Translational upper bound limit analysis of shallow landslides accounting for pore pressure effects

Many rainfall-induced landslides are reported to be shallow. Therefore, when regional slope stability analysis, or landslide hazard mapping is carried out, simple approaches, such as the infinite slope model, are often used. However, the infinite slope model is known to underestimate the factor of safety due to the absence of boundary effects. More sophisticated methods that account for the boundary effects at the toe and head of the landslide are much more computationally expensive. In this paper upper bound limit analysis (UBLA) is presented with a novel failure mechanism which consists of a translational parallelogram in the middle slope and two log-spiral components at the slope crest and slope toe to capture the boundary effect. The new approach is derived for a full range of pore water pressure conditions and validated by finite element limit analyses. For shallow landslides the translational UBLA is found to outperform the conventional log-spiral UBLA. The results of a large parametric study using the translational UBLA are then used to develop a novel analytical shallow landslide model which retains the simplicity of the traditional infinite slope model, but yet improves accuracy considerably, making this an attractive alternative for routine analysis such as landslide hazard mapping.