A three dimensional (3D) Voronoi tessellations based on Distinct Element Method (DEM) is proposed for simulation of crack initiation and propagation in polycrystalline-based brittle rocks. Damage evolution equations for brittle rocks have been extensively studied in the past. However, the damage model with respect to Mesoscopic Method has not been widely developed due to difficulty of direct observation for microcracks in laboratory tests. The Voronoi tessellation approach which can measure the invisible cracks was firstly utilized to simulate the Uniaxial Tension Test (UTT) in this study. A series of simulated Uniaxial Tension Tests were conducted to investigate the relationships between micro-parameters and macro-response and validation study with laboratory test was also carried out. Moreover, a novel damage model relying on crack initiation and propagation was defined and comparisons of evolution equation between existed models were also conducted to validate the accuracy and robust of the model. A good agreement was found between the simulated results and laboratory observations (e.g. failure modes, peak strength and cracks location). Different methods are proposed to detect the damage thresholds such as crack initiation value (CI) and crack interaction value (CD). Comparisons are also discussed to accurately measure the thresholds values.

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