Characteristics of Copper Tailings in Direct Simple Shearing: A Critical State Approach

Tailings dams, which are storage structures for tailings, often are constructed using the tailings itself. A large number of tailings dam failures have been reported recently, especially due to static liquefaction, and can be attributed to a lack of knowledge of the geotechnical principles to be used and the lack of characterization of tailings as they continuously are produced and used as construction materials. Furthermore, the majority of past research work has been based on triaxial conditions even though it is believed that direct simple shear conditions may better represent the in situ condition of a tailings dam structure. This paper characterized the behavior of a tailings material from a copper tailings storage facility in Canada using the critical state soil mechanics framework using constant volume (undrained), drained, and constant shear drained shearing tests in direct simple shear space. The correlation between a modified state parameter (ψm) with instability state and the flow potential was investigated. Special attention was paid to the behavioral features of the material such as pore-water pressure generation, flow rule and dilatancy, phase transformation, characteristics state, and how they correlate with ψm. The differences in behavior from that of natural granular soils were highlighted.