Finite element simulation of an excavation-triggered landslide using large deformation theory

Abstract

Numerical simulation of an excavation induced landslide in a strain softening material is presented and the results are compared with field measurements. The simulation is based on the methodology proposed to estimate the post-failure deformation of slopes in strain softening materials. The method includes: a) the Updated Lagrangian formulation which is essential in capturing the changing geometry and configuration of the slope during failure, b) a strain softening constitutive model which enables simulation of the progressive failure mechanisms, c) a stable solution scheme to prevent problems associated with numerical convergence in strain softening materials, and d) the h-adaptive mesh refinement technique to prevent excessive distortion of the finite element mesh due to large deformation and to increase the accuracy of the numerical solution.For the slope considered here, it is shown that failure initiated due to the excavation at the toe of the slope and propagated upward due to the strain softening behavior of the geomaterials which eventually led to the progressive failure of this slope. The failure surface is mainly within a thin layer of soil with substantial strain softening behavior but propagates to the surrounding soil as the excavation proceeds. The predicted crest settlement, toe movement, and deformed shape of the slope are lower than the observed behavior of the slope. However, the numerical analysis clearly predicts the triggering factor and the failure mechanism of the landslide and the impact of the large deformation of the soil mass on the houses at the toe of the slope.