Macro- and micro-mechanical investigations on liquefaction behaviour of granular material under bi-directional simple shear

This paper presents a comprehensive study of initial- and re-liquefaction behaviour of granular material under bi-directional simple shear by conducting experiments and numerical simulations based on the discrete element method (DEM). In the initial liquefaction stage, various linear and non-linear cyclic loading paths are considered, including cases with and without static shear consolidation (SSC). In the re-liquefaction stage, the linear cyclic loading path along one direction is adopted. It is shown that DEM results are in good agreement with experimental data. The presence of SSC increases liquefaction resistance of granular material, and the reason is related to the initial dense state of granular materials. The re-liquefaction stage features a higher liquefaction resistance than the initial liquefaction stage does. Liquefaction resistance of granular material for various bi-directional simple shear cases is demonstrably related to the characteristics of relative density, amount of principal stress rotation (PSR), coordination number, and initial fabric anisotropy of specimens.