Investigation of preparation of jointed models and the experimental evaluation of mechanical behavior based on 3D printing

The existence and distribution of joint structures dominate the deformation and fracture characteristics. The research on the complex joint network of rocks is crucially significant for the stability analysis of rock engineering. The application of the 3D printing technology provides an efficient approach to the study of the mechanical behavior of jointed rock masses. A 3D printing-based fracture rock mass model preparation method was proposed to study the influence of the fracture network on the jointed rock mass. The deformation and failure modes of RDFN, DFN, and no-crack models of varied specimen sizes subjected to uniaxial compression were compared and analyzed. The feasibility of the crystal glue and PLA printed materials on the jointed rock specimen was discussed considering the frozen effect on the crystal specimens. According to the result, the PLA material expands under uniaxial compression pressure and extends plastically, which differs from the natural rock specimens. For solid specimens, the failure mode shows an obvious X-shape shear failure. The material of crystal glue shows plastic deformation, which can be used to simulate rock mass in the pre-peak stage. The specimen with cracks exhibited compression-shear failure along an inclined section of approximately 45°. The existence of joint networks decreased the compressive strength, and the compressive strength of the RDFN model was higher than that of the DFN model. An apparent lock segment effect on the compressive shear process of the jointed specimens was obtained. The Size effect of the jointed specimens under the influence of a 3D printed fractures network was examined. The high plasticity of PLA printed material in the post-peak stage limits the feasibility of the 3D printed models. The compressive strength of the solid specimen reaches the maximum value, followed by the rough RDFN specimen, and the straight DFN specimen reaches the minimum. Under the influence of low temperature, the intact model behaved ductile with the compressive strength of the frozen specimen was reduced to about 56.57%. The failure mode of the DFN model was a single-slope shear failure and the hole model was a split failure, which can simulate the fracture pattern of jointed rock masses under the freezing treatment.