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Case studies of hydraulic fracture stress measurement in Australia
ANALYSIS TECHNIQUES:DESIGN METHODS the frequency distribution of discontinuity spacing even in the same rock. -from Authors
Stress analysis 944234 U n d r a i n e d strength interrelationships among CIUC, UU, and UC tests Yit-Yin C h e n & F. H. Kulhawy, Journal of Geotechnical Engineering - ASCE, 119(11), 1993, pp 1732-1750. Consolldated-isotropically undrained, triaxial compression (CIUC), unconsolidated-undrained, triaxial compression (UU), and unconfined compression (UC) test results were used to develop interrelationships for the undrained shear strengths (s.) obtained from these test types. The results show that tile normalized undrained strengths axe dependent on the overconsolidation ratio or undrained strength ratio. Softer clays have lower normalized undrained strength, while harder clays result in higher normalized undrained strength. Suggested correlations for these normalized undrained strengths or undrained strength ratios, as well as the linear regression data and confidence intervals corresponding to one standard deviation, are presented. -from Authors 944235 Numerical analysis of d r a i n e d direct and simple s h e a r tests G. T. Dounias & D. M. Ports, Journal of Geotechnical Engineering- ASCE, 119(12), 1993, pp 1870-1891. Drained direct and simple shear tests are analyzed assuming an isotropic elastoplastic constitutive law and plane strain conditions. Direct shear tests overestimated the initial stiffness and in most cases the peak strength by as much as 7.5%. Stress and strain distribution in the simple shear test become highly nonuniform as peak conditions are approached. The findings agree in general with some reported experimental observations. Analyses where strain softening was modeled did not develop any significant progressive failure, despite of the nonuniform stresses and strains. -from Authors 944236 F o r m a t i o n of MIT-E3 constitutive model for overconsolidated clays A . J . Whittle & M. J. Kavvadas, Journal of Geotechnical Engineering - ASCE, 120(1), 1994, pp 173-198. This paper presents a generalized effective stress model for describing the rate-independent behavior of normally to moderately overconsolidated clays that exhibit normalized behavior. The model formulation comprises three components: 1) an elastoplastic model for normally consolidated clay including anisotropic and strain-softening behavior; 2) equations to describe the small strain nonlinearity and hysteretic response in unloading and reloading; and 3) bounding surface plasticity for irrecoverable, anisotropic, and path-dependent behavior of overconsolidated clays. -from Authors 944237 Model prediction of anisotropic behavior of Boston blue clay A . J . Whittle, D. J. DeGroot, C. C. Ladd & Tian-Ho Seah, Journal of Geotechnical Engineering - ASCE, 120(2), 1994, pp 199-224. This paper investigates predictive capabilities of the effective stress soil model MIT-E3 through detailed comparisons with laboratory test data for Boston blue clay (BBC). The main focus of these evaluations is predictions of anisotropic stress-strain behavior using data from two special laboratory shear devices: the directional shear cell (DSC), and the Multidirectional direct simple shear apparatus (MDSS). MIT-E3 predictions are in excellent agreement with measured variations in peak shear resistance and prepeak stress-strain rresponse. -from Authors 944238 Stresses in rock a n d rock masses F . H . Comet, in: Comprehensive rock engineering. Vol. 3, ed J.A. Hudson, (Pergamon), 1993, pp 297-327. The concept of stress as used in rock mechanics is discussed. This leads to the definition of a local stress tensor and to that of a regional stress field. Various methods for measuring or estimating some, or all, components of the local stress tensor are presented. The methods that are
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most commonly used are only briefly ¢,lUoted. Then some common 'rules of thumb' in rock engineering are examined in light of the data from the develol?ing stress data banks. Finally, the problem of stress variation with time is briefly addressed. -from Author 944239 CSIRO triaxial stress m e a s u r e m e n t cell G. Woromicki, in: Comprehensive rock engineering. Vol. 3, ed J.A. Hudson, (Pergamon), 1993, pp 329-394. This chapter provides an in depth introduction to and a review o f the use of HI stress cells. The first half is concorned with the basic information about the instrument, the preparation and operation of overeating tests and test data reduction; the second half contains a discussion of the application of HI cells under special rock conditions, miscellaneous experimental problems and the use of cells for monitoring of rock stresses. -from Author 944240 Case studies of hydraulic f r a c t u r e stress measurement in Australia J . R . Enever, in: Comprehensive rock engineering. Vol. 3, ed Y.A. Hudson, (Pergamon), 1993, pp 497-532. The CSIRO Division of Geomechanics has been actively engaged in hydraulic fracture stress measurement since the mid 1970s. Since then over 2000 tests have been carried out in a wide variety of situations. The experience is summarised in this chapter and used to illustrate the major practical aspects of relevance in testing. The chapter is organised into the following sections: diagnostics of pressure records; interpretation of pressure records; analysis procedures; laboratory measurement of fracture strength; comparison of hydrofracturing with overcoring; applications; and hydrofracturing in a 3D stress field. -after Author
Design methods 944241 Three-dimensional strain analysis in physical models of geological structures J. Morgan, Tectonophysics, 230(3-4), 1994, pp 181-198. A method is outlined for calculating three-dimensional finite strain in physical models of geological structures conraining passive strain markers. This method makes it possible to determine the three-dimensional strain pattern in models of structures that lack any of the types of symmetry that simplified calculations in previous work. The strain m a ~ e r s i n the new method are in the shape of stubby rectangniar prisms or cubes. These form a three-dimensional grid or array occupying each of the active layers in a model. Each of the grids can be described by positions of three families of 'strain marker surfaces', which are contacts between layers of strain markers. -from Author 944242 Subsurface c h a r a c t e r i z a t i o n with solid models N. L. /ones & S. O. Wright, Journal of Geotechnical Engineering - ASCE, 119(11), 1993, pp 1823-1839. Three-dimensional computer models of construction sites and subsurface stratigraphy are useful for visualization, analysis, and design in geotechnical engineering. A useful technique for creating such models is the geometric techniqne known as 'solid modeling'. Solid modeling was originally developed, in the fields of mechanical and aerospace en~nneermg. In these fields, the shape and complexity of objects is relatively simple and well defined as compared to those of the earth's surface and subsurface. Accordingly, because of the complex nature of the surfaces involved, most available modeling systems are not well suited for modeling earth masses. To overcome this difficulty, a technique employing surfaces in the form of triangulated irregular networks (TINs) and set operations was developed. Complicated excavations can be modeled and cross sections, or 'fence' diagrams, can be constructed quickly and easily, anywhere on the model, to display the
Stress analysis 944234 U n d r a i n e d strength interrelationships among CIUC, UU, and UC tests Yit-Yin C h e n & F. H. Kulhawy, Journal of Geotechnical Engineering - ASCE, 119(11), 1993, pp 1732-1750. Consolldated-isotropically undrained, triaxial compression (CIUC), unconsolidated-undrained, triaxial compression (UU), and unconfined compression (UC) test results were used to develop interrelationships for the undrained shear strengths (s.) obtained from these test types. The results show that tile normalized undrained strengths axe dependent on the overconsolidation ratio or undrained strength ratio. Softer clays have lower normalized undrained strength, while harder clays result in higher normalized undrained strength. Suggested correlations for these normalized undrained strengths or undrained strength ratios, as well as the linear regression data and confidence intervals corresponding to one standard deviation, are presented. -from Authors 944235 Numerical analysis of d r a i n e d direct and simple s h e a r tests G. T. Dounias & D. M. Ports, Journal of Geotechnical Engineering- ASCE, 119(12), 1993, pp 1870-1891. Drained direct and simple shear tests are analyzed assuming an isotropic elastoplastic constitutive law and plane strain conditions. Direct shear tests overestimated the initial stiffness and in most cases the peak strength by as much as 7.5%. Stress and strain distribution in the simple shear test become highly nonuniform as peak conditions are approached. The findings agree in general with some reported experimental observations. Analyses where strain softening was modeled did not develop any significant progressive failure, despite of the nonuniform stresses and strains. -from Authors 944236 F o r m a t i o n of MIT-E3 constitutive model for overconsolidated clays A . J . Whittle & M. J. Kavvadas, Journal of Geotechnical Engineering - ASCE, 120(1), 1994, pp 173-198. This paper presents a generalized effective stress model for describing the rate-independent behavior of normally to moderately overconsolidated clays that exhibit normalized behavior. The model formulation comprises three components: 1) an elastoplastic model for normally consolidated clay including anisotropic and strain-softening behavior; 2) equations to describe the small strain nonlinearity and hysteretic response in unloading and reloading; and 3) bounding surface plasticity for irrecoverable, anisotropic, and path-dependent behavior of overconsolidated clays. -from Authors 944237 Model prediction of anisotropic behavior of Boston blue clay A . J . Whittle, D. J. DeGroot, C. C. Ladd & Tian-Ho Seah, Journal of Geotechnical Engineering - ASCE, 120(2), 1994, pp 199-224. This paper investigates predictive capabilities of the effective stress soil model MIT-E3 through detailed comparisons with laboratory test data for Boston blue clay (BBC). The main focus of these evaluations is predictions of anisotropic stress-strain behavior using data from two special laboratory shear devices: the directional shear cell (DSC), and the Multidirectional direct simple shear apparatus (MDSS). MIT-E3 predictions are in excellent agreement with measured variations in peak shear resistance and prepeak stress-strain rresponse. -from Authors 944238 Stresses in rock a n d rock masses F . H . Comet, in: Comprehensive rock engineering. Vol. 3, ed J.A. Hudson, (Pergamon), 1993, pp 297-327. The concept of stress as used in rock mechanics is discussed. This leads to the definition of a local stress tensor and to that of a regional stress field. Various methods for measuring or estimating some, or all, components of the local stress tensor are presented. The methods that are
201A
most commonly used are only briefly ¢,lUoted. Then some common 'rules of thumb' in rock engineering are examined in light of the data from the develol?ing stress data banks. Finally, the problem of stress variation with time is briefly addressed. -from Author 944239 CSIRO triaxial stress m e a s u r e m e n t cell G. Woromicki, in: Comprehensive rock engineering. Vol. 3, ed J.A. Hudson, (Pergamon), 1993, pp 329-394. This chapter provides an in depth introduction to and a review o f the use of HI stress cells. The first half is concorned with the basic information about the instrument, the preparation and operation of overeating tests and test data reduction; the second half contains a discussion of the application of HI cells under special rock conditions, miscellaneous experimental problems and the use of cells for monitoring of rock stresses. -from Author 944240 Case studies of hydraulic f r a c t u r e stress measurement in Australia J . R . Enever, in: Comprehensive rock engineering. Vol. 3, ed Y.A. Hudson, (Pergamon), 1993, pp 497-532. The CSIRO Division of Geomechanics has been actively engaged in hydraulic fracture stress measurement since the mid 1970s. Since then over 2000 tests have been carried out in a wide variety of situations. The experience is summarised in this chapter and used to illustrate the major practical aspects of relevance in testing. The chapter is organised into the following sections: diagnostics of pressure records; interpretation of pressure records; analysis procedures; laboratory measurement of fracture strength; comparison of hydrofracturing with overcoring; applications; and hydrofracturing in a 3D stress field. -after Author
Design methods 944241 Three-dimensional strain analysis in physical models of geological structures J. Morgan, Tectonophysics, 230(3-4), 1994, pp 181-198. A method is outlined for calculating three-dimensional finite strain in physical models of geological structures conraining passive strain markers. This method makes it possible to determine the three-dimensional strain pattern in models of structures that lack any of the types of symmetry that simplified calculations in previous work. The strain m a ~ e r s i n the new method are in the shape of stubby rectangniar prisms or cubes. These form a three-dimensional grid or array occupying each of the active layers in a model. Each of the grids can be described by positions of three families of 'strain marker surfaces', which are contacts between layers of strain markers. -from Author 944242 Subsurface c h a r a c t e r i z a t i o n with solid models N. L. /ones & S. O. Wright, Journal of Geotechnical Engineering - ASCE, 119(11), 1993, pp 1823-1839. Three-dimensional computer models of construction sites and subsurface stratigraphy are useful for visualization, analysis, and design in geotechnical engineering. A useful technique for creating such models is the geometric techniqne known as 'solid modeling'. Solid modeling was originally developed, in the fields of mechanical and aerospace en~nneermg. In these fields, the shape and complexity of objects is relatively simple and well defined as compared to those of the earth's surface and subsurface. Accordingly, because of the complex nature of the surfaces involved, most available modeling systems are not well suited for modeling earth masses. To overcome this difficulty, a technique employing surfaces in the form of triangulated irregular networks (TINs) and set operations was developed. Complicated excavations can be modeled and cross sections, or 'fence' diagrams, can be constructed quickly and easily, anywhere on the model, to display the