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3D hierarchical multiscale modeling (HMM) of strain localization in granular media

We investigate the strain localization in granular media based on 3D hierarchical multiscale model (HMM). This HMM approach uses the finite element method (FEM) to solve the boundary value problem of granular media and derives the local material point responses from embedded discrete element (DEM) simulations to bypass the constitutive assumption required by conventional FEM calculation. Rigorous coupling between FEM and DEM in the HMM enables effective bridging between the micromechanical characterization and the continuum modeling of granular media. The HMM approach is employed to study the initiation and formation of strain localization in granular media under true triaxial loading with different constant intermediate principal stress ratio b. When the axial strain (either compression or extension) is uniformly applied to a sample under smooth loading platen, a constant b condition is maintained by adaptively adjusting the confining pressure applied in the four lateral directions. Our HMM simulations indicate strain localization is more likely to occur at larger Lode angle (i.e. b is large), which is consistent with laboratory observations.

Author(s):

Ning Guo    
Hong Kong University of Science and Technology
Hong Kong

Jidong Zhao    
Hong Kong University of Science and Technology
Hong Kong