Investigation of stress-wave-induced crack penetration behavior at the rock-Ultra-High-Performance Concrete (UHPC) interface

•The behaviour of cracks penetrating the granite-UHPC interface under stress wave action was investigated.•The crack propagation speed within UHPC, crack penetration interface speed, and crack propagation speed inside the rock using the CPG system were obtained.•Dynamic fracture toughness of the process crack penetration through the granite-UHPC interface was analyzed. The propagation behaviour of initial cracks in concrete penetrating the rock-concrete interface is still unclear. This study investigated the behaviour of stress wave-induced crack penetration through the Ultra-High-Performance Concrete (UHPC)-granite interface and crack propagation speed (CPS) using a combination of the crack propagation gauge (CPG) system and a split Hopkinson pressure bar. The influence of loading rate and UHPC strength grade on the dynamic fracture toughness of the penetration crack entire process was analyzed by experimental–numerical method. The results indicate that the Rock-UHPC interface can suppress the crack opening displacement in UHPC, thereby limiting the CPS. The loading rate significantly enhances the dynamic fracture toughness of the penetration crack's entire process. The interface is the boundary point, and the dynamic fracture toughness at the crack tip shows a trend of first increasing and then decreasing. The increase in concrete strength grade can improve the interface dynamic fracture toughness. Compared to the interface roughness, the enhancement effect of concrete grade on the interface dynamic fracture toughness is one order of magnitude higher. For concrete engineering on rock foundations, increasing the concrete strength grade can effectively prevent the inherent crack defects inside the concrete from expanding into the interior of the rock foundation.