Stability analysis of vegetated residual soil slope in Thailand under rainfall conditions

Abstract

The effects of climate change including intense rainfalls have resulted in many slope failures. The bioengineering method using vegetation is an environmentally friendly alternative for slope stabilisation. This paper presents the effect of root reinforcement on the stability of vegetated slope under rainfall condition. A transient seepage and slope stability analysis was conducted based on the finite-element and limit equilibrium methods. Field monitoring on a residual soil slope in Thailand was numerically modelled. In transient seepage analysis, the soil-water characteristic curve and the saturated permeability measured from laboratory and in situ tests were used, and the results were comparable with the monitored values from the site. For slope stability analysis, the effective shear strength parameters from direct shear tests were used to model the well-compacted and non-compacted soil slopes. The additional shear strength of soil from the root cohesion was modelled for vegetated soil slope. The results show that the contribution of root cohesion to slope stability was more significant for the non-compacted soil condition than for the well-compacted one. Both modelled and monitored pore-water pressure reached the highest values about 1 d after the daily rainfall had reached its peak. This finding has a significant implication for landslide warning based on rainfall.