A Fully Coupled Analysis Procedure for Dynamic Behavior of Unsaturated Soils

A fully coupled analysis procedure for dynamic analyses of unsaturated porous media is presented. The analysis procedure is based on the finite element implementation of the governing equations derived utilizing the Theory of Mixtures with Interfaces (TMI). TMI explicitly considers the interfaces existing between various bulk phases in a multiphase porous media such as the contractile skin between the pore water and the pore air in an unsaturated soil. The resulting computer code, U_DYSAC2, is used to predict the behavior of an unsaturated kaolin embankment subjected to base shaking and the results are compared with the saturated soil behavior. Unsaturated soil embankment is shown to behave more rigidly than the saturated embankment resulting in lower displacements and higher accelerations. U_DYSAC2 also predicts increase in pore water and pore gas pressures during shaking. The results presented show that it is possible to economically design an unsaturated soil structure for seismic loads using a fully coupled analysis.