Effect of Confining Pressure on the Fracture Mechanical Properties of Multi-Particle Sandstone

Mechanical properties and the rupture process of rock materials are critical issues for mining engineering that influence efficient ore mining. It, however, may cause energy-saving and emission reduction in the specimen by analyzing the stress and strain distribution and exploring ultimate failure mode. Investigating the mechanical properties and the rupture process in multi-particles is significant to rock fracture mechanism and explore the high-efficiency energy-saving. In this study, the inhomogeneity and irregularity were considered by using digital image processing and rock surface image of vectorization conversion. The effects of different confining pressures on multi-particle effective elastic modulus, fracture characteristics, and acoustic emission characteristics are systematically investigated and analyzed. The intrinsic strength is indicated and is the quantitative description by Mohr-Coulomb and Hoek-Brown strength criterion. The results demonstrated that samples exchange brittleness-ductility-hardening with the confining pressure increases. Furthermore, shear failure of point of contact between particles causes the multi-particle specimen failure, broken sequentially. Significantly, the crack transfixion area does not materialize at the peak of the stress-strain curve. Without confining pressure, the meso-heterogeneity contributes significantly to control the micro-mechanical behavior and the macroscopic response, and the lateral confining pressure restricts the crack propagation.