Crack extension at the concrete–rock interface damaged by high-pressure water environment: DIC research

As a weak link in hydraulic structures such as arch dams, the fracture property of the concrete–rock interface is impacted by various factors, including the material properties of the individual constituents and the fracture process zone (FPZ) at the crack tip. Because the heel area of an extra-high dam has been exposed to a high-pressure water environment, this paper aims to investigate the whole fracture process of the concrete–rock interface after the water pressure effect. In this test, the water pressure was set at 0, 1, 2, and 4 MPa, and the crack deformation of the concrete–rock composite beam under three-point bending (TPB) was monitored in real-time by the digital image correlation (DIC) technique. DIC has been discovered to aid in understanding the damage caused by a high-pressure water environment to material properties. The stable crack extension of TPB composite beams after the high-pressure water exposure was greatly limited, and the corresponding crack length was decreased by up to 35%. The FPZ characteristic length was reduced by 19% when exposed to a high-pressure water environment, resulting in a drop in cohesive toughness on the fictitious crack. KR resistance curves for the concrete–rock interface fracture were constructed to consider the damage to material properties and FPZ evolution by high-pressure water exposure. For a reference for fracture analysis in the dam heel of extra-high dams, the calculation model of critical crack size in elastic fracture and the prediction equation of FPZ characteristic length in nonlinear fracture were constructed for a TPB composite beam.