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In a self-developed continuum–discontinuum method that considers the internal cracking of quadrilateral elements, the computational domain is divided into quadrilateral elements with high accuracy. After cracking, the cracks propagate along the boundaries of the elements and the diagonal lines of the quadrilateral elements. Deformation, cracking, and contact of rocks can be simulated using this method. For Brazilian disc rock specimens, the rapid increase of tensile crack segments corresponds to a rapid decrease of the load. Compared with the original method, crack propagation is smoother in the improved method. This is because the propagation paths of cracks are fewer in the original method, and the propagation of cracks is hindered. For uniaxial compressive rock specimens, when two shear cracks intersect, one crack may dominate, forming a main crack, and its direction is consistent with the theoretical direction obtained using the Mohr − Coulomb criterion. For the cavern surrounding rock models, some long and narrow shear cracks appear in the surrounding rock, and their shapes are like logarithmic spirals. An interval exists between the shear cracks, and the more to the interior of the surrounding rock, the larger the interval between cracks. The higher the hydrostatic pressure, the faster the shear crack propagates and the easier it is to form a shear slip line. With an increase of cavern size, the depth and range of the shear cracks increase. With a decrease of the internal friction angle, the interval between the cracks increases, and the propagation direction of the cracks become more internal.
Bai et al. (Sun,) studied this question.