SIMULATION OF THE CRACK PROPAGATION FOR THE MODEL WITH A HOLE UNDER DIFFERENT CONFINING PRESSURES BASED ON A CONTINUUM-DISCONTINUUM METHOD

To effectively simulate the transition process from continuum medium to discontinuum medium, a continuum-discontinuum method was developed, which is a combination of the Lagrangian element method, the deformational discrete element method and the fictitious crack method. In this method, the cracking along the diagonal line of the quadrilateral element is taken into consideration. Deformation-cracking processes of the models with a hole under different confining pressures were simulated through this method. The number of tensile and shear crack segments was calculated, and the maximum principal stresses for some elements were monitored. The following results are found. At the low confining pressure, the initial tensile cracks first appear at the roof and floor of the hole, and then they extend towards the top and bottom of the model respectively. At both sides of the initial tensile cracks, remote tensile cracks appear in tensile stress concentration zones, and then shear cracks appear at both sides of the hole; finally, shear cracks go through the model. At high confining pressure, few remote tensile cracks are found, and the dividing line between the stage of remote tensile crack propagation and the stage of shear crack propagation is not clear. The decrease of the maximum carrying capacity is due to shear crack propagation at the both sides of the hole. With an increase of the confining pressure, the number of timesteps of the initial tensile cracks increases, while that of the remote tensile cracks at both sides of the initial tensile cracks decreases and it takes more time for them to appear.