Effect of holes on in-plane shear (Mode II) crack sub-critical propagation of rock

Abstract

Shear-box (i.e. compression-shear) test and newly designed electrically conductive adhesive method were used to measure shear crack sub-critical propagation time and rate of sandstone specimen. Different cubic specimens with and without holes were tested to study the effect of holes on the shear crack sub-critical propagation. Numerical and experimental results show that three independent variables of hole, the interval distance S, the distance between the center of hole and the crack tip L, and hole radius R, have different contribution to the ratio of stress intensity factor of the specimen with holes to that of the specimen without hole, K II/K II0. Increasing S and decreasing L and R will result in the decrease of K II/K II0 and help crack arrest. The weight relation of the independent variables for K II/K II0 is S>L>R. The specimen DH3 with the largest value of S and the smallest values of L and R has the longest sub-critical crack propagation time and the smallest sub-critical crack propagation rate. Adding two suitable holes symmetrically to the original crack plane in rock specimen is considered to be a potential method for crack arrest of rock.