Coupled BEM-FEM Fracture Response Analysis of Concrete Gravity Seawall Under Sea-Level Rise and Crack-Face Hydrostatic Pressure

Aging concrete seawalls are increasingly exposed to deterioration and sea-level-rise (SLR)-related hydraulic demands, yet the fracture response of pre-existing water-accessible cracks under combined coastal loading remains insufficiently understood. A MATLAB R2025a-based coupled BEM-FEM framework is developed to evaluate a plain-concrete gravity seawall using linear-elastic fracture mechanics (LEFM) under plane-strain conditions. Quadratic boundary elements represent the uncracked seawall region, while a locally refined Q8 FEM patch with quarter-point elements represents the toe-crack response. Parametric analyses consider self-weight, 25% and 50% backfill-pressure reductions, seawater levels of 1.52, 1.82, and 3.05 m, crack-face hydrostatic pressure, and normalized crack lengths, a/W = 0.1–0.7. Benchmark and mesh-sensitivity studies demonstrate stable fracture parameters. Results show that a/W primarily governs the nonlinear increase in fracture response, whereas crack-face hydrostatic pressure reduces both the closure tendency and the J-integral-based equivalent stress-intensity magnitude, KJ. Elevated seawater levels and backfill reduction exert secondary influences. The toughness-normalized index remains below unity, and crack-face displacement is normal-component-dominant. Independent ANSYS 2021R1 analyses provide trend-level corroboration of reduced equivalent fracture magnitude and closure-directed displacement. Overall, the coupled BEM-FEM framework identifies crack length and assumed concrete fracture toughness as governing parameters for the screened response and provides an efficient numerical approach for coastal concrete fracture assessment.