Large-Scale Flume Investigation of Pore Water Pressure Evolution under Wave–Soil–Structure Interaction

This study presents results from large-scale wave flume experiments investigating pore water pressure response under solitary wave impact for both free-field (without structure) and soil–foundation (with structure) conditions. Tests were conducted under varying wave heights and foundation embedment depths. Pore pressure sensors were embedded in sandy soil at varying depths and lateral locations. The study evaluates the evolution of excess pore pressure and seepage gradients relative to established seepage and liquefaction criteria. Under both testing conditions, neither excess pore pressure nor vertical seepage pressures exceeded the critical threshold. When testing the soil–foundation case, increasing wave height at constant embedment depth caused downward seepage at shallower depths, but resulted in upward seepage at deeper layers. Increasing embedment depth further reduced upward-directed seepage pressures, particularly beneath the foundation, while location-dependent responses persisted elsewhere. In the free-field condition, wave impact generated positive excess pore pressure peaks followed by accumulation due to rundown effects. Higher wave heights led to greater excess pore pressure and seepage pressure amplitudes, with responses attenuating with depth. Although liquefaction was not observed dominantly, structural instability was likely influenced by a combination of high wave loading and the development of upward-directed seepage beneath the foundation. These findings provide mechanistic insight into the wave–soil–structure interaction and offer a large-scale experimental benchmark for future numerical modeling.