Impact dynamics of granular flow on rigid barriers: insights from numerical investigation using material point method

In order to advance the understanding of the impact dynamics of granular flow in complex geological settings, this paper studied the impact dynamics of granular flow on rigid barriers with a number of Material Point Method（MPM） numerical tests. The impact behavior of granular flow on a rigid barrier was characterized by the initial dynamic impact stage, dynamic surge impact stage, compression impact stage and static stage of granular flow, where the impact force of granular flow was comprised of the dynamic and static forces of granular flow. The impact behavior of granular flow on a rigid barrier was characterized by the states of the fast or slow impact behavior of granular flow. The angle of slope and aspect ratio of granular soil greatly affected the impact behavior of granular flow on a column rigid barrier, where a power model was proposed to quantify the residual(Fnr)-over-maximum(Fnmax) normal impact force ratio of granular flow Fnr / Fnmax incorporating the effects of the angle of slope and aspect ratio of granular soil. With the increase of the column rigid barrier up to the semi-infinite column rigid barrier, the impact dynamics of granular flow gradually increased up to a maximum by progressively transforming the overflow into the dynamic surge impact of the incoming flow on the rigid barrier to capture more granular soil of granular flow against the rigid barrier. Presence of water in granular flow, i.e., a mixture of solid and liquid in granular flow, yielded a dynamic coupling contribution of the solid and liquid, being accompanied by the whole dynamic process of granular flow, on the impact behavior of granular flow on a rigid barrier, where the liquid-phase material of granular flow, i.e., the water, was predominant to contribute on the normal impact force of granular flow in comparison with the solid-phase material of granular flow. In addition, other factors, e.g., the shape of rigid barrier（i.e., the column barrier, arch barrier and circle barrier）, and the gravity（i.e., in the gravitational environment of the Moon, Earth and Mars）, greatly affected the impact behavior of granular flow on a rigid barrier as well.