Influence of particle size on the buffering efficiency of soil cushion layer against rockfall impact

Abstract

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.