Numerical Investigation of Wave Overtopping in Impermeable Seawalls Coated with Sand-Based Porous Media

A seawall's structural integrity can be damaged by wave overtopping. To mitigate wave overtopping, this study investigates the effectiveness of incorporating a porous layer into impermeable seawalls. A numerical model wave was developed using a finite volume method and first validated by simulating an impermeable seawall without a porous layer, showing a 90% agreement with laboratory data. Applying a porous sandstone layer on the seaward face of the impermeable seawall followed this validation. A study was conducted to investigate the impact of various characteristics of the porous layer on the reduction of overtopping discharge, including thickness, porosity, and grain size. It was found that increasing the thickness of the porous layer (up to 2 m) resulted in a 60% reduction in overtopping discharge, while all other parameters remained constant. Moreover, increasing the porosity of the sand layer improved the reduction rate by 67%, indicating enhanced energy dissipation and absorption capacities. Using grain sizes of 0.2–1 mm and 2–3 mm reduces overtopping discharge by 35.57% and 66.2%, respectively. The results of this study demonstrate that the proposed approach is a viable and practical method of reducing wave overtopping.