Fluidization Response of Sediment Bed to Rapidly Falling Water Surface

Abstract

A strain-based criterion for sediment fluidization under transient pressure loading is presented. The criterion predicts that fluidization can be spontaneous, as opposed to incremental, and that it is triggered by a lowering—rather than a buildup—of the pore pressure. The criterion is examined and verified experimentally. A dam break is simulated in a laboratory flume, and a sediment bed is included in the half of the flume initially containing water. Both visual observation and extensive pressure measurements within the bed indicate the occurrence of a massive fluidization failure throughout the entire depth and length of the bed. The fluidization failure is shown to occur on an extremely short timescale. The results from several successive runs, allowing the bed to consolidate overnight between runs, demonstrate the tendency of a bed to repeatedly refluidize.