Fracture failure characteristics of shallow coral reef under wave dynamic loading

Abstract

Long-term wave loading is the main cause of destabilization and damage to shallow coral reef near the coast. In this study, the fine-scale damage mechanism and fracture characteristics of reef at a scoured structural surface were analyzed based on fracture and fine-scale mechanics principles to investigate the effect of the number of wave loading cycles on fracture damage to coral reefs. Through indoor hollow torsional shear and Brazilian splitting tests, the deterioration effects of the tensile strength and fracture toughness of reef rock were investigated. Finally, the reliability of the model for simulating the fracture toughness degradation of reef rock was verified by conducting a comparative analysis between the experimental and theoretical results. The results showed that with an increase in the number of wave loading cycles, the fracture control coefficient Qn of the coral reef first decreased, then decreased more slowly, and finally, tended to stabilize. When fracture propagation in the scouring structural plane occurred, the deterioration effect of the wave loading on the fracture toughness of the coral reef limestone was more significant than that of the tip stress intensity factor. Under the same number of wave loading cycles, Qn showed a decelerating decreasing trend with an increase in the effective wave height, and a decreasing and then increasing trend with an increase in the wave period, and the increasing phase is almost linear. The final extension length of the rock at the scouring structural plane of the coral reef is positively correlated with the wave height and has a V-shaped correlation with the wave period.