Dynamic Analysis of Unsaturated Soil-Pile System Using Simplified Finite Ele- ment Formulation

摘要

The set of governing differential equations for the dynamics of unsaturated soil in its full form is complex and highly nonlinear. Obtaining solutions to real world problems has been a difficult task even with a simple linear elastic material model. In this study, a simplified formulation that is computationally efficient is developed for the dynamics of unsaturated soils by neglecting the relative acceleration and velocity terms of water and air phases at the governing equation level. As the viscous damping matrix does not appear naturally at the governing equation level in the simplified formulation, an external damping in the form of Rayleigh's viscous damping is incorporated to enhance the model's predictive capability. The new formulation is then used to investigate the effects of initial degree of suction on the computed surface spectral accelerations and effect of soil-pile interaction. The analyses reveal that the simplified finite element formulation with Rayleigh damping improves the prediction of the dynamic behavior of unsaturated soil and soil-pile system.