Hydro-mechanical characterization of silty tailings in unsaturated conditions

Tailing dams are characterized by a wide surface exposed to interactions with the atmosphere, the latter governing the position of phreatic surface. Most of previous studies have dealt with the mechanical behavior of the saturated tailings, showing the range of state variables for the occurrence of static liquefaction. The starting point of this research is an available hydro-mechanical characterization of a saturated silty tailing. We aim now at extending this characterization to the unsaturated state. The ongoing study of the mechanical behavior under shearing at imposed water content relies on tests done with a suction controlled triaxial cell, while the hydraulic behavior is studied by means of suction controlled oedometer tests. To account for the heterogenity of the tailing material in situ, the dependency of the water retention relationship on grain size distribution and on initial density / void ratio is under investigation. This preliminary step will allow setting up experiments aimed both at providing a wider hydro-mechanical characterization and an insight on possible onset of liquefaction in unsaturated conditions.