Multiple rockfall impacts on a sand cushion composed of non-spherical particles using three-dimensional DEM

Rockfall disaster is one of the primary geological hazards on Earth, and the rock shed with sand cushion plays a crucial role in rockfall protection. Previous studies mainly focused on the dynamic response of rockfall to sand cushion under single impact. However, in actual rockfall disaster, it is common for the rock shed sand cushion to suffer multiple rockfall impacts. This study utilized a three-dimensional discrete element method to investigate the dynamic response of rockfall to the sand cushion under multiple impacts at different heights. For the first time, non-spherical particles were used to simulate the sand particles composing the sand cushion, and comparative analysis confirmed that non-spherical particles better replicate the characteristics of the sand cushion compared to spherical particles. Subsequently, two scenarios of multiple rockfall impact at the same location and multiple rockfall impact at different locations are investigated, and the impact force and penetration depth are analyzed. The results show that when the rockfalls impact multiple times at the same position, the maximum impact force and the maximum penetration depth increase with the number of impacts. When the rockfalls impact multiple times simultaneously at different positions, they have no mutual influence when the distance between the two rockfall impacts is greater than 6R. This study demonstrates the significance of studying multiple rockfall impacts, and provides valuable insights for the rational design of rock sheds for rockfall protection and performance evaluations in the face of multiple rockfall disasters.