Theoretical and Experimental Investigation on the Relationship between Failure Patterns and Shear Strength of Wedge-Shaped Serrated Rock Joints

To investigate the mechanical relationship between failure models and shear strength of rock joints, theoretical and experimental studies were conducted on regular wedge-shaped serrated structural planes. Using the variable cross-sectional beam method, the stress state of the wedge-shaped serrations during shear was analyzed. It was found that wedge-shaped serrations may undergo four failure models: shear tooth cutting, tensile tooth cutting, climbing shear gnawing, and climbing tensile gnawing, and that different failure models can be converted to each other. The sensitivity of parameters (such as normal stress, rock strength, friction coefficient, and the width l and inclination angle i of wedge-shaped serration) was studied. The mechanical and geometric conditions corresponding to the occurrence and transformation of different failure models were determined. Theoretical formulas for the shear strength of wedge-shaped serrated structural surfaces under different failure models were established. The direct shear tests were conducted on red sandstone rock joints with different inclination angles (30°, 40°, 50°, and 60°) under different normal stresses (4 and 8 MPa). The applicability of the proposed theory was verified by the results of direct shear tests, which will lay a theoretical foundation for further exploration of the relationship between failure models and shear strength of natural rock joints.