Experimental Program for the Determination of the Saturation Threshold for Brittle Behavior in Loose Sandy Silt Gold Tailings

Tailings storage facilities (TSFs) worldwide have recently experienced a number of failures, with insufficient undrained shear strength identified as a contributing factor in certain instances. The undrained shear strength of tailings is commonly assessed through element testing, such as the triaxial test, typically performed on loose samples under complete saturation. However, a substantial portion of tailings facility deposits often exist in partially saturated conditions. Despite the recognized increase in tailings strength with decreasing saturation levels, the threshold for the potential occurrence of excess pore pressure generation and strain-softening failure remains unclear. This study introduces a triaxial testing program designed to assess variations in undrained (closed system) shear strength for loose samples of low-plasticity gold tailings, prepared at different degrees of saturation using distinct saturation methods to address their impact. The findings reveal that as saturation decreases from complete saturation to partial saturation, both peak and remoulded strength increase, accompanied by a reduction in brittleness. Furthermore, the saturation history of the sample is observed to influence the brittleness of tailings under unsaturated behavior. A methodology to determine unsaturated brittle areas in a TSF is discussed.