Experimental study on multiple impact resistance of geogrid reinforced cushion

Rock-sheds are often used at mountain roads and tunnel entrances for preventing rockfall disasters. Placing geogrids in sand cushion can improve the resistance to rockfall impacts. However, the mechanism of geogrid reinforced sand cushion under multi-impacts remains unclear. This study conducted four model tests to investigate the mechanical response of geogrid-sand cushions with different reinforcement positions under multiple impacts. The results showed that geogrids effectively reduced the impact penetration depth and improved its buffering capacity. When the geogrid was placed at 2/3 the height of the cushion, with increase in the number of impacts, the growth rate of the maximum impact force and peak earth pressure, and the reduction rate of the penetration depth and impact stress factor were the smallest. Moreover, the vibration of the shed roof slab was mitigated. This is because this working condition effectively converted the impact stress into horizontal tensile stress of the geogrid, which is beneficial for evening the distribution of the stress on the shed roof slab. Thus, this study provides a reference for the optimization and design of rock-sheds.