Roughness Characterization and Shearing Dislocation Failure for Rock-Backfill Interface

Shearing dislocation is a common failure type for rock-backfill interface due to the backfill sedimentation and rock strata movement in backfill mining goaf. This paper designs a test method for rock-backfill shearing dislocation. By digital image technology and three-dimensional (3D) laser morphology scanning technique, a set of 3D models with rough joint surfaces was established. Further, the mechanical behavior of rock-backfill shearing dislocation was investigated based on the direct shear test. The effects of interface roughness on the shear-displacement curve and failure characteristics of rock-backfill specimens were considered. The 3D fractal dimension, profile line JRC (Joint Roughness Coefficient), profile line two-dimensional fractal dimension and the surface curvature of the fractures were obtained. The correlation characterization of surface roughness was then analyzed, and the shear strength can be measured and calculated through JRC. Results show that: there are 3 failure threshold value points in shearing dislocation of rock-backfill, including 30% to 50% displacement before the peak, 70% to 90% displacement before the peak and 100% displacement before the peak to post-peak, which can be a sign for the shearing dislocation failure of rock-backfill. The surface JRC can be used to judge the shearing dislocation failure of rock-backfill including post-peak sliding, uniform variations and gradient change, corresponding to the dislocation failure of rock-backfill on the field site. The research reveals the damage mechanism for rock-backfill complex based on free joint surface, fills the gap of existing shearing theoretical system for isomerism complex and provides theoretical basis for prevention and control of the possible disasters in backfill mining.