Effect of the density and inclination of joints on the strength and deformation properties of rock-like specimens under uniaxial compression

The effects of the combination of joint density and inclination on the strength and deformation characteristics of rocklike specimens containing open joints were studied by using uniaxial compression tests. The following conclusions were made:with the increase of joint inclination, the stress-strain curve changes from a multi-peak value to a single peak value and the brittleness of the specimen enhances, whereas the ductility of the specimen weakens. The influence of joint density on the unified peak strength is related to the size of joint inclination, and the effect of joint density on the unified modulus shows a "V" shape, namely, the unified elastic modulus first decreases and then increases with the increase of joint density. With the increase of joint inclination, the unified elastic modulus increases gradually and its maximum value, which achieves 70%-80% of the complete specimens' elastic modulus, appears at 90° of joint inclination. The joint inclination is the major influencing factor on the unified peak strength and the unified elastic modulus of the rock-like specimens containing many joints. Further analysis on the test results demonstrates that the transformation law of the relationship between the joint density or joint inclination and the stress-strain curve, as well as the unified peak strength and the unified elastic modulus, is related to the failure process of the specimen. The failure mode of the specimen can be classified into three categories:tension failure, shear failure, and mixed failure.