FLUIDIZATION RESPONSE OF SEDIMENT BED TO RAPIDLY FALLING WATER-SURFACE

A strain-based criterion for sediment fluidization under transient pre ssure loading is presented. The criterion predicts that fluidization c an be spontaneous, as opposed to incremental, and that it is triggered by a lowering-rather than a buildup-of the pore pressure. The criteri on is examined and verified experimentally. A dam break is simulated i n a laboratory flume, and a sediment bed is included in the half of th e flume initially containing water. Both visual observation and extens ive 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 s hort timescale. The results from several successive runs, allowing the bed to consolidate overnight between runs, demonstrate the tendency o f a bed to repeatedly refluidize.