Field monitoring of the water pressure and displacement of a partially saturated expansive marl under an unloading stress path due to deep excavation

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.