Elastic Visco-plastic Consolidation Modelling of Soft Clays Improved by Geosynthetic Vertical Drains

In this paper, an elastic viscoplastic (creep) model is incorporated into the consolidation equation to calculate settlements and excess pore pressures. A finite difference formulation for fully coupled axisymmetric consolidation is adopted to model both vertical and radial consolidation of a multi-layered soil. The effect of smear, non-linear stiffness and varying soil permeability with void ratio can be included in the analysis. The formulation is easily executed in an electronic spreadsheet such as Excel, and it is then validated by existing solutions. Finally, the analysis of a selected case history employing the writers’ formulation is employed to analyse an embankment constructed on the Sunshine Motorway, Queensland, Australia stabilised with geosynthetics vertical drains. The embankment behaviour is analysed by the authors using an elastic viscoplastic model and compared with the field data. The analysis of this case history verifies the improved accuracy of the predictions due to creep effects, in contrast to the conventional predictions which disregarded creep.