Physical and MPM modelling of sand column collapse with different moisture and density conditions

Abstract

The sand column collapse test is a simple but useful experiment for investigating the dynamic behaviour of granular flow, which is an important topic in engineering geology and the validation of numerical models. Previous studies have not adequately considered the influence of soil moisture and density conditions. In this study, a series of sand column collapse tests were conducted, considering five water contents ranging from 0 to 10 % and two relative densities of 40 % and 58 %. Particle Image Velocimetry (PIV) was utilised to post-process the experimental results. A hydro-mechanical coupled Material Point Method (MPM), improved by incorporating a non-linear strain hardening/softening law, was employed to back-analyse the physical model tests. The measured and computed results show that as water content increases, the degree of collapse and post-collapse runout distance initially decrease, consistent with changes in Bishop's stress, affected by suction and interparticle water meniscus. As relative density increases, both the degree of collapse and the post-collapse runout distance decrease due to the greater shear strength and Bishop's stress. The MPM simulations closely matched experimental results, confirming the model's accuracy in simulating large deformations in both dry and unsaturated soils.