Abstract: The impact of rockfall on the shed cave structure is complicated and lacks a unified expression of rockfall impact force. First of all, the falling rock is simplified into a rigid sphere, the theoretical expression of the rockfall impact force is derived using half-sine algorithm based on the Hertz contact theory. Considering the inelastic characteristics of rockfall impact on shed cave, the method of function fitting is used to calculate the impact force of rockfall under normal impact according to the characteristics of the rockfall acceleration curve during the collision between the rock and the material, and then a numerical calculation model of the rockfall impact on shed cave is established to study the dynamic characteristics of the rockfall impact on shed cave at different impact speeds based on ANSYS/LS-DYNA software. Finally, compared with the existing common methods, some conclusions are drawn. The impact force of rockfall obtained by Hertz half sine method is much larger than that obtained by function fitting method and numerical method, and the time-history relationship of rockfall impact force obtained by function fitting method in this paper is close to that obtained by numerical method. It indicats that function fitting method can better reflect the dynamic relationship of the collision between the falling rock and the shed cave. Compared with other calculation methods, it can be obtained that the Hertz algorithm is suitable for analyzing the elastic collision problem without energy loss, and the Logistic algorithm is suitable for the situation of large plastic deformation of the material. There are differences between the elastoplastic contact theory results and the dynamic finite element results, and the maximum impact force and the impact time of the rockfall obtained by the calculation method derived from the function fitting are closer to the dynamic finite element method, and it can better reflect the dynamic response characteristics of the rockfall impact on the shed. The calculation method of rockfall impact force deduced in this paper can provide theoretical reference for the design of protection measures in practical engineering.

Key words: rockfall, contact theory, impact force, impact time, ANSYS/LS-DYNA