Shear behavior and damage evolution of the interface between rough rock and cemented tailings backfill

Abstract

The shear behavior of the interface between rock and cemented tailings backfill (CTB) is extremely critical to the backfill design and stability of the backfilled underground mined-out areas. The corresponding shear behavior and surface damage can be significantly affected by the roughness of the rock surfaces. In our study, sandstone with the same rough surface were prepared using rock engraving technology. The direct shear tests on the rough rock-CTB interfaces were carried out under four different normal stresses and six different roughness of the rock surfaces. The interfacial shear strength and corresponding surface damage were analyzed. A new shear strength criterion of the rough rock-CTB interface was then proposed and verified. Our study shows that the compressive deformation of the combined specimen is much larger than that of dilatancy under a higher normal stress. The residual shear strength is less affected by the rock surface roughness under lower normal stress. The corresponding shear strength of the rough rock-CTB interface does not necessarily increase with the rock surface roughness due to the large strength difference between the sandstone and CTB. The interfacial damaged zones, which increase with the normal stress, are roughly concentrated in the larger concave section of the corresponding 2D profiles. The established shear strength criterion of the rock-CTB interface consists of basic mechanical and morphology parameters which can be easily estimated by the general laboratory tests. The findings obtained from this study can be used to quantify the effect of the rough rock-CTB interface on the stability of CTB.