Replication of internal defects and investigation of mechanical and fracture behaviour of rock using 3D printing and 3D numerical methods in combination with X-ray computerized tomography

It is difficult to accurately visualize internal structure and characterize progressive fracture process during rock failure due to the heterogeneous and opaque features of rock. This paper focuses on providing two methods, i.e., 3D printing (3DP) and 3D numerical modelling, to replicate internal defects and study the mechanical and fracture behaviours of rock in combination with X-ray computerized tomography (micro-CT). On one hand, Stereolithography 3DP combined with the X-ray micro-CT and 3D reconstruction techniques were applied to replicate natural volcanic rocks using 3DP resin. Uniaxial compression and Brazilian disc tests were, subsequently, performed to characterize and visualize the mechanical and fracture properties of the 3DP rock. On the other hand, the digital image processing technique was adopted to integrate the microstructures of the natural volcanic rock into the rock failure process analysis code (RFPA3D-digital) for characterizing the failure behaviour of rock under uniaxial compression and tension. The results showed that both the 3DP samples and the 3D numerical models can successfully replicate the internal defects and micro-structures identical to those of the natural prototype volcanic rock. The mechanical properties of the 3DP samples and the 3D numerical models, including compressive and tensile strength and the Poisson's ratio, and fracture properties are testified to be similar to those of the prototype rocks. Visualization analysis of the progressive fracture process demonstrated that the initial internal voids and cracks dominate the spatial fracture evolution and failure patterns within the rock. The proposed methods provide a promising means to quantify, replicate and visualize the pre-existing defects and mirco-structures, and to understand their influences on the mechanical and fracture behaviour of rock under different loading conditions, facilitating better understanding of failure mechanism of rocks.