Seepage Analysis of Orthogonal Shear Cracks in Granite Based on Fractal Theory

Compression shear failure of rock is a common failure mode in engineering, and there are often complicated seepage phenomena in its shear crack. Due to the anisotropic and irregular rough cross-section on both sides of the natural crack, the experimental study of rock seepage is difficult to operate. In order to study the microscopic seepage characteristics of rock cracks, granite crack specimens were prepared through shear experiments. The data was obtained by scanning the section with laser and imported into MATLAB software to reconstruct the three-dimensional section and crack opening model. In view of the difficulty of observing the microscopic characteristics of rock seepage flow, in this paper, the Reynolds equation of rock fracture flow considering the dynamic effect of boundary is derived, and under the condition of the definition of Reynolds equation theory, based on the advantage of fractal geometry for irregular cross-section, the relationship between flow velocity, permeability and simulation scale is studied by using COMSOL simulation software. The results show that the granite cross-section has a good statistical self-similarity feature, and the fractal matrix mesh covering the fracture surface can well express the feature of the fracture surface; The roughness of the fracture surface has a positive correlation with the fractal dimension. The larger the fractal dimension, the greater the roughness of the fracture surface, which verifies the reliability of the fractal dimension to describe the roughness of the section. There is a positive correlation between the scale-up of the simulation and the velocity of the micro-research points, and the permeability of the model; The feasibility of the fractal percolation model is investigated and the general suggestions for simulating scale are given. Some of the results of this study can be used for reference in the analysis of seepage characteristics of fractures in rough rock mass.