CALCULATION MODEL FOR THE SHEAR STRENGTH OF SOFT-HARD JOINTS BASED ON THREE-DIMENSIONAL MORPHOLOGY AND DILATANCY EFFECT

It is difficult to accurately obtain the shear strength of soft-hard joints of hanging walls and footwalls with different compressive strengths. The shear strength of such special joints cannot be accurately characterized by the commonly used rock joint shear strength models such as the Barton models. We used three-dimensional laser scanning and three-dimensional printing technology to pour artificial joint samples that have the natural joint morphology and the same or different compressive strengths of the hanging walls and footwalls. Shear tests under normal stress were carried out on the samples to analyze the effects of normal stress, three-dimensional morphology and joint strength ratio on the shear strength and dilatancy angle of soft-hard joints. The test results revealed that the shear strength of the joints was positively correlated with the normal stress, joint strength ratio and joint roughness, and that the dilatancy angle was inversely correlated with the normal stress, and positively correlated with the joint strength ratio and joint roughness. By studying the evolution law of the dilatancy angle with the normal stress and the joint strength ratio in the shear process, we established a shear strength model of rock joint with three-dimensional morphology parameters and the joint strength ratio. The reliability of the proposed model was verified by comparison with the Barton model. The model was used to calculate the shear strength of the soft-hard joints in the adit of the unstable slope in the reservoir area of a hydropower station in Yunnan Province. The calculation results were similar to the test values, which proved the applicability of the model.