Wave-Induced Erosion and Recession in Densified and Low-Fines Sandy Bluffs: A Comparative Study

This study examines hydrogeotechnical processes governing sandy beach-bluff recession under wave action, emphasizing material composition effects. Flume experiments compared large-scale bluffs composed of densified sand (Case 1) and sand with 5% clay (Case 2). By analyzing bluff profile changes, pore-water pressure responses, and moisture content variations, the study quantifies how material properties influence erosion and slope stability. Results reveal distinct behaviors between the cases. In Case 1, rapid infiltration and high permeability led to early saturation, accelerated notch formation, and slope failure at 36 min. In Case 2, cohesive clay properties delayed infiltration, reduced saturation rates, and enhanced stability, postponing failure to 55 min. Pore-water pressure dynamics further highlight these differences, with Case 2 showing gradual pressure buildup and limited drainage compared to the rapid fluctuations in Case 1. The findings underscore the role of fines in moderating erosion, delaying failure, and increasing bluff resilience. This study enhances understanding of how wave action, soil saturation, pore-water pressure dynamics, and hydraulic gradients interact to drive bluff recession.