Wave-induced Liquefaction and Sediment Transport in Coastal Environment

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This research project aims at developing an integrated framework by which to describe consistently the processes of wave-induced liquefaction, fluidization and sediment transport that have profound practical implications in coastal environment. The principal results obtained may be summarized as follows :1)Effect of wave-loading history upon liquefaction resistance of sandy sediments ; A series of centrifugal wave tests with carefully designed wave-loading histories showed that re-liquefaction resistance increased significantly due to marked densification that had occurred through "solidification" in the preceding wave-loading stage.2)Development of a computational model for sediment gravity flow ; A three-dimensional analysis procedure for sediment gravity flow (3D-LIQSEDFLOW) has been developed in the research project. The liquefied soil is modeled as a heavy viscous fluid and a soil domain undergoing solidification is described in terms of elastoplastic consolidation theory. The free and solidification surfaces during flowage are traced using a VOF technique, facilitating analyses of a range of moving-boundary problems such as underwater sediment-dam breaking problems.3)Mechanisms of sediment gravity flow and ensuing re-deposition ; The way in which liquefied sediment flows out and comes to a rest, was investigated in laboratory flume tests with a PIV technique introduced. The results clearly demonstrate how the initially fluid-like body of sediment with a high concentration underwent solidification in the course of flowage, eventually coming to an abrupt stop or "freezing".