Numerical and Experimental Assessment of the Sandstone Fracture Mechanism by Non-uniform Bonded Particle Modeling

The cracked chevron notched Brazilian disc method (CCNBD) recommended by the International Society for Rock Mechanics is a major method for measuring the rock fracture toughness. In the rock fracture mechanics, the micro-crack evolution behavior during Mode I fracture is of great theoretical significance. To fully understand the micro-crack evolution mechanism and fracture process zone evolution information of non-uniform sandstone, numerical simulation of CCNBD specimen under Mode I fracture condition was carried out using PFC 3D . Combined with the box fractal dimension theory, the sandstone particle size and mineral composition were considered, and the non-uniform bonded particle model was built. By monitoring the evolution of micro-cracks in the interior and boundary of the cluster, the micro-crack evolution process of the numerical model was obtained. The results showed that the micro-fracture of CCNBD specimen during the cracking process was dominated by weak cementation plane and the contact of interstitial filling particles, while the micro-crack generated between detritus particles mainly concentrated in the CCNBD specimen with the peak stress range of 80–100% and the post-peak failure stage. Combined with the stress field analysis, the Mode I fracture experiment of the bonding between diagenetic mineral particles at the crack tip of CCNBD specimen was dominated by tension, while the bonding between interstitial filling particles is dominated by compression. The micro-crack evolution mechanism of the CCNBD specimen during Mode I fracture was obtained by experiments and numerical simulations. This study is expected to improve the understanding of the unstable fracture mechanism of the fractured rock mass.