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Different approaches have been used for modeling retention curves. The experimental correlation was first proposed [1-3]. The physical modelling of unsaturated soils is used for this study. The shape of the retention curve is a consequence of physical assumptions. The paper presents a theoretical model based on elastic spherical particle arrangement. Firstly, a uniform model is presented with a single diameter of soil particle. The second step extends the use of the model to graded soils. The model uses only physical parameters easy to measure. The model is compared with the experimental retention curve of two different samples, the Livet-Gavet loam (1.61m-3mm) as paste and the Gavet sandy loam compacted with 85 falls per layer of Proctor weight. It shows its ability to model the experimental curves. It is of great interest for engineers as it uses only physical parameters. It gives a direct determination of the retention curve along the wetting path and along the drying path. It shows also the importance of adsorbed water to describe the retention curve.

This paper presents, an in situ monitoring of the behaviour of a partially saturated soil, subjected to an unloading stress path resulting from excavations. The study case is a 30m deep excavation for the construction of a metro station, The aim of the study is to monitor the evolution of displacements and pore pressure during and after the different stages of excavation. The monitored soil is an expansive marl. The first results have been collected and analysed. Nevertheless the monitoring system should remain in place for a few years.

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