FULLY-COUPLED HYDROLOGIC/GEOMECHANICAL SIMULATIONS OF SLOPE FAILURE DUE TO RAINFALL INFILTRATION

Slope failure processes involve a tight coupling between unsaturated fluid flow and solid deformation. In modeling these events, however, we may adopt various levels of coupling for the fluid/soil interaction---including uncoupled, iteratively coupled, and tightly-coupled models. In this work we discuss this spectrum of approaches and their respective advantages. We highlight a physics-based, fully-coupled framework we have been developing for modeling hydrologically-driven slope failure. The simulations employ a mixed finite element formulation for variably-saturated geomaterials undergoing elastoplastic deformations. The deforming soil mass is treated as a multiphase continuum, and the governing mass and momentum balance equations are solved in a tightly-coupled manner. We present several numerical examples to demonstrate the key features of this approach, and compare it to traditional limit equilibrium methods. We also discuss the calibration of the continuum model from available field data, as well as how it may be used in concert with larger-scale, regional hazard models. These observations are used to assess the current state of hazard prediction, and to inform the design of future field experiments. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.