Response of dense beach above water tailings to cyclic equipment loading at Syncrude's southwest sand storage facility

Increased pore pressures and softening of dense beach above water tailings were observed at Syncrude when cyclic equipment loading was applied, resulting in stoppage of several reclamation projects and presenting challenges for future reclamation activities. The softening was accompanied by the formation of sand boils and appeared to be a liquefaction type behaviour, although swelling and retention of static strength were also observed.; To study whether it was liquefaction that caused softening, instrumented test areas were softened by equipment and human activities that imparted cyclic loading on a Syncrude site. Analyses of in-situ test data and subsequent laboratory test results showed that the tailings were initially dense of their critical state. This and the stress paths observed during cyclic loading are consistent with cyclic liquefaction. Several controlling factors and potential mechanisms for the observed softening were identified, and the field data was used to develop correlations for other sites and loading conditions.