An Experimental Study on the Wave-Induced Topographic Change in Artificial Shallows: Focusing on the Effects of Pore-Water Pressure on Sediment Transport

Abstract

Dredging to maintain channels and berths produces large volumes of sand that need to be appropriately disposed of or used. The construction of artificial shallows and tidal flats has attracted attention as a way of effectively using dredged sand. However, there is still an issue to be resolved in that dredged sand with its fine sediments is vulnerable to wave action. In this study, the wave-induced topographic change in artificial shallows composed of fine sand was examined experimentally for bottom flow velocity on its surface and pore-water pressure on its surface layer. Experimental results showed that the relative vertical effective normal stress ratio calculated from pore-water pressure was negatively correlated with the signed Shields parameter defined as positive landward. Its relationship was unchanged despite a change in the surface profile of the shallows, implying an acceleration in seaward sediment transport and a reduction in landward sediment transport, regardless of the topographic change in the shallows. Furthermore, a signed Shields parameter modified to consider the effects of pore-water pressure gave a reasonable evaluation of the trend in the sediment transport. From these results, it was demonstrated that the effects of pore-water pressure must be considered when discussing the sediment transport.