Experimental Study on the Mechanical Characteristics of Thin-Bedded Rock Masses Due to Water-Absorption Softening and Structural Effects

The efficient exploitation of deep-buried resources and the penetration of deep tunnels are related to the sustainable development of energy and security, and the stability of the surrounding rock of deep-buried tunnels is an important issue to study. Therefore, the mechanical characteristics of thin-bedded rock masses due to water-absorption softening and structural effects were studied. The results show that the uniaxial compressive strength tends to decrease first and then increase with the rise in layer inclination, and an overall U-shaped distribution is presented. The water-absorption and softening mechanism of slate, which is a typical thin-bedded rock masses, involves water entering the slate along the weak surface of the layer. Then, the expansion of water absorption and the expansion perpendicular to the layer caused by the action of clay minerals causes cracks along the layer surface near the weak surface of the layer, which is macroscopically manifested as a decrease in strength. Through the single weak-surface theory, the layer-inclination range of 25–79° is determined for shear failure. The universal distinct element code can accurately and intuitively reflect the failure mode of rock samples affected by moisture content and structural effects.