Abstract：The influences of pre-existing crack geometrical position and matrix material mechanical properties on crack propagation and coalescence are studied using self-developed numerical tool EPCA2D. The weak cell element is used to represent the pre-existing cracks in rock specimens. The mechanical parameters of the cell element of rock matrix are assigned values by using Weibull¢s distribution to reflect the heterogeneity of rock bridge as a part of rock matrix. The pre-existing crack and the rock matrix conform to the perfect elastoplastic and elasto-brittle-plastic constitutive relation respectively. Using this method，the failure processes of rocks with two or three pre-existing cracks are simulated；and the phenomena of crack initiation，propagation and coalescence are well reproduced. It is concluded that the geometry of pre-existing cracks has great influence on the crack propagation and coalescence. At the same time，by considering different rock matrix properties，the failure patterns of rocks with different spatial random distributions of mechanical properties and different frictional angles etc. are numerically investigated. It is found that the crack propagation and coalescence paths are strongly dependent on the mechanical properties of materials，which can explain the reason why there exists diverse crack propagation paths in experiment.
