Abstract:

A great many researches show that the rockburst is related to the mechanical properties of rock. The microcracks in rock mass are formed, expanded and converged which have remarkable influences on the mechanical properties of rock. It may bring about material inferiority and failure. For rock samples under uniaxial compression test, its failure forms include friction slippage, self-similar propagation and crankle expansion of microcracks. Based on the fracture mechanism, these mechanisms of crack propagation situated close to the boundary are studied by theoretical methods with considering three different boundary shapes, i.e. straight, convex and concave. Based on “Interface” element of FLAC simulation technology, the direct numerical simulations of crack propagation are proposed and analyzed. When the crack is situated close to the straight and convex boundary, the beam asymptotic model can be employed to find the crack-free surface interaction. A crack-hole-ellipse interaction model is proposed when crack propagation is near a concave boundary using some simplified methods. The expressions for crack propagation near different boundaries are all derived. The results show good agreement between the numerical and theoretical results. The proposed model can analyze the propagating, interaction of crack with free boundary due to stress distributing of surrounding rock, which can provide new basis for rockburst and theoretical research.

Key words: rockburst, crack nearby free boundary, crack propagation, uniaxial compression, beam asymptotic model, crack-hole- ellipse interaction model