Evaluating shear strength and acoustic emission in rock-like materials with non-persistent joint geometries under freeze-thaw conditions.

This study examines the effects of freeze-thaw cycles and the geometric configuration of non-persistent joints on the shear behavior of rock masses. Various artificial rock samples with non-persistent joints underwent direct shear testing to investigate how freeze-thaw cycles (F-T), the rock bridge angle (β), the number of joints (N), and normal stress (σ) influence shear strength and fracture development. Taguchi's method was employed for experimental design, and the impact of the parameters was evaluated using analysis of variance (ANOVA). Additionally, acoustic emission (AE) detection was utilized to reveal the fracturing characteristics of rock bridges during the tests. The results indicate that normal stress has the most significant effect on shear strength, while the number of joints has the least impact. The angle of the rock bridge is the second most crucial factor influencing shear strength; specifically, low angles lead to tensile failure, while higher angles result in a transition to shear failure. AE data shows that tensile failure occurs at high average frequencies (AF) and low rise angle (RA) values, whereas shear failure exhibits the opposite characteristics. F-T cycles rank third in significance. The results indicate that frost heave primarily affects the specimens in the initial stages of the F-T cycles. Furthermore, the direct shear test results for specimens subjected to F-T cycles are categorized into three stages based on acoustic emission (AE) data: a quiet stage, an AE development stage, and a drop AE stage. Notably, as the number of F-T cycles increases, both the duration of the AE development stage and the AE energy level decrease.