Hydromechanical behaviour of an expansive bentonite/silt mixture in cyclic suction-controlled drying and wetting tests

To further our knowledge of coupling between the hydraulic cycles and mechanical behaviour of the swelling soils, this paper presents an experimental study on a bentonite/silt mixture using an odometer with suction controlled by the osmotic technique. A loading/unloading cycle was applied to each of the samples at different constant suctions (0, 2, 3 and 8 MPa). Moreover, successive wetting and drying cycles were applied under constant vertical stress at a suction range of 0 to 8 MPa, followed by a loading/unloading cycle at similar suctions (0, 2, 3 and 8 MPa). Finally, the compression curves of the aforementioned suctions with and without the application of suction cycles were compared, so as to analyse the influence of hydraulic cycles on the soil fabric and the mechanical parameters. It is observed that the wetting and drying cycles applied to both the micro- and macrostructure significantly influenced the virgin compression index λ(s), the apparent preconsolidation stress p0(s) and the elastic compression index values κ. However, the hydraulic cycles imposed only on the micro- or macrostructure induce negligible changes in the mechanical parameters of the soil.