Analysis of Initial Crack Propagation and Fracture Behavior at Concrete–Rock Bimaterial Interface

Studying the initial crack evolution and fracture behaviour of the concrete-rock interface is crucial for assessing the safety of engineering structures and disaster prevention work. The safety of engineering structures and disaster prevention work. Three-point bending test was carried out concrete–rock bimaterial composite samples with six interface inclinations using the SANS electro-hydraulic servo universal testing machine system. Additionally, the crack propagation of the specimens was monitored in real-time using digital image correlation technology. The study investigated the impact of interface crack inclination on the fracture mode, load–displacement curve, and fracture energy of the samples. The fracture toughness of concrete–rock composite samples at different interface inclinations was obtained based on numerical simulations, and the relationship between mixed fracture toughness was discussed. The results show: (1) Under different interface inclination angles, the concrete–rock composite specimens can identify three typical fracture modes. (2) The composite specimen exhibits significant nonlinear and softening characteristics in the load–displacement curve. (3) As the interface inclination angle increases from 15° to 90°, the dissipated energy gradually decreases, and the peak dissipated energy also decreases. (4) The interfacial angle has significant influence on the fracture toughness of the composite specimens. As the interface inclination angle increases, the fracture toughness generally improves; while, the differences in mixed fracture toughness between various inclination angles gradually decreases.