Landslides - Risk Assessment by Modelling the Significant Influences Leading to First-Time Failure

The study of past landslide events shows that natural slopes typicallyfail during or after events of heavy precipitation. Certain areas of slopes appearto fail at random while other areas remain stable. This raises the question,as to whether a better assessment of the risk of a landslide event is possible and how to quantifythe safety against failure. The focus on the development of near-surface landslides qualitatively shows which time-dependent parameters mightplay a role in the course of time until the first slope-failure. The relevant parameters are subsequentlycategorised into different predispositionclasses: minimalto slowly changing predispositions with time (such as soil-grain size distribution, soil-layering, slope angle); significantly changing predispositions with time (such as saturation, peak friction angle) and triggering factors such as heavy rainfall or other impacts. The consideration of all parameters in a singlemodel enables a risk analysis of first-time slope failure as a function of time. This implies that triggering factors maycause slope failure in a situation of higher risk due to stronger predispositions, whereas stronger triggering factors may not cause a failure due to lower predispositions being active in the slope. The predisposition model after Kraettliand Schwarz for the purpose of risk assessment of landslides is introduced. Subsequently, the application is illustrated in the practical example of a landslide site. First results of risk assessment and an outlook for further development of the model are discussed.

Keywords: Landslides, Triggering of mass movements, Strain-softening, Soil mechanics, Unsaturated soil.