Quantitative description of fracture behavior and mechanical anisotropy of fractured rock mass: Sand 3D printing and DIC explorations

A complex fracture distribution in a rock mass makes the preparation of a physical sample with fracture networks an important problem in rock mechanics testing. As sand 3D printing offers outstanding advantages in the fabrication of complex structures, it is used in this study. There are a number of 3D printed samples with fracture networks at different rotation angles were prepared. In terms of low dispersion in the geometric and mechanical properties, the possibility of using 3D printing sand samples to reproduce fractured rock mass with high precision was verified. The fracture behavior and the mechanical anisotropy of fractured rock masses were quantitatively analyzed by uniaxial compression testing and digital image correlation method. Dispersion measure of the strain field was proposed as a method for identifying crack initiation, and the variation mechanism of the proposed measure was interpreted. By calculating the displacement vector distribution, it is found that the strain-softening behavior is related to the rock block interlocking. The fractured rock masses exhibit post-peak strain-softening behavior, and the mechanical property (σi, UCS and E) and crack coalescence pattern show obvious anisotropic characteristics. The results show that 3D printing and DIC provide convenience for the quantitative characterization of fracture behavior and mechanical anisotropy of complex fractured rock mass.