The Strength and Macro-mesoscopic Fracture Characteristics of 3D-printed Rock-like Specimens with Internal Parallel Joints

摘要

The internal parallel joints weaken the rock mass and they are more difficult to be studied than the exposed joints. The intact specimen and internal parallel four joints (IPFJ) specimen were prepared by 3D printing for the uniaxial compression. According to the macro-mechanical parameters of the intact specimen, the apparent fractures, and internal 3D fracture modes obtained by computerized tomography technology, the Particle Flow Code 3D (PFC3D) was used to study the strength properties, 3D fracture modes, and macro-meso evolution mechanism of specimens with IPFJ under uniaxial compression. It was found that the apparent macro fractures are initiated at the yield point of about 90 of the peak stress in 3D similar to 2D. However, the stress of inner initial fracture is approximately 30 of the peak stress due to the strike discontinuity of joints in 3D. The stress intensity factors at the inner and outer edges of the joints are influenced by the adjacent joints leading to four fracture modes. Finally, a small number of tensile micro-cracks on the propagation path cause a large number of shear micro-cracks based on the force chain analysis.