Numerical study of Tunis soft soil improved by combined vacuum consolidation and geodrains

This paper aims at presenting a numerical study of the behaviour of Tunis soft soil improved by vacuum consolidation combined with geodrains. An experimental investigation was carried out on reconstituted samples of Tunis soft soil (TSS) initially extracted from the centre of Tunis city at 35 m of depth. Three consolidation tests were carried out in a cell of 126-mm inner diameter and 290-mm height, the first one included a consolidation test by preload stress (q = 100 kPa). In the second test, vacuum consolidation tests (p_v=100 kPa) were performed. The third test comprised a vacuum consolidation test combined with the preload (p_v=50 kPa and q = 50 kPa). Simulation of those tests by the finite-element PLAXIS-2D code was implemented in axisymmetric conditions. Soft soil model was used to describe the behavior of Tunis soft soil (TSS). During this simulation, a parametric study was performed by varying the horizontal permeability k_h of TSS. Then, by comparing the numerical results to the recorded data in laboratory, it has been verified that the numerical predicted settlements are higher than those measured during the performed laboratory tests. Further, numerical results confirmed that when the coefficient k_h increases, the consolidation is complete in a shorter time. This work highlighted the usefulness of combining the vacuum pressure and geodrains improvement techniques to improve the behaviour of Tunis soft soil.