Patterns of shear band, precursors to shear failure occurring in strain-softening stage, axial, lateral and volumetric strains as well as Poisson＇s ratio of plane strain rock specimens in compression for different he...Patterns of shear band, precursors to shear failure occurring in strain-softening stage, axial, lateral and volumetric strains as well as Poisson＇s ratio of plane strain rock specimens in compression for different heights were investigated by use of Fast Lagrangian Analysis of Continua（FLAC）. A material imperfection closer to the lower-left corner of the specimen was prescribed. For finer mesh, the imperfection was modeled by four null elements, while it was modeled by a null element for coarser mesh. FISH functions were written to calculate the entire deformational characteristics of the specimen. In elastic stage, the adopted constitutive relation was linear elastic; in strain-softening stage, a composite Mohr-Coulomb criterion with tension cut-off and a post-peak linear constitutive relation were adopted. Height of rock specimen does not influence shear band＇s pattern （including the thickness and inclination angle of shear band）. The slopes of the post-peak stress-axial strain curve, stress-lateral strain curve, lateral strain-axial strain curve, Poisson＇s ratio-axial strain curve and volumetric strain-axial strain curve depend on the height. Hence, the slopes of these curves cannot be considered as material properties. Nonlinear deformation prior to the peak stress is a kind of precursors to shear failure, which is less apparent for shorter specimen. For the same axial strain, lower lateral expansion is reached for shorter specimen, leading to lower Poisson＇s ratio and higher volumetric strain. The maximum volumetric strain of longer specimen is less than that of shorter specimen. The conclusions drawn from numerical results using finer mesh qualitatively agree with those using coarser mesh.展开更多
Scale effect is one of the important aspects in the macro mechanical parame- ters’ research of rock mass, from a new point of view, by means of lab and field rock me- chanics test, establishment of E^Vp relation, cla...Scale effect is one of the important aspects in the macro mechanical parame- ters’ research of rock mass, from a new point of view, by means of lab and field rock me- chanics test, establishment of E^Vp relation, classification of engineering rock mass, nu- merical simulation test and back analysis based on surrounding rock’s displacement monitoring results of Shuibuya Project’s underground power station, rock mass deforma- tion module’s size effect of surrounding rock of Shuibuya Project’s undegroud power sta- tion was studied. It’s shown that rock mass deformation module’s scale effect of sur- rounding rock of Shuibuya Project’s undeground power station is obvious, the rock mass deformation module to tranquilization is 20% of intact rock’s. Finally the relation between rock mass deformation modules and the scale of research was established.展开更多
基金Supported by the National Natural Science Foundation of China(50309004)
文摘Patterns of shear band, precursors to shear failure occurring in strain-softening stage, axial, lateral and volumetric strains as well as Poisson＇s ratio of plane strain rock specimens in compression for different heights were investigated by use of Fast Lagrangian Analysis of Continua（FLAC）. A material imperfection closer to the lower-left corner of the specimen was prescribed. For finer mesh, the imperfection was modeled by four null elements, while it was modeled by a null element for coarser mesh. FISH functions were written to calculate the entire deformational characteristics of the specimen. In elastic stage, the adopted constitutive relation was linear elastic; in strain-softening stage, a composite Mohr-Coulomb criterion with tension cut-off and a post-peak linear constitutive relation were adopted. Height of rock specimen does not influence shear band＇s pattern （including the thickness and inclination angle of shear band）. The slopes of the post-peak stress-axial strain curve, stress-lateral strain curve, lateral strain-axial strain curve, Poisson＇s ratio-axial strain curve and volumetric strain-axial strain curve depend on the height. Hence, the slopes of these curves cannot be considered as material properties. Nonlinear deformation prior to the peak stress is a kind of precursors to shear failure, which is less apparent for shorter specimen. For the same axial strain, lower lateral expansion is reached for shorter specimen, leading to lower Poisson＇s ratio and higher volumetric strain. The maximum volumetric strain of longer specimen is less than that of shorter specimen. The conclusions drawn from numerical results using finer mesh qualitatively agree with those using coarser mesh.
文摘Scale effect is one of the important aspects in the macro mechanical parame- ters’ research of rock mass, from a new point of view, by means of lab and field rock me- chanics test, establishment of E^Vp relation, classification of engineering rock mass, nu- merical simulation test and back analysis based on surrounding rock’s displacement monitoring results of Shuibuya Project’s underground power station, rock mass deforma- tion module’s size effect of surrounding rock of Shuibuya Project’s undegroud power sta- tion was studied. It’s shown that rock mass deformation module’s scale effect of sur- rounding rock of Shuibuya Project’s undeground power station is obvious, the rock mass deformation module to tranquilization is 20% of intact rock’s. Finally the relation between rock mass deformation modules and the scale of research was established.
