Biaxial Compression Containing Closed Cracks A Limited Yanban The Fracture Study

There is a little research on the compound fracture criterion of crack closure state relatively. Closed-crack in the rock plates is a special pure II crack essentially. The paper, which based on fracture mechanics, studied the inclined-crack tip stress intensity factor of the rock mass and its fracture criterion in the theoretical analysis and numerical calculation. The contents included three aspects as follows:(1) On the basis of calculation shear stress factor of infinite width plate with an inclined crack, fomula of the crack shape influencing factor of the inclined closed-crack in the finite rock plates was dedused. Considering different friction coefficients between the upper and the lower surface of closed-crack, we calculated the crack tip stress intensity factor of pure II crack.(2) Adopting ANSYS finite element analysis software, built the finite element 2D model of the rock plates with a closed-crack and determined closed-crack tip stress intensity factor in different angle's crack and in different length's closed-crack and compared with the analytic results.(3) Found the relationship of crack tip stress intensity factor of inclined closed-crack between the rock plates under uniaxial compressive loading and under biaxial compressive loading, built the minimum twin shear stress summation fracture criterion in sameτ_rθ line of inclined closed-crack considering frictional effect and identified the angle for II mode fracture initiation.