Soil cushion layers are commonly paved in front of protection structures to avoid the direct impact of rockfall and debris flow. This study is devoted to investigating the influence of particles size on the buffering efficiency of a soil cushion layer by experimental and numerical tests. A series of experimental tests are performed by releasing a spherical granite rock block from different heights to impact onto a soil cushion layer consisting of uniformly graded particles. The influence of particle grading on the buffering efficiency is then analyzed in a set of parametric studies. The impact force of rock block and the interacting force at the interface between the soil layer and the protection structure are monitored and evaluated. The discrete element method is utilized to explore the cratering process of rock block, together with the force chains and energy evolutions in the soil cushion layer. The results indicate that soil particles size can influence significantly on the impact force, especially for high-velocity impacts. This effect can be explained by the number and the stability of force chains formed in the granular packing. These findings can provide some insights to designing effective soil cushion layers for protection structures.

通常将土壤垫层铺在防护结构的前面，以避免落石和泥石流的直接影响。这项研究致力于通过实验和数值试验研究粒径对土壤垫层缓冲效率的影响。通过从不同高度释放球形花岗岩岩石块以撞击到由均等梯度颗粒组成的土壤垫层上，进行了一系列实验测试。然后在一组参数研究中分析了颗粒分级对缓冲效率的影响。监测和评估了岩石块的冲击力以及在土层与保护结构之间的界面处的相互作用力。利用离散元法探讨了岩石块的缩孔过程，以及土壤垫层中的力链和能量演化。结果表明，土壤颗粒大小可以显着影响冲击力，特别是对于高速冲击。可以通过在粒状填料中形成的力链的数量和稳定性来解释这种效果。这些发现可以为设计用于防护结构的有效土壤垫层提供一些见识。