Effects of rock shape on the cushioning mechanics of rock-filled gabions

Abstract

Rock-filled gabions are commonly installed in front of reinforced concrete structures to reduce concentrated impact loads induced by rock fall and boulders entrained in debris flows. The cushioning performance of rock-filled gabions may vary depending on the shape of rock fragments used. In this paper, a parametric study was carried out using the discrete element method to discern the effects of particle shape on the cushioning performance of rock-filled gabion against dynamic boulder impact. Four particle sphericities were adopted to model angular, sub-angular, sub-rounded and rounded particles. DEM simulations reveal that the boulder penetration depth decreases with particle angularity. Thus, a thicker cushioning layer should be used in design if particles are rounded. More importantly, the impact and transmitted forces on a reinforced concrete barrier increased with particle angularity. This is because angular assemblies have more contact points, which enable more stable force chains that can sustain higher loads. The load diffusion angle for rounded particles is up to 20° larger compared to angular particles, suggesting that as particle angularity governs the load spreading ability of a cushioning layer. In general, rocks with rounded morphology should be adopted where possible to reduce transmitted loads and distribute loads more uniformly.