Study on the macroscopic deformation characteristics and failure mechanisms of rock bridge specimens under compressive shear stress state

Abstract

Abstract Rock bridges play a critical role in the initiation and evolution of tectonic earthquakes and locked-type landslides. However, existing laboratory methods have limitations in reproducing compressive-shear stress conditions and capturing the deformation evolution of rock bridges, restricting a comprehensive understanding of their failure mechanisms. To address these issues, this study proposes a uniaxial compression testing method for rock bridge specimens containing discontinuous cracks. Specimens with different rock bridge angles were designed to induce compressive-shear-dominated stress states within the rock bridge region under uniaxial loading. The deformation and failure processes were investigated by integrating mechanical response analysis, acoustic emission monitoring, and digital image correlation measurements. The results demonstrate that the proposed testing method effectively reproduces the macroscopic deformation characteristics and failure modes of rock bridges under compressive-shear conditions. Specimens with different rock bridge angles exhibited a characteristic valley-shaped evolution of AE activity, while the distributions of average frequency and rise angle parameters indicated that failure was predominantly governed by shear cracking. In addition, DIC measurements revealed the development of a nearly circular vertical displacement field immediately before failure, providing experimental evidence for the formation of circular slip surfaces in homogeneous three-stage locked-type landslides. These findings improve the experimental characterization of rock bridge shear failure and provide new insights into the mechanisms governing circular slip surface formation, offering a useful experimental basis for investigating rock bridge failure and related geological hazards.