Upslope Failure Mechanisms and Criteria in Submarine Landslides: Shear Band Propagation, Slab Failure and Retrogression

The volume of a submarine landslide is likely to be amplified by shear band propagation along a basal surface or spreading failure extension in the sliding layer. Although the mechanism of translational submarine landslides has been understood using the interpretation of shear band propagation, assessment of the limits of failure extension, either through shear band propagation or retrogressive spreading, remains a challenge due to the diversity of post failure mechanisms. The paper aims to explore all post failure possibilities and quantify failure initiation and extension accordingly, focusing on the upslope conditions. The different failure mechanisms are explored with the aid of the large deformation finite element modeling. Original criteria for scarp position, shear band length at slab failure, retrogression conditions and ultimate spreading limits are proposed, following the process zone approach considering force equilibrium of the sliding mass. Simplified analytical predictions are shown to agree well with the numerical observations. The findings and criteria presented in the study are expected to help assess the ultimate scale of upslope failure in submarine landslides, which is important in determining geohazard zonation of submarine landslides.