Catastrophic failure of submerged slopes in normally consolidated sediments

Abstract

The application of fracture mechanics methods to shear band growth in granular materials requires careful consideration of the elasto-plastic nature of the material behaviour. In this paper, the Palmer and Rice fracture mechanics approach is applied to the problem of catastrophic shear band propagation in a submerged slope built of normally consolidated sediments. This allows for catastrophic (unstable) and progressive (stable) types of soil failure to be properly distinguished. Many submerged landslides are triggered by earthquakes, via the shear strength degradation, due to the excess pore water pressure accumulation. The conventional analysis assumes that the excess water pressure zone develops simultaneously along the entire landslide length, often reaching several kilometres. When a mechanism of the catastrophic shear band propagation is considered, a much shorter excess water pressure zone (e.g. several hundred metres) can still cause a full-scale landslide (often generating a tsunami wave of considerable height). This mechanism also suggests possible measures for mitigation of the landslide hazard.