Hydraulic characterization of an unsaturated pyroclastic slope by in situ measurements

Full understanding of slope failure conditions in an unsaturated pyroclastic slope needs sound analysis of groundwater flow and hence proper hydraulic soil characterization. In order to explore the hydraulic hysteretic behaviour of pyroclastic soils and their ability to interpret site behaviour, in this paper pairs of water content and matric suction measurements recorded at the same depth in surficial layers of an instrumented unsaturated pyroclastic slope are compared to a number of retention curves obtained in the laboratory. A theoretical interpretation of the observed behaviour in situ and in the laboratory is proposed.