Macro-micro investigation of granular materials in torsional shear test
来源期刊：中南大学学报(英文版)2014年第7期
论文作者：LI Bo(李博) GUO Lin(郭林) ZHANG Feng-shou(张丰收)
文章页码：2950 - 2961
Key words：hollow cylinder apparatus; numerical modeling; principal stress rotation; strain localization
Abstract: A three-dimensional numerical torsion shear test is presented on hollow cylinder specimen which is performed on a spherical assemblage with fixed principal stress axes using the discrete element code PFC3D. Stack wall technique boundary conditions are employed and optimized to reasonably capture the microstructure evolution. Parametric studies are conducted in terms of the ratio κ, normal and shear stiffness of particles, wall stiffness and friction coefficients. Afterwards, in comparison with physical test, numerical results for a fixed principal stress angle (α=45°) are presented. The results show that the numerical test could capture the macro-micro mechanical behavior of the spherical particle assembly. The evolution of the coordination number demonstrates that particles in shear banding undergo remarkable decrease. The effects of localization on specimens illustrate that global stress and strain recorded from a hollow cylinder apparatus could not represent the localized response. The shearing band initiation and evolution from porosity and shear rate are visualized by contour lines in different shear strains.
LI Bo(李博)1, 2, GUO Lin(郭林)1, ZHANG Feng-shou(张丰收)3
(1. Department of Civil Engineering, Wenzhou University, Wenzhou 325000, China;
2. Guangxi Key Laboratory of Geomechanics and Geotechnical Engineering,
Guilin University of Technology, Guilin 541000, China;
3. Itasca, Houston, Inc., Texas 77001, USA)
Abstract:A three-dimensional numerical torsion shear test is presented on hollow cylinder specimen which is performed on a spherical assemblage with fixed principal stress axes using the discrete element code PFC3D. Stack wall technique boundary conditions are employed and optimized to reasonably capture the microstructure evolution. Parametric studies are conducted in terms of the ratio κ, normal and shear stiffness of particles, wall stiffness and friction coefficients. Afterwards, in comparison with physical test, numerical results for a fixed principal stress angle (α=45°) are presented. The results show that the numerical test could capture the macro-micro mechanical behavior of the spherical particle assembly. The evolution of the coordination number demonstrates that particles in shear banding undergo remarkable decrease. The effects of localization on specimens illustrate that global stress and strain recorded from a hollow cylinder apparatus could not represent the localized response. The shearing band initiation and evolution from porosity and shear rate are visualized by contour lines in different shear strains.
Key words:hollow cylinder apparatus; numerical modeling; principal stress rotation; strain localization
