PROCESSES OF INTERNAL EROSION, CAVITY FORMATION AND COLLAPSE BEHIND COASTAL STRUCTURES UNDER CONTINUED ACTIONS OF RAINFALLS AND OVERTOPPING WAVES

Abstract

 Cavity collapse caused by internal erosion of backfilling sand has occurred frequently at the back sides of seawalls and quaywalls worldwide. Rainfall and overtopping wave have been considered as external forces that cause such cavity collapse, but they have not been fully investigated. In this study, we investigated in detail the processes of internal erosion, cavity formation and collapse under continued actions of rainfalls and overtopping waves by conducting prototype-scale experiments. The results demonstrate that the collapse of the cavities developed by wind wave-induced internal erosion of backfilling sand was caused by a decrease in suction accompanied by the rainfalls or overtopping waves.