Landslides occur when earth material moves rapidly downhill after failing along a shear zone. Debris flows are differentiated from landslides by the pervasive, fluid-like deformation of the mobilized material. Landslides and debris flows threaten lives and property worldwide. Despite the fact that good progress has been made within the last two decades relative to understanding hydrologically driven slope failure, important research has yet to be conducted in 3D physics-based fluid flow and hydrologically-driven slope instability in variably saturated soils.
We are conducting interdisciplinary research focused on a physics-based characterization of coupled hydrologic response/slope stability processes. The modeling approach couples solid deformation with fluid flow processes in variably saturated soils, as well as quantifies the exchange of water between the subsurface and surface continua. The project has two validation components. First, we are testing unsaturated slopes in a 3-m diameter centrifuge facility (maximum radial acceleration = 200g) at the Universität für Bodenkultur (BOKU) in Vienna, Austria. Second, we are analyzing comprehensive and exhaustive data from the Coos Bay experimental catchment (CB1) to test the validity of our formulation for steep hillslopes at the catchment scale. The numerical simulations utilize stabilized mixed solid deformation-fluid flow finite elements employing linear interpolation for the two types of degrees of freedom.