The signature of shear-induced anisotropy in granular media |
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| Institution: | 1. Irstea, Geomechanics Group, ETNA, Grenoble, France;2. SMS-ID, INSA de Lyon, France;3. Laboratoire Sols Solides Structures Risques, UJF-INPG-CNRS, Grenoble, France;1. Graduate School for International Development and Cooperation, Hiroshima University, 1-5-1, Kagamiyama, Higashi-hiroshima 739-8529, Japan;2. Centre for Geotechnical and Materials Modelling, The University of Newcastle, Callaghan, NSW 2308, Australia;1. Hong Kong University of Science and Technology, Hong Kong, China;2. National Technical University of Athens, Greece;3. University of California at Davis, USA |
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| Abstract: | This paper presents a micro-mechanical study on the characteristics of shear-induced anisotropy in granular media. Based on three-dimensional Discrete Element Method (DEM) simulations, the distinct features associated with the evolution of internal granular structure and different anisotropy sources during drained/undrained shearing of granular samples are carefully examined. The study finds that static liquefaction occurs when the geometrical anisotropy in a sample dominates the mechanical anisotropy in the overall shear strength, and the weak force network features an exceptionally high proportion of sliding contacts and develops certain degree of anisotropy. Phase transformation corresponds to a transitional, unstable state associated with a dramatic change in both coordination number and the proportion of sliding contacts in all contacts. The critical state in a granular material is always associated with a highly anisotropic fabric structure wherein both the critical void ratio and critical fabric anisotropy are uniquely related to the mean effective stress. The relations provide a more comprehensive definition for the critical state in granular media with proper reference to the critical fabric anisotropy. |
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