3D Digital Analysis of Cracking Behaviors of Rocks through 3D Reconstruction Model under Triaxial Compression

Abstract

The cracking behaviors of rocks significantly affect their mechanical properties. In this paper, a digital analysis approach with X-ray Computed Tomography (CT) imagery is developed to investigate the cracking and mechanical behaviors of rocks. The damage ratio, integrity, and porosity of rocks subjected to triaxial compression are firstly defined based on X-ray CT image and the pixel coordinate system. Then, the evolution process of two-dimensional (2D) and three-dimensional (3D) cracks are studied via 2D CT images and reconstructed 3D fracture models, respectively. Finally, the stress–strain relationship of rocks is simulated by converting the reconstructed models to the finite-element (FE) models. The results show that the rock damage ratio, integrity, and porosity are good factors to describe the cracking behaviors, in which the evolution process of cracks is divided into five stages including: (1) the compaction of initial fissures; (2) the initiation and propagation of microcracks; (3) microcracks coalescence, i.e., the formation and stable propagation of macrocracks; (4) the unstable propagation of macrocracks; and (5) the complete failure of rock samples. The numerical stress–strain curves are in good agreement with the experiment data.