Acceleration mechanism of void development in concrete riprap seawalls

Laboratory experiments have been conducted to investigate the acceleration mechanism of the void development in the backfill of a seawall. It is found that the rate of sand leakage is proportional to the air amount in the soil medium. Therefore, the larger void appears to accelerate the further enlargement of the void. Leakage of sand has been found to be closely related to the seepage flow due to the pressure gradient between the soil medium and the water. Therefore, propagation of the wave-induced pressure response influences the leakage of sand. Compressibility and permeability of soil medium have been found to be two significant parameters for the rate of leakage.