Discrete Element Simulation of Soil Liquefaction: Fabric Evolution, Large Deformation, and Multi-Directional Loading

Understanding evolution of microstructure in granular soils can provide significant insights into constitutive modeling of soil liquefaction. By tracing all particle movement, the discrete element modeling (DEM) quantifies the microstructure of a granular assemblage using a variety of fabric indices, such as the numbers of contacts, orientation of contact normal, as well as particles, and voids distribution. The DEM simulations revealed significant change in particle-void fabric to a strongly anisotropic state after initiation of liquefaction. Large flow deformations in the post-liquefaction stage were found to be closely correlated to the evolving particle-void fabric. In addition, fabric evolution in soil packings was also investigated under a variety of multi-directional loading paths. Interestingly, the contact-based fabric ultimately becomes almost identical for all oval and circular loading. The discrete element modeling provides insightful observation that links microscopic fabric evolution to macroscopic cyclic behavior of soils, which is instrumental for developing micromechanically based constitutive models.