Abstract: In order to accurately characterize the deformation and failure modes of prefabricated jointed rocks with different angles under uniaxial compression, a joint model based on 3D printing technology was used to simulate the structural surface in the rock mass. Rock specimens with precast joints with different angles were obtained by pouring cement mortar, and a uniaxial compression test was performed. At the same time, digital image correlation (DIC) technology was used to observe and analyze the process of crack formation, propagation, and penetration in the test specimen. The results showed that as the angle of prefabricated joints increased from 0° to 90°, a decrease followed by an increase in the strength and peak strain of the test piece was observed. Additionally, the elastic modulus of the test piece with angles of 0° and 45° decreased compared to the complete test piece. Based on the DIC test results, the cracks of specimens with angles of 0°, 30°, 45°, and 60° all started from the tip of the prefabricated joint. The crack initiation stress of the specimens with different angles was all consistent with the strength change of the specimens. Under shear stress, the cracks started in the form of shear wing cracks. The cracks of 0° and 45° specimens changed from shear to tensile cracks during the propagation process, and the shear cracks were observed in the specimens of 30° and 60° throughout this process. The crack of the specimen of 90° started from the bottom and tensile failure was eventually witnessed. In this study, an obvious linear positive correlation was found between the cracking angle θ2 of the lower wing and the cracking angle θ1 of the upper wing, and it can be expressed as θ2= 0.828 6θ1 +12.185. As the joint angle increased, the cracking stress decreased first and then increased, which was consistent with the peak stress.

Key words: 3D printing, single joint, uniaxial compression, digital image correlation (DIC) technology, crack propagation, crack initiation angle