Numerical study of the collapse of columns of sand immersed in water using two-phase flow modelling

Abstract

In this paper we present a numerical study of the collapse of a column of sand immersed in water. It consists of two-dimensional simulations and is based on a recently developed two-phase thermomechanical theory for granular suspensions. For the shear viscosity of the granular phase, we have tested various parameterizations and selected the one that gave better comparisons with experiments. Our study focuses on the influence of the initial volume fraction and the aspect ratio of the column. The shape of the final deposit, the final-to-initial height ratio, as well as the runout distance and amount of suspended sand are found to be dependent on both parameters. In densely-packed columns, the collapse always starts with the detachment and falling of the top corner. The final deposit is trapezoidal for small and intermediate aspect ratios and triangular for high ones. On the contrary, in loosely-packed columns, the entire lateral side falls while the rest of the column descends and compacts due to its own weight. For loose packings, the final deposit is always trapezoidal for the aspect ratios considered herein, while the final-to-initial height ratio is also considerably lower than for dense packings. Also, the amount of suspended sand is significantly higher for loose packings and it also increases with the aspect ratio. Our numerical predictions are in good agreement with earlier published data on the collapse of sand columns immersed in water.