Stability Analysis of Seawalls under Large-Amplitude Nonbreaking and Breaking Wave Propagation Conditions

This study explores the stability of seawalls by employing two distinct water wave conditions: (1) large-amplitude irrotational water wave generated by solving a global bifurcation problem and (2) plunging breaker modeled using the analytical solution of the Green–Naghdi equation in Camassa–Holm scaling. This work is important because, in traditional design approaches of seawall structures, stability analysis is carried out through analytical or empirical formulations that have inherent limitations in accurately representing complex wave–seawall interactions under extreme conditions. Although recent advancements in numerical techniques, such as the Eulerian–Lagrangian (MEL) scheme and smooth particle hydrodynamics (SPH), enable accurate modeling of such interactions, they are mathematically rigorous and computationally intensive. Moreover, the interaction between large-amplitude traveling water waves (derived from global bifurcation solutions corresponding to maximum wave amplitudes) and seawall structures remains largely unexplored in the literature. In the current study, finite difference method (FDM)-based numerical techniques are applied to analyze the considered wave conditions and obtain the corresponding wave forces and overturning moments on the seawall structure. Factors of safety against sliding and overturning of the seawall are evaluated for seawall thickness ranging from 2 to 15 m. These factors of safety obtained from the numerical schemes are then compared with those derived from existing wave force formulations. Results indicate that for the wave conditions examined, seawalls with thicknesses of at least 7.5 m for large-amplitude traveling waves and 10 m for plunging breakers are observed to be safe, in accordance with various national guidelines. Further, the safety factors vary with the method used to estimate wave forces and overturning moments on seawalls, differing by up to 17% for large-amplitude traveling waves and 33% for plunging breakers relative to those obtained using the numerical schemes. This underscores potential limitations of traditional design methods and the need to incorporate advanced wave modeling techniques to improve seawall resilience and reliability.