m of sandy loam is described. Site investigation included pressuremeter and Lugeon tests in test pits and boreholes, leading to evaluation of discontinuities and joint orientation. The tunnel was constructed using the New Austrian Tunnelling Method, and a 10m reinforced concrete pillar was constructed in an exploratory tunnel in the centre of the 2 tunnel tubes. Stability analysis using the finite element method revealed that the resulting stress distribution showed that the rock mass above the tunnel forms an arch and takes part in stress redistribution around the opening. 893429 Comparison of rock mass disturbance in TBM and drill and blast drivages at the Donkin Mine, Nova Scotia Aston, T R C; Gilby, J L; Yuen, C M K
lnt l Min Geol Engng V6. N2, July 1988, P147-162 Two tunnels were driven through sandstone, one by TBM, the other by drill and blast. A variety of methods were used to assess rock mass disturbance: borehole dilatometer to measure in situ rock modulus, seismic reflection surveys of tunnel sidewalls, laboratory tests on core samples, and in situ gas permeability testing. This showed the borehole dilatometer gave the most realistic evaluation of actual deformation characteristics and TBM excavation caused less damage than drill and blast. The zone of rock mass disturbance compares favourably with numerical and field values from US nuclear waste disposal research.
Tunnels See also: 893207 893426 Influence of engineering geology and rock mechanics in tunnelling Muller, L
lnt Assoc Engng Geol Bull N38, Oct 1988, P5-13 Geological conditions dominate tunnelling, being unaffected by theoretical or economic considerations. They act in a manner predetermined by their nature, yet influenced by the way rock is treated in excavation and support. Factors affecting stand-up times and problems in evaluating these times, and difficulties in interpreting geotechnical data are considered. Contracting and costing complications are discussed. Finally, general advice to the practising engineer on the approach to tunnelling in rock is presented. 893427 Design of tunnel linings in a creeping rock Ladanyi, B; Gill, D E
lnt J Min Geol Engng V6, N2, July 1988, P113-126 The effect of longterm rock deformation on lining pressure is considered using different concepts of rock behaviour. These include the conventional characteristic-line or convergenceconfinement method, modified to allow for rock ageing, and
893430 Soft ground NATM tunnel designs for the Washington, D. C. Metro lrshad, M; Heflin, L H Tunnlg Underground Space Technoi I/3, N4, 1988, P385-392
NATM was used in extension sections of the metro in preference to shield tunnelling or cut and cover. Ground conditions were primarily sands, gravel, and plastic clay with sand lenses. Dewatering was carried out to improve stability, with grouting where necessary. Tunnel design, initial and final linings, excavation sequence, initial support for running tunnels, and shaft and station construction are described. NATM advantages were lower surface settlement, better waterproofing, capital and construction cost savings, and rapid construction. 893431 Slurry and EPB shields Pearse, G
World Tunnlg VI, N4, Dec 1988, P304-315 Problems arising when tunnelling in soft ground are briefly stated, and how shield tunnelling machines overcome them is examined. The various types of shield available, slurry shield, hydroshield, thixshield, earth pressure balance shield, mechanical earth pressure balance shield, and universal shield, are described and particular characteristics noted. Manufacturers are listed.
1989 Pergamon Press pie. Reproduction not permitted RMMS 26-3 .~---P
and (4) uniaxial compression testing. The influence of the threaded rods, drillholes and grout, and width:height ratio of pillars is discussed. Results show that 2 well grouted steel rods significantly increase uniaxial compressive strength, mainly due to the high confining stress provided by the rods as they are tensioned under the transverse strain of the pillar. 893420 Observations, research, and recent results about failure mechanisms around single galleries (In French) Maury, V Proc 6th International Conference on Rock Mechanics, Montreal, 30 Aug-lO Sept 1987 V2, Pl119-1128. Publ Rotterdam: A A Balkema. 1987
893417 Influence of soil surroundings upon the loads of pipes Petrik, P M; Leitner, F Proc ECONMIG 86, Stuttgart, 16-18 September 1986 V2. 7P. Publ Stuttgart: Unieersity of Stuttgart. 1986
Failures of isolated underground structures under simple loadings have been studied. The inability of Mohr-Coulomb type failure criteria to quantitatively predict failure is evident, but they may be able to identify failure modes. Abilities of plastic and elastic theories are examined. Failure initiation is probably inside the wall. Propagation may be by tensile or shear mechanisms, the former probably being more common than was previously realised, The collected work of members of the ISRM Commission on Failure Mechanisms around Underground Openings was the basis of this analysis.
Finite element analysis has been used in a parametric study of the stress and strain fields around flexible and rigid buried pipes. Time dependent behaviour of pipe materials was considered where applicable. Soft and stiff clays, loose and compacted sands, and stabilised backfill soils arc considered. 10 computational algorithms and 5 element types were used. A small selection of the many rcsuhs obtained is illustrated.
89342 I Underground observation of high propagation-rate extension fractures Ortlepp, W D; Moore, M A Proc 6th International Conference on Rock Mechanics, Montreal, 30 Aug-10 Sept 1987 V2. P1173-1180. Publ Rotterdam." A A Balkema, 1987
893418 Space and time variation of microevent parameters occurring in front of an active stope Cichowicz, A: Green, R W E; Van Zyl Brink, A; Grobler, P: Mountfort, P I Proc 2nd International Symposium of Rockbursts and Seism&ity in Mines, Minneapolis, 8-10 June 1988 P213-222. Publ Minneapolis: Unirersity of" Minnesota, 1988
Photographic records of unusual fracture surfaces in the fine grained carbonaceous shale roof of a South African coal mine have been examined. Certain textural features, in particular mirror-zones, suggest very high fracture front propagation rates, up to around 200m/s. Mechanics of the failure have been studied. Gravitational forces alone are seen to be inadequate to cause the failure. Buckling of thinly laminated plates is considered to be the most likely failure mechanism.
Mining operations give rise to a large number of seismic events. A monitoring system was installed 200m ahead of an operational stope. An online numerical program was developed to estimate the seismic moment, seismic energy, corner frequency, static and dynamic stress drop, Q-coda and degree of polarization of microevents. The first 5 parameters describe the seismic source and the last 2 quantify the rock properties. An analysis of the coda signals has shown that the rock mass ~ithin 20m of the stope contains a large proportion of fractured rock. Part of the effort was directed towards investigating variations of the stress drops, Q-coda of the S-wave and the degree of polarization of the P-wave, which could be rockburst precursors. Auth.
893422 Preventative supporting measures to control typical collapse situations in tunnelling (In German) Pacher, F; Vavrovsky, G M Proc 6th International Conference on Rock Mechanics, Montreal, 30 Aug-10 Sept 1987 V2, P1187-1190. Publ Rotterdam. A A Balkema, 1987
Underground excavation failure mechanisms 893419 Reinforcing concrete model pillars with grouted rock bolts Ringwald, J P; Brawner, C O Min Sci Technol V8, NI, Jan 1989, P31-47 Experiments were undertaken to study the improvement in strength and stability of a model pillar due to installation of grouted rock bolts perpendicular to the vertical axis. Theory of failure of a pillar and the effect of the bolt are first outlined. The laboratory test procedure comprised: (1) material testing for sand, reinforcing steel and grout; (2) sample preparation from sand and Portland cement; (3) sample reinforcement;
Failures away from the lace in tunnels are often caused by overloading of the shotcrete lining because of loss of strength and load carrying capacity of the rock mass. It is essential to be able to distinguish between these conditions and less harmful stress redistributions. This can be achieved by careful initial investigation and continuing monitoring of performance.
893423 Performance of deep wellbores in rock with a confining pressure-dependent elastic modulus Santarelli, F J; Brown, E T Proc 6th International Conference on Rock Mechanics,
Atontreal, 30 Aug-10 Sept 1987 V2, P1217-1222. Publ Rotterdam: A A Balkema, 1987 A complete closed form solution is presented for the stresses and displacements induced around an axisymmetric wellbore in rock whose elastic modulus is a function of the minimum principal stress or confining pressure. The theory, which is a generalization of classic linear, constant modulus elastic theory, provides satisfactory explanations of the displacements
¢~ 1989 Pergamon Press plc. Reproduction not permitted
159A and apparent strength enhancement recorded at the walls of model wellbores. An important ramification of the theory is the prediction of a failure pattern in which fractures parallel to the borehole wall may initiate some distance inside the surrounding rock. Auth.
lining-rock interaction methods using models of linear-viscoelastic, linear-elastic linear viscous, and linear elastic non-linear viscous rock behaviour. Calculations of lining pressures show that the former tends to underestimate compared with the latter. Auth.
893424 Mechanical stability of the linkage in deep underground coal gasification (In French) Schmitt, N; Nguyen Minh, D Proe 6tk International Conference on Rock Mechanics,
893428 Design and construction of a shallow tunnel with large span in an urban area Wittke, W
Montreal, 30 Aug-lO Sept 1987 V2, P1223-1226. Publ Rotterdam: A A Balkema, 1987 The linkage tunnel in underground coal gasification must withstand high temperatures (800-1000 deg K) and pressures. The mechanical stability of such a tunnel has been examined using small scale model tests. Mechanical properties of the coal, a non-swelling anthracite, were first measured. Convergence curves were determined under simulated in situ conditions. Results were analysed and a stability criterion proposed. 893425 Seismic activity in a flooded Saskatchewan potash mine Gendzwill, O J; Prugger, A F Proc 2nd International Symposium of Rockbursts and
Seismicity in Mines, Minneapolis, 8-10 June 1988 PI39-148. Publ Minneapolis: Unirersity of Minnesota, 1988 Usually failure in potash mines is due to stress changes associated with subsidence over mined out areas. Failure in a Saskatchewan potash mine which intersected an aquifer, which led to seepage, is described. Initially inflow was controlled by grouting and roof support, but eventually the mine was closed. Soon after, a series of microseismie events occurred, culminating in a magnitude 2.7 earthquake and aftershocks. The events occurred close to the location of water inflow in the mine. A proposed sequence of events is presented. Inflow causes undercutting of pillars and cavern formation, the mine fills with water, hydrostatic pressure is restored, earthquakes occur and, following failure, a stable arch forms.
Int J Min Geol Engng V6. N2, July 1988, P127-146 Construction of a tunnel with a wide span through alternating layers of sandstone and claystone overlain by 2.4m of sandy loam is described. Site investigation included pressuremeter and Lugeon tests in test pits and boreholes, leading to evaluation of discontinuities and joint orientation. The tunnel was constructed using the New Austrian Tunnelling Method, and a 10m reinforced concrete pillar was constructed in an exploratory tunnel in the centre of the 2 tunnel tubes. Stability analysis using the finite element method revealed that the resulting stress distribution showed that the rock mass above the tunnel forms an arch and takes part in stress redistribution around the opening. 893429 Comparison of rock mass disturbance in TBM and drill and blast drivages at the Donkin Mine, Nova Scotia Aston, T R C; Gilby, J L; Yuen, C M K
lnt l Min Geol Engng V6. N2, July 1988, P147-162 Two tunnels were driven through sandstone, one by TBM, the other by drill and blast. A variety of methods were used to assess rock mass disturbance: borehole dilatometer to measure in situ rock modulus, seismic reflection surveys of tunnel sidewalls, laboratory tests on core samples, and in situ gas permeability testing. This showed the borehole dilatometer gave the most realistic evaluation of actual deformation characteristics and TBM excavation caused less damage than drill and blast. The zone of rock mass disturbance compares favourably with numerical and field values from US nuclear waste disposal research.
Tunnels See also: 893207 893426 Influence of engineering geology and rock mechanics in tunnelling Muller, L
lnt Assoc Engng Geol Bull N38, Oct 1988, P5-13 Geological conditions dominate tunnelling, being unaffected by theoretical or economic considerations. They act in a manner predetermined by their nature, yet influenced by the way rock is treated in excavation and support. Factors affecting stand-up times and problems in evaluating these times, and difficulties in interpreting geotechnical data are considered. Contracting and costing complications are discussed. Finally, general advice to the practising engineer on the approach to tunnelling in rock is presented. 893427 Design of tunnel linings in a creeping rock Ladanyi, B; Gill, D E
lnt J Min Geol Engng V6, N2, July 1988, P113-126 The effect of longterm rock deformation on lining pressure is considered using different concepts of rock behaviour. These include the conventional characteristic-line or convergenceconfinement method, modified to allow for rock ageing, and
893430 Soft ground NATM tunnel designs for the Washington, D. C. Metro lrshad, M; Heflin, L H Tunnlg Underground Space Technoi I/3, N4, 1988, P385-392
NATM was used in extension sections of the metro in preference to shield tunnelling or cut and cover. Ground conditions were primarily sands, gravel, and plastic clay with sand lenses. Dewatering was carried out to improve stability, with grouting where necessary. Tunnel design, initial and final linings, excavation sequence, initial support for running tunnels, and shaft and station construction are described. NATM advantages were lower surface settlement, better waterproofing, capital and construction cost savings, and rapid construction. 893431 Slurry and EPB shields Pearse, G
World Tunnlg VI, N4, Dec 1988, P304-315 Problems arising when tunnelling in soft ground are briefly stated, and how shield tunnelling machines overcome them is examined. The various types of shield available, slurry shield, hydroshield, thixshield, earth pressure balance shield, mechanical earth pressure balance shield, and universal shield, are described and particular characteristics noted. Manufacturers are listed.
1989 Pergamon Press pie. Reproduction not permitted RMMS 26-3 .~---P