Understanding the Damage and Crack Evolution of Coral Reef Limestone Under Stress‐Seepage Coupling: Insights From the Finite‐Discrete Element Method

To investigate the damage and failure behavior as well as crack evolution characteristics of coral reef limestone under stress‐seepage coupling, a damage constitutive model was developed for coral reef limestone subjected to coupled stress‐seepage conditions. Based on the FDEM (Finite‐Discrete Element Method), the mechanical behavior, mesoscopic progressive failure process, and crack propagation mechanisms were analyzed. The regulatory effects of confining pressure and pore water pressure on the mechanical response and seepage evolution of the coral reef limestone were also clarified. The results show that coral reef limestone exhibits pronounced brittle failure characteristics under stress‐seepage coupling. Its mechanical behavior is jointly controlled by confining pressure and seepage pressure: strength and deformation capacity increase with confining pressure but decrease with pore water pressure. The constitutive model developed using the FDEM approach can accurately describe the mechanical behavior of the rock mass under coupled stress‐seepage conditions and shows a high degree of agreement with experimental results. Confining pressure and water pressure have significant effects on the mechanical behavior and crack evolution of coral reef limestone. Under low confining and seepage pressures, cracks primarily propagate linearly in a shear‐dominated mode. As both pressures increase, the failure mode gradually transitions to a mixed tensile‐shear regime, with increased crack density and more complex propagation paths. Eventually, a multi‐branched and multi‐level through‐going failure network forms, resulting in a significant reduction in residual strength. These findings provide theoretical support for stability assessment of underground island engineering and prevention of seepage‐induced geohazards.