Modeling of Crack Initiation, Propagation and Coalescence in Uniaxial Compression

Summary ?Cracks that initiate from pre-existing discontinuities can link with other cracks or with other discontinuities and produce failure in a rock mass. The Displacement Discontinuity Method (DDM), FROCK, is used in this investigation to model experimental observations on pre-cracked specimens of gypsum. In these experiments two fractures, which were either both open or closed, were placed through the thickness of the specimens, and detailed observations of the cracking process were performed as the specimens were loaded in uniaxial compression. The following aspects are studied for both open and closed fractures: 1) crack initiation stress; 2) direction and propagation of the new cracks; 3) type of coalescence and stress at which it occurs. Modeling is done considering the actual size of the specimens. Relations between the direction of initiation for each type of crack, the orientation of the initial fractures, and the type and coalescence are established. In addition, comparisons between results from experiments and predictions from the model are presented. The numerical results are in agreement with the experiments.