The microscopic origin of K0 on granular soils: the role of particle shape

Abstract

The at-rest coefficient of lateral pressure, $$K_0$$ , is a critical macroscopic parameter for evaluating stress transmission in granular media for engineering practice. This paper revisits the microscopic origin of $$K_0$$ and its corresponding underlying physics based on micromechanics-based theories and numerical simulations, with a focus placed on the effect of particle shape. Two typical kinds of distortion (elongation and blockiness) in particle shape are considered, modeled by ellipsoids and superballs in the discrete element method. One-dimensional compression tests are performed on numerical specimens with dense and loose initial states for different particle shapes. An analytical relationship between $$K_0$$ and anisotropy of fabric measures (i.e., contact normal, contact force, and shape-related anisotropy) is established within the stress-force-fabric framework. It is found that the analytical $$K_0$$ is consistent with the measured one directly from the simulation regardless of particle shape, verifying a well-established relationship between $$K_0$$ and fabric. It is further found that contact force partition of $$K_0$$ plays the most prominent role in $$K_0$$ compared to contact normal and shape-related partitions. Results also reveal the different influence of shape distortion on $$K_0$$ and the corresponding mechanical properties related to $$K_0$$ , such as void ratio, mobilized friction angle, and coordination number. More specifically, $$K_0$$ has a ‘W’-shape relationship with elongation for dense ellipsoids and an ‘M’-shape relationship with blockiness for superballs.