Analytical Study for Stress Wave Interaction with Rock Joints Having Unequally Close-Open Behavior

Stress wave interaction with rock joints during wave propagation is usually dependent on the dynamic response of the joints. During wave propagation, joints may be closed and open under the effects of the stress wave and the in situ stress. A joint in nature can only resist load during close process. In this paper, the close and open behaviors of rock joints are considered to be different. The joints are assumed to be linearly elastic in close status but turn into free surfaces in open status. Wave propagation equation across joints with unequally close-open behavior is first derived and expressed as a time-differential form based on the displacement discontinuity method. SHPB test recording is then adopted to verify the present approach, which is also compared with the results from existing methods for joints with equally close-open behavior. Next, analysis is conduced for wave propagation across a single joint and a set of parallel joints with unequally close-open behavior, respectively. From the analysis, effects of unequally close-open behavior of a joint on wave propagation and the dynamic response of the joint are studied finally.