Crack growth properties in granite specimens consisting non-persistent joint under punch shear through test

Abstract

Experimental and numerical methods were used to investigate the effect of echelon notchs on the shear behaviour of joint’s bridge area in granite. A punch-through shear test was used to model the granite cracks under shear loading. Granite samples with dimension of 20 mm×150 mm×40 mm were prepared in the laboratory. Within the specimen model and near the edges, four edge notches were provided. Nine different configuration systems were prepared for notches. In these configurations, the length of each notch was taken as 3 cm, 4cm and 5 cm. Assuming a plane strain condition, special rectangular models were prepared with dimensions of 100 mm×100 mm using particle flow code in two dimensions. similar to those for joints configuration systems in the experimental tests i.e. 9 models with different rock bridge lengths and rock bridge joint angle were prepared. The axial load was applied to the punch through the central portion of the model. This testing showed that the failure process was mostly governed by the rock bridge length and rock bridge angle. The shear strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. It was shown that the shear behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the rock bridge angle. The strength of samples decreases by increasing the joint length. The failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods.