A shed cave structure with a sand cushion is often used as a protective structure for rockfall disasters. Because of the randomness and unpredictability of rockfall disasters, the cushions of shed caves often suffer multiple impacts from rockfalls. Aiming at the problem of multiple impacts of rockfall, this paper uses the three-dimensional discrete element method to study the dynamic response of multiple rockfall impacts on sand cushions from different heights. Before conducting large-scale simulation studies, the input parameters in the numerical model are verified with data from laboratory experiments. Analyzing the simulation results shows that when the same point is impacted multiple times, the maximum impact force and the maximum penetration depth will increase with the number of impacts. According to the numerical results, a calculation formula of the maximum impact force that considers the number of impacts is fitted. At the same time, considering the impact response when the rockfall impacts different positions multiple times, the distance range that the subsequent impact is not affected by the previous impact is given. The significance of studying the multiple impacts of rockfalls is shown by a numerical study of rockfalls impacting a sand cushion multiple times from different heights, and it provides a reference for the design of rockfall disaster-protection structures in practical engineering.

Shed structures are an important engineering method for mountain highways to resist rockfall impacts. Research on the rockfall impact response is very important to the design of rockfall disaster protection structures to shed cave structures. To explore the impact difference caused by different rockfall shapes, five mortar ellipsoids were fabricated with different shapes by 3D printing the falling stone mould. Laboratory experiments were carried out to study the impact effect of five different shapes of falling stones on the sand cushion. Different shapes of rockfall correspond to different impact forces. The tip ellipsoid (D1 and D2) is the smallest, the sphere (D3) is the second, and the flat ellipsoid (D4 and D5) is the largest. The fitting analysis of the impact force results of the laboratory experiment showed that the impact of the falling height on the impact force was relatively independent and did not change with the shape of the falling rock. Then, based on the impact force of the sphere falling rock, a calculation formula of the impact force with the introduction of the shape factor was obtained, and it was compared and verified with the test results from other studies. To study the applicability of the formula in the actual engineering scale, a numerical model was established by ANSYS. After verifying the reliability of the numerical model, the impact process of a large energy level was simulated. According to the simulation results, the rationality of the formula proposed in this paper is further verified, which guides the actual rockfall impact prevention and control engineering.