Centrifuge model tests of earthquake-induced submarine landslide

Submarine landslides can cut off seabed pipelines and cables and destroy near-shore structures. Such processes can result in tsunamis, which inflict additional enormous damage in near-shore areas. To date, no modelling experiments have been able to simulate and clarify the conditions necessary for the occurrence of submarine landslides, their gravity flow transition and sedimentation. This study examined the submarine landslide of sand and silty sand induced by earthquake and liquefaction. First, similitude laws pertaining to a submarine landslide in a centrifuge were considered, and the conditions to produce a landslide in a centrifuge were investigated by using various types of test cases. The key factors were the combination of natural water and sand mixed with a significant fine fraction, including the osmotic pressure. In addition to these, the embankment slope failure followed by gravity flow, transition to flow, properties of flow and water-level fluctuation induced by ground failure were examined in detail. The debris flowed not with simple shear, but as a clod of soil similar to fluid, which encourages high-speed flow. Turbidity could be observed above the debris front body, and the fine fraction was deposited on the surface of the debris. The embankment slope failure induced water-level fluctuation.