The prevention and the reduction of the rockfall are the common measures of the prevention and the reduction of disasters. When the rock-shed resists the impact of the rockfall, the force that acts on the structure consists of the cushion dead load and the impact-induced load, of which the dynamic process of the propagation of the impactinduced load is complex. Therefore, we conducted a numerical study to investigate the impact of the rockfall. Considering the highly discrete characteristic of

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... he sand, we developed a numerical model on the basis of the discrete element method (DEM). The numerical model, which simulation results were validated by the results of real-scale experiments, was used to investigate the dynamic response of the impact force of the rockfall and the transmission of the impact force under the different magnitude of the falling height and the different thickness of the sand cushion. The results of our study indicated that the cushion thickness had little effect on the impact of the rockfall, and the dense sand cushion generated higher impact force than did the loose sand cushion. Although the high thickness enhanced the buffer performance of the sand cushion, the additional force induced by the dead load of sand cushion was significant. Therefore, to determine the appropriate thickness of the sand cushion, we suggested designers consider the buffer performance and the dead load of the sand cushion. The analysis presented in this paper provided a practical estimation of the impact-induced force of the thick sand cushion.