Local deformation around cracks within rock masses critically influences rock mass deformation and instability. However, correlation between internal and surface deformation at cracks remains poorly studied. This study prepared rock-like models to analyze the feasibility of using local strain direction deflection as a precursor to surface cracking, and examined the modulating effect of compressive strength on this precursor phenomenon. It discusses the feasibility of using internal strain direction deflection as a precursor to model instability and the influence of strength on this effect. Before instability, strain values on both sides of the internal fracture increases significantly, accompanied by abrupt changes in the deflection angle. Relative slip progressed through three stages: minor deformation, stable deformation, and rapid deformation. During the stable deformation stage, the deflection angle within the compression quadrant was strongly correlated with the sliding velocity. Higher compressive strength resulted in greater internal deformation before instability, more pronounced growth, lower relative sliding velocity, as well as a larger time and stress range over which surface deformation occurred. Lower compressive strength corresponded to a smaller ratio of the recovery stress to the peak strength.
Lu et al. (Tue,) studied this question.