Co-effects of bedding angle and moisture condition on generalized mode III fracture behavior of sandstone: Insights from acoustic emission localization and 3D scanning reconstruction

The generalized mode III fracture mechanism of edge-notched disc bend sandstone specimens exhibiting anisotropy—characterized by bedding planes at various angles—under different moisture conditions (dried, natural, and saturated) was analyzed using acoustic emission localization and three-dimensional scanning reconstruction techniques. The results indicate that the peak load, stress intensity factor, and energy dissipation of the specimens are significantly influenced by both bedding angle and moisture condition. With increasing bedding angle, the peak load, stress intensity factor, and fracture energy exhibit an overall decreasing trend—first decreasing and then slightly increasing. As the bedding angle increases from 0° to 60°, the peak load, initial fracture stress intensity factor, peak load stress intensity factor, and peak load fracture energy of the rock specimens under the natural condition decrease by 22.8%, 23.5%, 19.5%, and 36.7%, respectively. The presence of water within the rock weakens the peak load and stress intensity factors, and reduces the energy required for fracture. Additionally, water weakens the influence of bedding to some extent. In terms of crack network morphology, cracks tend to propagate preferentially along the bedding planes. Specimens with higher moisture content exhibit larger crack initiation angles and higher fractal dimensions.