Experimental data from different testing methodologies on different compacted clayey soils, with dominant bimodal pore size distribution, are presented and analysed, to\ud provide a comprehensive picture of the evolution of the aggregated fabric along hydraulic and mechanical paths. Fabric changes are analysed both from the porous network viewpoint, by means of careful mercury intrusion porosimetry investigation, and from the soil skeleton viewpoint, by quantifying swelling and shrinkage of the\ud aggregates in an environmental scanning electron microscopy study. The consequences of the aggregated fabric evolution on the water retention properties of compacted\ud soils are analysed and discussed. A new model for water retention domain is proposed, which introduces a dependence\ud of the intra-aggregate pore volume on water content.\ud The model succeeds in tracking correctly the\ud evolution of the hydraulic state of the different soils investigated along generalised hydromechanical paths.\ud The proposed approach brings to light coupling between intra-aggregate and inter-aggregate pores in the retention properties of compacted clayey soils. Dependence of the\ud air entry and the air occlusion values on swelling and shrinking of aggregates, besides void ratio, is introduced and discussed.Peer ReviewedPostprint (published version

Abstract. The snowpack is a complicated multiphase mixture with mechanical, hydraulic, and thermal properties highly variable during the year in response to climatic forcings. Bulk density is a macroscopic property of the snowpack used, together with snow depth, to quantify the water stored. In seasonal snowpacks, the bulk density is characterized by a strongly non-linear behaviour due to the occurrence of both dry and wet conditions. In the literature, bulk snow density estimates are obtained principally with multiple regressions, and snowpack models have put the attention principally on the snow depth and snow water equivalent. Here a one-dimensional model for the temporal dynamics of the snowpack, with particular attention to the bulk snow density, has been proposed, accounting for both dry and wet conditions. The model represents the snowpack as a twoconstituent mixture: a dry part including ice structure, and air; and a wet part constituted by liquid water. It describes the dynamics of three variables: the depth and density of the dry part and the depth of liquid water. The model has been calibrated and validated against hourly data registered at three SNOTEL stations, western US, with mean values of the Nash-Sutcliffe coefficient ≈ 0.73-0.97 in the validation period.

[1] Volume changes of natural and compacted soils induced by changes in their water content have many practical implications in the service life of earth dams, river and canal embankments, and waste disposal facilities. An insight into the overall strain response of a clayey soil upon gradual wetting and drying is provided here. Experimental data coming from oedometer and isotropic tests under suction and net stress control are presented for a compacted clay with an initial anisotropic fabric, highlighting the relevant role played by the hydraulic path on collapse, swelling, and shrinkage strains. Irreversible strains could be observed after wetting-drying paths and the subsequent drying-wetting cycle. Both stress and hydraulic histories play a role in the evolution of the directional fabric of clayey soils. The experimental data could be reproduced with a rather simple elastic-plastic constitutive model with a mixed isotropic-rotational hardening, previously conceived for saturated soils. The model is extended to unsaturated conditions by substituting the saturated effective stress with a measure of the average stress acting on the soil skeleton and by introducing generalized hardening rules governed by both plastic strains and degree of saturation. Coupling between the mechanical and the hydraulic behavior is provided by the water retention curve, in which degree of saturation is adopted as a useful measure of the soil water content.Citation: Romero, E., and C. Jommi (2008), An insight into the role of hydraulic history on the volume changes of anisotropic clayey soils, Water Resour. Res., 44, W12412,

In comparison with saturated conditions, negative pore water pressures arising from partial saturation increase the available shear strength on a potential slip surface. This additional contribution is lost progressively during infiltration of rainfall, leading to instabilities, sometimes before full saturation is reached. In such cases, reliable prediction of the safety factor may be achieved, by taking the suction history of the soil into account. A combination of field and laboratory tests was carried out recently to investigate the triggering effect of rainfall on shallow slips in alpine moraine slopes. The problem is complicated by the strong heterogeneity of these soils, with particle sizes varying from silts to boulders. The data highlight the influence of suction on the peak shear strength, and allow for the calibration of simple models, which take into account the dependence of shear strength on the saturation degree. An infinite slope stability analysis is performed. The results are compared with the field data from two test sites, where the development of a shallow planar slip in the steeper 42° slope was observed after two days of artificial rainfall. The less steep 31° slope remained stable.