Acceleration of the consolidation process of a clayey soil by preloading and vertical drains: field measurements and numerical predictions

The method of preloading associated with vertical wick drains was used to limit settlements of two oil tanks founded on a clayey soil. Monitoring of soil settlements was carried out during the preloading period and the hydraulic leakage test of the tanks. A back-analysis of the behaviour of the foundation soil of one of the tanks was performed and the results of the analysis are compared with the observed performance. Effective stress finite element analyses were carried out using an elastic-plastic rate independent constitutive model with isotropic hardening, capable to reproduce the soil non-linearity. The model was calibrated using the soil stress-strain curves obtained in consolidated undrained triaxial compression tests. Numerical results predicted satisfactorily the observed time-settlement curve at the centre of the tank and the overall field of displacements monitored during the preloading period and the hydraulic leakage test.