EARTHQUAKE-INDUCED SUBMARINE LANDSLIDES IN VIEW OF VOID REDISTRIBUTION

摘要

Submarine slides occurring near-shore in non-cohesive sandy deposits are first discussed in view of void redistribution effect. Model tests demonstrates that formation of water film beneath silt seam plays a key role in liquefaction-induced sliding failure in gentle slope.Considering that soil deposits are naturally stratified with sandwiched low permeability seams, it seems quite reasonable to recognize the water film effect as a major mechanism for seismically induced submarine slides in gently sloped sandy sea-bed near coasts.Analogous void redistribution effect on the submarine slides occurring in clayey sea floor far from coasts is then studied by cyclic loading tests to find out large volumetric strain after strong cyclic loading. Simple consolidation plus seepage analysis considering the earthquake-induced large volumetric strain indicates that excess pore water may accumulate beneath less permeable seams sandwiched in relatively permeable clayey layer, possibly causing delayed shear strength reduction due to excessive swelling just beneath the seam.