Abstract: The distribution of flaws in rock has evident influence on the macro-and-microscopic mechanical properties and the evolution of microcracks of rocks. The smooth joint model was adopted to establish the rock model with different inclination angles based on the discrete element method (DEM) for uniaxial compression test. The stress-strain characteristics, microcracks development, distribution of energy dissipation in microscopic scale in the process of compression are studied. Results imply that the inclination angle of flaw is correlated with the stress-strain of the model, and also affects the evolution of microcracks. When the inclination angle of flaw is small, visible tensile cracks develop before peak strength is reached, and the cracks continue to grow after peak strength and other macroscopic cracks appear. On the contrary, when the inclination angle of flaw is large, the microcracks are mostly scattered before the peak strength, and surged to multiple cracks after the peak strength. Energy dissipation rule shows that the energy of rock is mainly stored in elastic energy through parallel bond. In the process of compression, the elastic energy decreases slowly and turns into frictional energy, damping energy and fracture energy. The proportions of such four kinds of energy are roughly equal at failure.

Key words: marble, pre-existing flaw, evolution of crack, energy dissipation, inclination angle of flaw