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Kinematic element method for 3-D-problems in geomechanics
77A 892211 Initializing the equilibrium stress state for stress analyses in geomechanics Parrish, D K; Labreche, D A Key Questions in Rock Mechanics: Proc 29th US Symposium, Minneapolis, 13-15 June 1988 P303-310. Publ Rotterdam: A
A Balkema, 1988
Drilling 892214 Model trials for test drilling to anticipate rockburst hazard (In German) Tokar, G
Gluckauf-forschungsh V49. N4. Aug 1988, P191-198
Finite element analyses were used to illustrate the significantly different initial conditions that can result from different procedures for initializing the equilibrium stress state for analyses of complex geological domains. The closest approximation to the desired initial equilibrium stress field resulted from using an iterative procedure to initialize the pre-existing stress field. Simple gravity loading, that is,the application of body forces to structurally complex domains with no pre-existing stresses, produced an initial equilibrium stress field that deviated from the in situ stress idealisation selected for an example problem. Auth.
892212 Kinematic element method for 3-D-problems in geomechanics Gussmann, P
Proc ECONMIG 86, Stuttgart, 16-18 Sept 1986 V2, 14P. Publ Stuttgart." University of Stuttgart, 1986 The Kinematic Element Method (KEM) which was previously developed for 2D problems only, has been extended to 3 dimensions. It enables 3D plasticity solutions using the Coulomb criterion to be applied to more general conditions than before. The geometry of the elements is described,and determination of the kinematics and statics of the problem illustrated. An example in the field of passive earth pressure is presented.
Model tests were conducted to investigate the test drilling process. The drilling mass depends on the prevailing stress, and borehole bumps exhibiting differing intensity according to the degree of stress were observed. The sample blocks disintegrated to a fine dust, the cuttings were powdery in consistency, and after borehole bumps the drill becomes jammed or the borehole closes up. Up to a certain limit pressure, cutting mass increases slightly, and over this significantly. Pronounced borehole bumps which go beyond a slight breaking of the sample block only occur in the tests when the initial axial pressure is low. Auth. 892215 River crossings - !. Subsurface soils affect horizontally drilled river-crossing design Hair, J D; Hair, C W
Oil Gas J V86, N38, 19 Sept 1988, P96-100 River crossings are generally accomplished with a small diameter pilot bore which is reamed to size. The pilot is generally drilled with a non-rotating drill string with an angular offset or deflection shoe at the leading edge, and a downholc mud motor. Soil properties influence downhole soil behaviour, with cohesive soils generally behaving with the characteristics of an open hole structure and cohesionless soils behaving in a fluid manner. Combinations of soil types may exist and conditions may change rapidly. Process limitations, construction effects, and drilled path geometry are also examined. 8922 ! 6 River crossings - conclusion. River-activity history evaluation critical in horizontally drilled crossing design Hair, J D; Hair, C W
Design methods
Oil Gas J V86, N39, 26 Sept 1988, P65-68
See." 892385
Rock Breakage and Excavation Rock fracture under dynamic stresses 892213 Modelling gas pressure effects on explosive rock breakage: short communication Haghighi, R; Britton, R R; Skidmore, D
lnt J Min Geol gngng V6, NI. March 1988, P73-79 A finite element model to characterise a blast in a single 102mm diameter hole has been developed. Four cases are considered: (I) homogeneous rock; (2) rock mass weakened by radial cracks; (3) rock mass weakened with cracks and explosive gas pressure in the borehole; and (4) partial pressurisation of cracks as well as borehole. The last case is the most realistic when compared with field data.
River activity mechanisms and their interpretation to predict in situ soil conditions are briefly outlined. Crossing alignment is decided on the basis of this information. Requirements for site investigation, spacing and depth of borings, and sampling are suggested. Pilot hole logging can be used to gather data important when installing the main pipeline. Frictional forces during pullthrough can be estimated and due allowances made.
Blasting 892217 Lower blasthole pressures: a means of reducing costs when blasting rocks of low to moderate strength Hagan, T N; Gibson, I M
lnt J Min Geoi Engng V6, N1, March 1988, PI-13 In blasting, ANFO is mechanically suited to moderate strength rocks, whilst weaker rocks should be blasted using explosives with lower peak pressures. The effects of decking, rock properties, and explosive properties, density and reaction rate on the extent of crushing, which should be avoided, are discussed. It is proposed that crushing and the associated energy loss may be eliminated through improved charge design, and cost effective applications of lower pressure charges are outlined.
© 1989 Pergamon Press plc. Reproduction not permitted
A Balkema, 1988
Drilling 892214 Model trials for test drilling to anticipate rockburst hazard (In German) Tokar, G
Gluckauf-forschungsh V49. N4. Aug 1988, P191-198
Finite element analyses were used to illustrate the significantly different initial conditions that can result from different procedures for initializing the equilibrium stress state for analyses of complex geological domains. The closest approximation to the desired initial equilibrium stress field resulted from using an iterative procedure to initialize the pre-existing stress field. Simple gravity loading, that is,the application of body forces to structurally complex domains with no pre-existing stresses, produced an initial equilibrium stress field that deviated from the in situ stress idealisation selected for an example problem. Auth.
892212 Kinematic element method for 3-D-problems in geomechanics Gussmann, P
Proc ECONMIG 86, Stuttgart, 16-18 Sept 1986 V2, 14P. Publ Stuttgart." University of Stuttgart, 1986 The Kinematic Element Method (KEM) which was previously developed for 2D problems only, has been extended to 3 dimensions. It enables 3D plasticity solutions using the Coulomb criterion to be applied to more general conditions than before. The geometry of the elements is described,and determination of the kinematics and statics of the problem illustrated. An example in the field of passive earth pressure is presented.
Model tests were conducted to investigate the test drilling process. The drilling mass depends on the prevailing stress, and borehole bumps exhibiting differing intensity according to the degree of stress were observed. The sample blocks disintegrated to a fine dust, the cuttings were powdery in consistency, and after borehole bumps the drill becomes jammed or the borehole closes up. Up to a certain limit pressure, cutting mass increases slightly, and over this significantly. Pronounced borehole bumps which go beyond a slight breaking of the sample block only occur in the tests when the initial axial pressure is low. Auth. 892215 River crossings - !. Subsurface soils affect horizontally drilled river-crossing design Hair, J D; Hair, C W
Oil Gas J V86, N38, 19 Sept 1988, P96-100 River crossings are generally accomplished with a small diameter pilot bore which is reamed to size. The pilot is generally drilled with a non-rotating drill string with an angular offset or deflection shoe at the leading edge, and a downholc mud motor. Soil properties influence downhole soil behaviour, with cohesive soils generally behaving with the characteristics of an open hole structure and cohesionless soils behaving in a fluid manner. Combinations of soil types may exist and conditions may change rapidly. Process limitations, construction effects, and drilled path geometry are also examined. 8922 ! 6 River crossings - conclusion. River-activity history evaluation critical in horizontally drilled crossing design Hair, J D; Hair, C W
Design methods
Oil Gas J V86, N39, 26 Sept 1988, P65-68
See." 892385
Rock Breakage and Excavation Rock fracture under dynamic stresses 892213 Modelling gas pressure effects on explosive rock breakage: short communication Haghighi, R; Britton, R R; Skidmore, D
lnt J Min Geol gngng V6, NI. March 1988, P73-79 A finite element model to characterise a blast in a single 102mm diameter hole has been developed. Four cases are considered: (I) homogeneous rock; (2) rock mass weakened by radial cracks; (3) rock mass weakened with cracks and explosive gas pressure in the borehole; and (4) partial pressurisation of cracks as well as borehole. The last case is the most realistic when compared with field data.
River activity mechanisms and their interpretation to predict in situ soil conditions are briefly outlined. Crossing alignment is decided on the basis of this information. Requirements for site investigation, spacing and depth of borings, and sampling are suggested. Pilot hole logging can be used to gather data important when installing the main pipeline. Frictional forces during pullthrough can be estimated and due allowances made.
Blasting 892217 Lower blasthole pressures: a means of reducing costs when blasting rocks of low to moderate strength Hagan, T N; Gibson, I M
lnt J Min Geoi Engng V6, N1, March 1988, PI-13 In blasting, ANFO is mechanically suited to moderate strength rocks, whilst weaker rocks should be blasted using explosives with lower peak pressures. The effects of decking, rock properties, and explosive properties, density and reaction rate on the extent of crushing, which should be avoided, are discussed. It is proposed that crushing and the associated energy loss may be eliminated through improved charge design, and cost effective applications of lower pressure charges are outlined.
© 1989 Pergamon Press plc. Reproduction not permitted