Experimental study for the mechanical characterization of Tunis soft soil reinforced by a group of sand columns

An experimental investigation has been conducted to study the mechanical properties of remolded Tunis soft soil reinforced by a group of sand columns. The tested soft soil, extracted from the city center of Tunis at a depth of 15 m, has poor mechanical properties, and its moisture-sensitivity is very important. Specimens were initially slurry mixed at 1.5 times their liquid limit. They were then remolded at an initial K0 consolidation path up to a vertical stress of 140 kPa. The holes, initially made in the specimens, were afterwards filled with standard sand which simulated the reinforcing column material. All the reinforced soil specimens were then subjected to consolidated undrained triaxial shear tests with measured excess pore-pressure (CU+u). Three confining pressures of 100, 200, and 300 kPa were applied during the consolidation phase. In addition to the unreinforced control specimen, three different types of reinforced specimens were used, namely, reinforced specimens with a single column, three columns, and four columns. All the reinforced specimens had the same area replacement ratio. The test results have shown that the number of reinforcing columns has a significant effect on the mechanical characteristics of the reinforced soft soil.