Abstract

Submarine landslides are a major geohazard among worldwide continental slopes, posing significant threats to offshore infrastructure, marine animal habitats and coastal urban centres. This study establishes an original numerical package for time-efficient modelling of the entire submarine landslide evolution covering the pre-failure shear band propagation, slab failure and post-failure dynamics. The numerical scheme is based on the conservation of mass and the conservation of momentum and combines the shear band propagation theory and the depth-integrated method, with the consideration of the drag force from the ambient water. Shear band propagation in the weak layer and slab failure in the sliding layer are controlled by the strain softening and rate dependency of the corresponding undrained strength parameters. The post-failure behaviour in the sliding layer, such as retrogression upslope and frontally confined and frontally emergent mechanisms downslope, is also simulated. The numerical results from the proposed method are comparable to the analytical solutions and the large deformation finite element analysis. Application of this method to a back analysis of the St. Niklausen slide in Lake Lucerne reproduced the observed shape of the mass transport deposits, the position of the main scar and the travel distance. Because of its easy implementation and efficiency, the proposed numerical method for modelling of submarine landslides seems promising for practical applications.

Highlights

  • Submarine landslides are a major natural geohazard commonly occurring in offshore continental slopes

  • This study mainly aims to introduce an original package for modelling the submarine landslides by numerically solving the shear band propagation (SBP) governing equations with the simple depth-integrated method

  • The results from the depth-integrated analysis, in terms of the critical condition for shear band propagation and arrest, and post-failure behaviour, have good agreement with the results from the large deformation finite element (LDFE) analysis and analytical solutions, validating the numerical scheme proposed in the study

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Summary

Introduction

Submarine landslides are a major natural geohazard commonly occurring in offshore continental slopes. If the gradual increase in loading is assumed to occur uniformly along the whole weak layer, the shear band will initiate from the most critical point In this case, the strength reduction during shearing and SBP in the weak layer and global failure in the sliding layer are self-driven and inherently reflected in the constitutive model. The results from the depth-integrated analysis, in terms of the critical condition for shear band propagation and arrest, and post-failure behaviour, have good agreement with the results from the LDFE analysis and analytical solutions, validating the numerical scheme proposed in the study.

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