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A parametric study of an embankment on soft soils reinforced with stone columns is performed using a computer program based on the finite element method. The cylindrical unit cell formulation is used by modeling one column and its surrounding soft soil with confined axisymmetric behaviour. The computer program incorporates the Biot consolidation theory (coupled formulation of the flow and equilibrium equations) with constitutive relations simulated by the p-q-h critical state model. The following parameters are analysed: the replacement area ratio, the deformability of the column material, the thickness of the soft soil, the deformability of the fill and the friction angle of the column material. Based on the results of this study, a new design method is proposed, relating the settlement improvement factor to the two factors that revealed major influence: the replacement area ratio and the ratio between the deformability of the soft soil and the deformability of the column material.

The studies of excavations in soft clayey soils are normally based on undrained total stress analyses. A better approach consists of taking into account the effects of consolidation during the excavation-bracing process and after the completion of the construction by means of coupled finite element analyses in effective stresses. In this paper, the geotechnical behaviour of a braced excavation in the soft soils of San Francisco (USA) is analysed, both during and after the construction period. Numerical analyses are performed with a finite element program, which incorporates the Biot consolidation theory (coupled formulation of the water flow and equilibrium equations) and soil constitutive relations simulated by the p-q-h critical state model. Numerical results are compared with field results.

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