Numerical simulation of rockfalls colliding with a gravel cushion with varying thicknesses and particle sizes

A gravel cushion is an effective method for preventing rockfall disasters, but the thickness and particle size of cushion influence the impact response between rockfall and cushion. Based on previous indoor experiments, a numerical model of a rockfall impacting a cushion was built, and the accuracy of the model were verified by comparing with the coefficient of restitution obtained from experimental results. Then, the impact response characteristics during collision between rockfall and cushion, including the impact force on the cushion surface, the impact force on the cushion bottom, and the penetration depth, were studied. It was found that decreasing the cushion thickness can only reduce the impact force on the cushion bottom, while decreasing the particle size of the cushion can reduce both the impact forces on the cushion surface and bottom. With an increase in the falling height of rockfall, both of the impact forces on the cushion surface and bottom consistently increase, and the increase rate of the impact force on the cushion surface is higher than that of the impact force on the cushion bottom. The penetration depth is significantly affected by the particle size of cushion. With an increase in the falling height of rockfall, the penetration depth increases, but when the particle size of cushion is relatively large, the influence of the falling height of rockfall on the penetration depth decreases to some extent. These numerical results provide a widely applicable theoretical foundation for gravel cushions against rockfall disasters.

Automated summary

The thickness and particle size of a gravel cushion have a significant impact on the response between rockfall and cushion. Decreasing cushion thickness only reduces impact force on the cushion bottom, while decreasing particle size can reduce impact forces on both the cushion surface and bottom. The penetration depth is greatly influenced by the particle size of the cushion. Impacts forces increase with rockfall height, with the increase rate on the cushion surface higher than that on the cushion bottom.