The closure behaviour of rock joints under impact loading

Abstract

The dynamic properties of jointed rock and closure deformation behavior of rock joints under impact loading are of significant importance for a correct understanding of stress wave propagation or dynamic failure in the rock masses, so a serial of impact tests of the intact and joined samples was carried out based on a hammer-driven SHPB device. The cement mortar was used to make regular joint surface asperity for studying the effect of joint surface morphology on its deformation features and a dynamic B-B model was applied to describe closure curve characteristics. The test results demonstrate that the stress-strain curve of jointed rock is obviously influenced by joint roughness and the closure characteristic was affected by joint surface morphology. Specifically, the stress-strain curve of jointed rock exhibited some differences with the intact sample because of the existence of discontinuity and its roughness. the peak stress and elastic modulus of jointed rock were obviously low when compared to the intact samples. Rock joint under impact load exhibited hyperbolic deformation characteristics, and this behavior is not affected by joint surface morphologies. The dynamic initial stiffness increases and maximum allowance closure decrease with the increase of contact area ratio (CAR) and asperity inclination angle.