Modelling combined electroosmosis–vacuum–surcharge preloading consolidation considering large-scale deformation

Abstract

A numerical model, EC3, which was developed to simulate soil consolidation arising from the combined electroosmosis–vacuum–surcharge preloading processes, is presented. The EC3 model improves on its predecessor, model EC2, through incorporating the additional preloading element of vacuum and simulating the consolidation in three-dimensional (3D) space. In EC3, the 3D consolidation was simulated in polar coordinates, which allows for concurrent flows in the radial and vertical directions. The rates of the flows were formulated using the finite difference method. This method enables the model to approximate large-deformation consolidation where the deformation has yielded nonlinear changes in soil properties and nonlinear Darcy fluid flow. The performance of the model was validated against laboratory test results, and the model was applied to example problems in order to optimise the combined consolidation processes. The optimisation results suggested that the combined electroosmosis–vacuum–surcharge preloading process outperforms any two element combination processes with respect to the attained final soil layer settlement when the input parameters remain the same. The presence of a smear zone decreases the consolidation rate but increases the final settlement. The less permeable the smear zone is, the less the attained consolidation rate in the soil layer.