DEM exploration of confining stress effect in cyclic liquefaction of granular soils

Abstract

Confining stress is a major consideration in the assessment of liquefaction resistance of granular soils. In this study, the influence of confining stress to cyclic liquefaction from micromechanical perspectives are explored using DEM simulations. Eight samples with different confining stresses and void ratios are prepared and subjected to undrained cyclic loading tests to reach initial liquefaction. It is observed that the influence of confining stress to coordination number of the sample before shearing is limited. However, confining stress has a significant influence to probability distribution of normal contact forces. Sample with higher confining stress has higher fraction of medium normal forces. During liquefaction process, evolution of coordination number versus effective vertical stress for all samples converge to a unique curve, which may depict the minimum value of coordination number for the load-bearing structure to sustain the effective stress. Different anisotropic sources undertake different roles in shear resistance. The contribution of tangential contact force anisotropy to shear resistance is gradually replaced by contact normal anisotropy.