Density-dependent hydromechanical behaviour of a compacted expansive soil

To further our knowledge of the coupling between the hydraulic and mechanical behaviours of the swelling soils, this paper presents an experimental study on a bentonite/silt mixture using an osmotic odometer. A loading/unloading cycle was applied to samples with different initial dry densities (1.27, 1.48, and 1.55 Mg m− 3) at different constant suctions (0, 2, and 8 MPa). We noted that the initial state of the soils after compaction significantly influenced the values of the apparent preconsolidation stress p0(s), the virgin compression index λ(s), and the elastic compression index κ.These experimental results provided a sufficient database to interpret the mechanical behaviour of the swelling soil and define three yielding surfaces:–the suction limit between micro- and macrostructure (sm/M) and the suction limit between nano- and microstructure (sn/m), which depend completely on the soil fabrics and the diameter separating the nano-, micro-, and macrostructure,–the Loading Collapse (LC) curve, representing the preconsolidation stress variation as a function of suction,–the Saturation Curve (SC), representing the variation of the saturation stress (Psat) as a function of suction.In general, we can state that the increase of compaction pressure unified the LC and SC surfaces and decreased the (sm/M) value without modifying the (sn/m) value.