Finite element model and simple method for predicting consolidation displacement of soft soils exhibiting creep underneath embankments in 2-D condition

Abstract

How to predict the long-term deformation of natural soft soils under embankments has been an important yet challenging issue in geotechnical and transportation engineering. The major difficulties lie in consolidation analyses of thick soil layers, modelling of the nonlinear time-dependent stress–strain behaviour of clayey soils, and proper determination of soil parameters. While finite element (FE) software has great advantages and wide applications in consolidation analyses, development of reliable simple methods, which can be conveniently used by engineers, is also needed. In this paper, both a fully coupled FE model and a simplified Hypothesis B method are developed and applied for long-term deformation analyses of two test embankments on the multi-layered Malaysian marine clays. FE simulations are conducted using PLAXIS with a nonlinear 3-D elastic visco-plastic (3-D EVP) model. A series of parametric studies are carried out on the influences of soil parameters and modelling techniques using this FE model. A simplified Hypothesis B method with the nonlinear 1-D EVP model and modifications for 2-D stress diffusion and buoyancy effects is derived and applied for estimating the long-term consolidation settlement curves of the two test embankments. It is found that the fully coupled FE model with the nonlinear 3-D EVP can simulate the long-term embankment displacements with good agreement with measured data. Parametric studies indicate that using averaged soil indices and updating static pore pressure have significant contributions to the accuracy of simulations. The settlements calculated by the improved simplified Hypothesis B method are found in close agreement with FE simulation results and measured data.