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Triaxial testing of naturally cemented carbonate soil
148A
ANALYSIS TECHNIQUES:STRESS
program to monitor possible block movements along the bedding planes is ongoing. The offset shotholes, which are localized on aportion of the wall that forms a thin ridge of rock between the roadcut and a steep draw immediately to the east, are believed to be due to block movements created by blasting operations conducted during construction of the roadcut. -Authors
Stress analysis 943213 Interpretation of hydraulic fracturing breakdown pressure F. Guo, N. R. Morgenstem & J. D. Scott, International Journal o f Rock Mechanics & Mining Sciences, 30(6), 1993, pp 617-626. Breakdown pressure is an important parameter obtained during hydraulic fracturing stress measurements. It is thought that the maximum horizontal stress can be calculated from the breakdown pressure, the minimum principal stress and the properties of the rocks. On the other hand, breakdown is a complex process. The breakdown pressure is rate-dependent, size-dependent, fracture fluid-dependent and o3-dcpendent. As a result, breakdown models prevail. This paper evaluates the various models experimentally and theoretically. The analysis shows that the classical breakdown model, the poroelastic model, the shear failure model and the point stress model cannot explain the observed abnormally high breakdown pressure. The fracture mechanics model is promising. -from Authors 943214 Interpretation of hydraulic fracturing pressure: a comparison of eight methods used to identify shut-in pressure F. Guo, N. R. Morgenstem & J. D. Scott, International Journal of Rock Mechanics & Mining Sciences, 30(6), 1993, pp 627-631. The minimum principal stress is an important factor in the design of underground openings and massive hydraulic fracturing. Hydraulic fracturing is one of the most promising methods for determining the minimum principal stress, especially at great depth. In hydraulic fracturing stress measurements, the mintmum principal stress is assumed to be equal to the shut-in pressure. Considerable shut-in pressure responses were obtained in a laboratory single-well hydraulic fracturing program. All the curves yielded indistinct shut-in pressure because high leak-off was incorporated in the tests. Therefore, the data provide an opportunity to evaluate the anal__ysis techniques to deal with indistinct shut-in pressure. This paper compares the shut-in pressure evaluated by eight different methods with the mmmaum principal stress applied to a specimen. -from Authors 943215 Constitutive behavior and numerical modeling A. Cividini, in: Comprehensive rock engineering. Vol. 1, ed J.A. Hudson, (Pergamon), 1993, pp 395-426. Here the finite element method is considered, in particular, as a practical engineering tool for the solution of stress analysis problems. The discussion is limited to quasi-static conditions and to one-phase (solid) materials.Firstly the equations governing the stress analysis problem for the elastic continuum are recalled. Then, various types of linear and nonlinear, time independent and time dependent constitutive laws are illustrated, with particular reference to those proposed for modeling the mechanical behavior of rocks and softs. The bases of some approaches for numerical stress analysis are subsequently recalled and, finally, the finite element formulations for linear, elasto-plastic and vtsco-plastic stress analyses are discussed in some detail. -from Author 943216 An overview of the b o u n d a r y element methods J . O . Watson, in: Comprehensive rock engineering. Vol. 1, ed J.A. Hudson, (Pergamon), 1993, pp 469-490. Boundary element methods (BEMs) are computational techniques of prediction of stress, groundwater flow and temperature distribution in certain rock masses. This chapter considers only stress prediction, as groundwater and temperature problems are the same in principle and implementation. BEMs are applied to continuous and
discontinuous rock masses (defined by degree of jointing and size of structure under observation). Direct, indirect and displacement discontinuity methods are presented, and finally the coupling of BEMs and finite element methods is detailed. -R.Gower 943217 Cohesion intercept in effective stress-stability analysis G. Mesri & M. E. M. Abdel-Ghaffar, Journal of Geotechnical Engineering - ASCE, 119(8), 1993, pp 1229 - 1249.
The cohesion intercept in the Coulomb shear-strength e.quation has a significant influence on the location of the shp surface and the factor of safety. The cohesion intercept results from a linear approximation of a segment of a nonlinear shear strength against effective normal stress relationship. Peak strength controls local development of slip surface, but it may not be available during global failure. The critical slip surface for an initial slide is determined using the peak shear strength. However, a mobilized strength equal to or less than the peak strength is used to define the factor of safety. Effective stress-stabftity analysis of slope failures has resulted in a reduction factor to the peak strength in order to obtain the mobilized strength for first time slides. -from Authors 943218 The coefficient of earth pressure at rest G. Mesri & T. M. Hayat, Canadian Geotechnical Journal, 30(4), 1993, pp 647-666. Laboratory experiments on undisturbed specimens of a large number of soft clay deposits, as well as previous measurements on clays and granular soils, were used to examine and explain the magnitude and behavior of the coefficient of earth pressure at rest, K . Empirical equations provide reasonable estimates of°K for clays and granular softs after secondary-compressi~)n aging, after preconsolidation by unloading, and for soft clay deposits that display a preconsolidation pressure o" greater than in situ effective vertical stress ¢Y'v • Pr°p°sedPcmp irical equations and methods s u c c e s s f ~ y predict K preshearcd clays. -from Authors 943219 Development of the ultrasonic measurement technique and its a p p l i c a t i o n in the observation of rock mass stability Yonglian Sun, Shftiang Lu & Chuliang Zhou, Geotechnical & Geological Engineering, 11(4), 1993, pp 273-284. A method of measuring ultrasonic wave properties in rocks during the complete stress-strain process is described. A preliminary study was conducted on the application of the ultrasonic measurement technique at a belt conveyor roadway of the north wing in Baodian coal mine, Shandong province. Based on the interrelations between the complete stress-strain properties of specimens and their wave properties, the structural properties of surrounding rocks, the range of yield zones, and the change of stresses within the rocks surrounding a roadway which was subjected to mining influence of upper 1ongwall face were analysed. -from Authors 943220 Triaxial testing of naturally cemented carbonate soil D. W. Airey, Journal o f Geotechnical Engineering ASCE, 119(9), 1993, pp 1379-1398. Cemented carbonate (calcarenite) softs obtained from the North West Shelf of Australia were subjected to conventional and stress-path triaxial tests. Natural calcarenlte specimens were found to have wide variations of dry denslty and degree of cementation. These variations complicate interpretation of the test data, and need to be tal~en into account. To achieve this, it is suggested that tensile tests be performed on off-cuts to estimate the degree of cementatxon. The responses of the natural calearenite sampies were found to be similar to other cemented and structured softs. The cementation was found to increase the shear modulus and size of the yield locus, but to have little effect on the volumetric response. -from Author
ANALYSIS TECHNIQUES:STRESS
program to monitor possible block movements along the bedding planes is ongoing. The offset shotholes, which are localized on aportion of the wall that forms a thin ridge of rock between the roadcut and a steep draw immediately to the east, are believed to be due to block movements created by blasting operations conducted during construction of the roadcut. -Authors
Stress analysis 943213 Interpretation of hydraulic fracturing breakdown pressure F. Guo, N. R. Morgenstem & J. D. Scott, International Journal o f Rock Mechanics & Mining Sciences, 30(6), 1993, pp 617-626. Breakdown pressure is an important parameter obtained during hydraulic fracturing stress measurements. It is thought that the maximum horizontal stress can be calculated from the breakdown pressure, the minimum principal stress and the properties of the rocks. On the other hand, breakdown is a complex process. The breakdown pressure is rate-dependent, size-dependent, fracture fluid-dependent and o3-dcpendent. As a result, breakdown models prevail. This paper evaluates the various models experimentally and theoretically. The analysis shows that the classical breakdown model, the poroelastic model, the shear failure model and the point stress model cannot explain the observed abnormally high breakdown pressure. The fracture mechanics model is promising. -from Authors 943214 Interpretation of hydraulic fracturing pressure: a comparison of eight methods used to identify shut-in pressure F. Guo, N. R. Morgenstem & J. D. Scott, International Journal of Rock Mechanics & Mining Sciences, 30(6), 1993, pp 627-631. The minimum principal stress is an important factor in the design of underground openings and massive hydraulic fracturing. Hydraulic fracturing is one of the most promising methods for determining the minimum principal stress, especially at great depth. In hydraulic fracturing stress measurements, the mintmum principal stress is assumed to be equal to the shut-in pressure. Considerable shut-in pressure responses were obtained in a laboratory single-well hydraulic fracturing program. All the curves yielded indistinct shut-in pressure because high leak-off was incorporated in the tests. Therefore, the data provide an opportunity to evaluate the anal__ysis techniques to deal with indistinct shut-in pressure. This paper compares the shut-in pressure evaluated by eight different methods with the mmmaum principal stress applied to a specimen. -from Authors 943215 Constitutive behavior and numerical modeling A. Cividini, in: Comprehensive rock engineering. Vol. 1, ed J.A. Hudson, (Pergamon), 1993, pp 395-426. Here the finite element method is considered, in particular, as a practical engineering tool for the solution of stress analysis problems. The discussion is limited to quasi-static conditions and to one-phase (solid) materials.Firstly the equations governing the stress analysis problem for the elastic continuum are recalled. Then, various types of linear and nonlinear, time independent and time dependent constitutive laws are illustrated, with particular reference to those proposed for modeling the mechanical behavior of rocks and softs. The bases of some approaches for numerical stress analysis are subsequently recalled and, finally, the finite element formulations for linear, elasto-plastic and vtsco-plastic stress analyses are discussed in some detail. -from Author 943216 An overview of the b o u n d a r y element methods J . O . Watson, in: Comprehensive rock engineering. Vol. 1, ed J.A. Hudson, (Pergamon), 1993, pp 469-490. Boundary element methods (BEMs) are computational techniques of prediction of stress, groundwater flow and temperature distribution in certain rock masses. This chapter considers only stress prediction, as groundwater and temperature problems are the same in principle and implementation. BEMs are applied to continuous and
discontinuous rock masses (defined by degree of jointing and size of structure under observation). Direct, indirect and displacement discontinuity methods are presented, and finally the coupling of BEMs and finite element methods is detailed. -R.Gower 943217 Cohesion intercept in effective stress-stability analysis G. Mesri & M. E. M. Abdel-Ghaffar, Journal of Geotechnical Engineering - ASCE, 119(8), 1993, pp 1229 - 1249.
The cohesion intercept in the Coulomb shear-strength e.quation has a significant influence on the location of the shp surface and the factor of safety. The cohesion intercept results from a linear approximation of a segment of a nonlinear shear strength against effective normal stress relationship. Peak strength controls local development of slip surface, but it may not be available during global failure. The critical slip surface for an initial slide is determined using the peak shear strength. However, a mobilized strength equal to or less than the peak strength is used to define the factor of safety. Effective stress-stabftity analysis of slope failures has resulted in a reduction factor to the peak strength in order to obtain the mobilized strength for first time slides. -from Authors 943218 The coefficient of earth pressure at rest G. Mesri & T. M. Hayat, Canadian Geotechnical Journal, 30(4), 1993, pp 647-666. Laboratory experiments on undisturbed specimens of a large number of soft clay deposits, as well as previous measurements on clays and granular soils, were used to examine and explain the magnitude and behavior of the coefficient of earth pressure at rest, K . Empirical equations provide reasonable estimates of°K for clays and granular softs after secondary-compressi~)n aging, after preconsolidation by unloading, and for soft clay deposits that display a preconsolidation pressure o" greater than in situ effective vertical stress ¢Y'v • Pr°p°sedPcmp irical equations and methods s u c c e s s f ~ y predict K preshearcd clays. -from Authors 943219 Development of the ultrasonic measurement technique and its a p p l i c a t i o n in the observation of rock mass stability Yonglian Sun, Shftiang Lu & Chuliang Zhou, Geotechnical & Geological Engineering, 11(4), 1993, pp 273-284. A method of measuring ultrasonic wave properties in rocks during the complete stress-strain process is described. A preliminary study was conducted on the application of the ultrasonic measurement technique at a belt conveyor roadway of the north wing in Baodian coal mine, Shandong province. Based on the interrelations between the complete stress-strain properties of specimens and their wave properties, the structural properties of surrounding rocks, the range of yield zones, and the change of stresses within the rocks surrounding a roadway which was subjected to mining influence of upper 1ongwall face were analysed. -from Authors 943220 Triaxial testing of naturally cemented carbonate soil D. W. Airey, Journal o f Geotechnical Engineering ASCE, 119(9), 1993, pp 1379-1398. Cemented carbonate (calcarenite) softs obtained from the North West Shelf of Australia were subjected to conventional and stress-path triaxial tests. Natural calcarenlte specimens were found to have wide variations of dry denslty and degree of cementation. These variations complicate interpretation of the test data, and need to be tal~en into account. To achieve this, it is suggested that tensile tests be performed on off-cuts to estimate the degree of cementatxon. The responses of the natural calearenite sampies were found to be similar to other cemented and structured softs. The cementation was found to increase the shear modulus and size of the yield locus, but to have little effect on the volumetric response. -from Author