Dynamic Sliding Behavior of Sand-Filled Rock Joints Under Impact Loading: Evolution of Particle-Size Effects

Abstract

Blocky-rock masses are prone to dynamic slip along sand-filled joints under impact disturbance. The constraint normal to the joint and the size of the infill particles jointly influence their stability. To determine how axial load and particle-size affect dynamic slip, this study uses a custom-developed dynamic slip testing system for blocky-rock masses. Impact-disturbance tests are conducted under a constant lateral shear load with different axial load values and quartz-sand particle sizes. The block displacement evolves through three stages: stationary incubation, rapid slip, and deceleration to a stable state. When the axial load increases from 100 N to 400 N, residual slip displacement decreases by 87.52% to 90.12% across the particle size conditions. Residual slip displacement also follows an exponential decay with increasing axial load. Reducing particle size decreases both slip velocity and residual slip displacement, but its influence gradually weakens as the axial load increases. The difference in residual slip displacement between the coarse and fine particle conditions narrows from 0.460 mm to 0.030 mm. Strengthening the normal constraint compacts the granular layer and restricts particle movement, causing the dynamic slippage at sand-containing structural interfaces to gradually shift from being significantly influenced by the particle scale to being primarily controlled by the normal constraint.