Volume changes of natural and compacted soils induced by changes in their water\udcontent have many practical implications in the service life of earth dams, river and\udcanal embankments, and waste disposal facilities. An insight into the overall strain\udresponse of a clayey soil upon gradual wetting and drying is provided here. Experimental\uddata coming from oedometer and isotropic tests under suction and net stress control are\udpresented for a compacted clay with an initial anisotropic fabric, highlighting the\udrelevant role played by the hydraulic path on collapse, swelling, and shrinkage strains.\udIrreversible strains could be observed after wetting-drying paths and the subsequent\uddrying-wetting cycle. Both stress and hydraulic histories play a role in the evolution of the\uddirectional fabric of clayey soils. The experimental data could be reproduced with a rather\udsimple elastic-plastic constitutive model with a mixed isotropic-rotational hardening,\udpreviously conceived for saturated soils. The model is extended to unsaturated conditions\udby substituting the saturated effective stress with a measure of the average stress acting on\udthe soil skeleton and by introducing generalized hardening rules governed by both plastic\udstrains and degree of saturation. Coupling between the mechanical and the hydraulic\udbehavior is provided by the water retention curve, in which degree of saturation is adopted\udas a useful measure of the soil water content.
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