Three-Dimensional Modelling of Rotational Slope Failures with GRASS GIS

Abstract

Landslides starting from unstable slopes threat people, buildings and infrastructures all over the world and are therefore intensively studied. On the one hand, engineers use sophisticated models to identify hazardous slopes, mostly based on longitudinal sections. On the other hand, less sophisticated infinite slope stability models are used in combination with Geographic Information Systems (GIS) in order to cover larger areas. The present paper describes an attempt to combine these two philosophies and to come up with a spatially distributed, three-dimensional model for slope stability going beyond the widely used infinite slope stability concept. Both models are applied to artificial topographies in order to compare the outcomes of different slip surface assumptions and to benchmark the validity of the infinite slope stability model. It was found out that the resulting factor of safety is highly sensitive to the type of model used and to the slip surface geometry. In complex terrain, the performance of the infinite slope stability model strongly depends on the specific situation, particularly on slope curvature and slip surface depth.