Shear property and failure mechanism of bonded rock-cement interface: Experimental and numerical approaches

The study of the shear behavior of bonded rock-cement interface is important for understanding the strength and stability of grouted rock masses. This research aims to reveal the failure mechanism behind the shear property of bonded rock-cement interfaces. For the study, sandstone and granite joint blocks with specific morphology were fabricated by using a three-dimensional (3D) engraving technique. Bonded rock-cement joints with asperity inclination angles of 15°, 30°, and 45° were prepared. Shear tests were performed on these bonded rock-cement joints to investigate the shear response and failure modes considering the effect of applied normal stress and interface morphology. Meanwhile, the two-dimensional particle flow code (PFC2D) was utilized to model the entire shear process of bonded rock-cement interfaces. The macroscopic shear behavior and mesoscopic failure mechanism were comprehensively investigated by the laboratory test and numerical simulation. The results showed that the shear stress-displacement curves of bonded rock-cement joints exhibit two distinct peaks, and the shear stress evolution can be categorized into four stages including elastic growth, rapid stress drop, secondary stress growth, and progressive softening. Significantly, the number of acoustic emission events also exhibits two distinct peaks related to the double peak of the shear stress curves. The failure of bonded rock-cement interfaces is mainly induced by shear fractures, while the failure of rock and cement blocks is primarily caused by tensile fractures. The number of shear cracks in the bonded rock-cement interfaces reaches the peak when the shear stress reaches the primary peak; whereas as the shear stress continuously approaches the residual stage, the fracture of the bonded rock-cement joints is primarily characterized by tensile cracks in the blocks.