Numerical Study On The Influence Of Rock Structural Surface Morphology On Shear Properties

The rock mass is a combination of rock and structural surfaces. Structural surfaces usually determine the physical, mechanical properties and stability of rock mass. The shear strength and failure types of structural surface are closely related to surface morphology characteristics. Due to technical limitations, it is difficult to obtain the mesocharacteristics of structural surface with different morphology characteristics in the process of shear at the present stage. In this paper, the effects of irregular and regular saw-tooth structural surface morphology on shear properties were studied with the help of the FLAC3 D finite difference software.For shear behaviors of irregular structural surfaces, this study adopted moving average process(MA model) to simulate ten surface curves of irregular structural surfaces. The joint roughness coefficient JRC and the fractal dimension D of each shape curve were calculated, and the relationship between joint roughness coefficient JRC and fractal dimension D was established. Three-dimensional numerical models of structural surfaces with uniform width were established based on the above shape curves and the numerical simulation of direct shear tests of structural surfaces were carried out. The macro- and meso-mechanical characteristics under different roughness and normal stress conditions in direct shear test in the process were obtained. By comparing the shear strength of numerical simulation with the results of JRC-JCS model, it was proved that the numerical simulation was reasonable. Based on the correlation between joint roughness coefficient JRC and structural surfaces shear strength and the relationship between JRC and fractal dimension D, the shear strength formula of fractal dimension D was deduced.For the study of shear properties of regular saw-tooth structure, with consideration of the acoustic emission simulation program, direct shear tests of regular saw-tooth structure with different rolling angles were simulated in this paper. Based on the acoustic emission characteristics, the evolution of the displacement field and the damage process in the direct shear tests were studied. According to the different mechanical properties and characteristics, the failure modes could be clarified as sliding-up mode, shearing-through mode and sliding-shearing mode. The characteristics of the sliding-up mode and the shearing-through mode is that stable sliding occurred after the peak shear stress. However, the sliding-shearing mode has obvious stick slip phenomenon.The range of rolling angles and normal stress for different failure modes were determined on account of the features of stress and strength. A piecewise linear formula was established for the shear strength.