Modelling of fluidized geomaterials: application to fast landslides

Fast catastrophic landslides cause many victims and important economic damage around the world every year. It is therefore important to predict their path, velocity and depth in order to provide adequate mitigation and protection measures. The distance travelled by these fluidized avalanches is large in many cases, such as lahars in volcanoes. Three dimensional models are extremely expensive, and depth integrated models provide a reasonable compromise between computational cost and accuracy. One important aspect to model is the constitutive/rheological behaviour of the materials. This paper describes both from the solid and from the fluid dynamics points of view models which can be used to describe fluidized soil behaviour. Concerning initiation or triggering, we describe generalized plasticity models for liquefaction and collapse of loose metaestable soils, as these mechanisms are found in many fast landslides. Once the soil has fluidized, we shall describe its rheological behaviour, giving details of how to obtain depth integrated rheological models