Experimental Study on Crack Propagation in Fractured Rock Masses with Varying Dip Angles

Anisotropy of joints in rock masses leads to differences in their mechanical properties, with joint inclination being an important influence. An accurate description of the effect of joint inclination on the cracking behaviour of rock bodies is essential for engineering disaster prediction and prevention. In this paper, the preparation of rock-like specimens containing varying dip angles is based on Monte Carlo theory and 3D printing technology. The strain field evolution characteristics and mechanical anisotropy of the jointed rock masses were quantitatively analysed using uniaxial compression test and digital image capture (DIC) technology. The effects of different inclination joints on the deformation field and crack extension behaviour of the rock masses were investigated. A damage ontology model of the rock masses considering the initial damage was established. The results reveal that the strain concentration is more likely to occur at the tips of joints with larger inclination angles and closer to the free surface of the specimen. Strain concentration occurs earlier in complex joint networks where local joint densities are smaller. Further, a method is proposed to quantitatively study the effect of joints on the strain field evolution characteristics of the rock masses based on intelligent image recognition techniques. It is found that joints with dip angles from 30 to 90° have a greater effect on the strain field. 15–60° dip angles have a greater effect on the crack extension paths of the specimens. The 15°, 30°, 60° dip joints have the most significant effect on the fracture characteristics combined with the results of strain field evolution and crack extension paths of the specimens. These are the key inclination angles affecting the fracture behavior of rock.