Effects of structural plane on shearing behavior of anchored rocks under true triaxial disturbance: Morphology, roughness, and lithology

Rock mass structural planes play a critical role in ensuring the safety and stability of deep underground engineering structures, including roadways, tunnels, and chambers. However, experimental studies on anchored structural planes with varying foliation morphologies, roughness levels, and wall plate lithologies under true three-dimensional (3D) stress conditions are limited, resulting in an incomplete understanding of their mechanical behaviors and failure mechanisms. This study employed a newly developed true triaxial dynamic–static combined shear testing system to conduct a series of true triaxial disturbance shear tests on anchored structural planes in granite, marble, limestone, and sandstone. The effects of foliation morphology, initial roughness, and wall plate lithology on the mechanical behavior and fracture evolution of anchored structural planes were systematically examined, including disturbance shear strength, deformation characteristics, fracture surface morphology, anchor rod deformation, microscopic fracturing mechanisms under shear loading, and failure precursors. The results showed that increases in foliation undulation, thickness, and initial roughness enhanced both disturbance shear failure stress and critical strength, accompanied by an increase in fracture surface roughness. As the wall plate lithology changed from granite to sandstone, the disturbance shear failure stress and critical strength decreased by 48.4% and 49%, respectively. The fracture surface roughness exhibited a generally increasing but fluctuating trend. Lower foliation undulation and thickness reduced the fluctuation intensity of the acoustic emission (AE) b -value, whereas the fractal dimension ( D t ) decreased from 2.6 to 0.5. Furthermore, decreasing the initial roughness from 15% to 5% resulted in an increase in the proportion of shear cracks from 9.55% to 14.73%.