EFFECT OF DYNAMIC FRICTION ON CRACK SURFACE ON DYNAMIC FAILURE OF BRITTLE MATERIALS

Based on the model of Mode I cracks for rock-like material, a dynamic model for rock-like materials is proposed, which considers the crack concentration, density effect and dynamic friction of cracks. Taking the crack distributed in the square array as an example, the effects of different crack density and friction behavior on the crack propagation process, stress and failure of the specimen are quantitatively analyzed. The numerical results show that: with the increase of crack density, the interaction between cracks increases, the loading stress decreases, and the inertia effect causes the axial additional stress of the specimen to increase. The sliding of the crack surface will reduce the dynamic friction coefficient of the crack surface, promote the crack development, and reduce the strength of the specimen. Compared with the constant friction coefficient, considering the velocity and state-dependent friction model is more reasonable for the sliding process of the cracked surface. The comparison results of dynamic strength factors show that the specimen display an obvious strain rate effect and a dynamic size effect of rock mass strength.