Modeling landslide triggering in layered soils

Abstract

The Flemish Government (represented by AMINAL; Administration of Environment, Nature, Land and Water management) commissioned a research project to study the triggering of landslides in the Flemish Ardennes. A few representative sites subject to landslides were studied from a geotechnical point of view. Several sites were selected for geotechnical calculations in order to predict the conditions necessary to trigger a landslide and to verify the predictions with the observations on site. Two of those sites are discussed in this paper. A hypothetical collapse mechanism, possibly responsible for many landslides in the Flemish Ardennes, was numerically verified. The presence of a sand layer (high water permeability) between two clay layers (low water permeability) causes the building up of pore water overpressures, decreasing the effective stresses, eventually resulting in the uplift and/or collapse of the slope. The understanding of the mechanisms responsible for the studied landslides resulted in specific recommendations to prevent future landslides on these sites, but also on similar sites in the region.