Experimental study on the collapse of partially immersed axisymmetric granular columns

An experimental study on the collapse of partially immersed granular columns is investigated, mainly considering the effects of aspect ratio and water depth on the granular dynamic and final deposit. According to the dimensionless time of collapse, two asymptotic regimes of the partially immersed granular column collapse were found, which are a regime similar to the free fall flow regime and a regime similar to the completely immersed inertial flow regime. Due to the incomplete impregnation of the granular materials and the evolution of the free fluid surface, the fluid resistance generated by the fluid covering the granular materials surface was discovered, which led to the difference between the partially immersed case and the completely dry or immersed case. In addition, we analyze the effect of water depth on the dynamics of granular collapse and deposit properties. Finally, a prediction model for the final runout distance of partially immersed granular collapse in relation to the water depth and aspect ratio was established and validated with the experimental data.