Use of bulk embedding cohesive elements to realize bifurcating propagation of rock crack

To investigate the connection and bifurcation problems of the propagation principle and behavior in the whole process of rock crack, bulk insert of cohesive elements between entity elements has been developed. First, it defines what kind of cohesive element is best to be inserted between the model elements. To minimize the influence of embedded cohesive elements on the overall stiffness, K cohesive needs to be far greater than that of the solid elements. Moreover, it is found that if the maximum principal stress criterion is used as the criterion of crack damage initiation and the displacement law is used as crack evolution criterion, the simulation results had the best convergence. Second, it finds a way to insert cohesive elements between all the elements of the model. It is realized by revising the inp file. For a complicated model with many elements, manual revising is difficult. The pattern of inserting cohesive elements in the inp file has been programed such that the inp file can be revised automatically. In Example 1, the three-point bending failure mode of concrete beams has been simulated. The simulated results have been compared with the experimental results so as to verify the effectiveness of the cohesive element in simulating the crack propagation and the correctness of the program for bulk insertion of the cohesive elements. In Example 2, cracking, propagation, connection and bifurcation of cracks in rocks containing inclusions have been simulated, and the tests are being carried out.