A Numerical Investigation of the Seismic Response of Tailings Impoundments Reinforced with Waste Rock Inclusions

The rate of failure of tailings impoundments is much larger, by a factor of about 10, than that of conventional water retention dams, occurring at a rate of about 2 to 3 per year worldwide. A primary consequence of the failure of a tailings impoundment is the flow of liquefied tailings. Such flows have been responsible for considerable loss of life, environmental damages and economic costs and represent one of the major risks associated with mining. Tailings, specifically those from hard rock mines, are particularly susceptible to liquefaction (a significant loss of shear strength) that can cause failure of the retention dyke and the release of liquefied tailings. Tailings liquefaction can be induced in dynamic loads, such as earthquakes, or static loads, such as dyke raising, erosion (loss of confining stress) or foundation movement. Aubertin et al. (2002b) considered placing waste rock in tailings impoundments in tandem with tailings deposition to improve the environmental and geotechnical performance of the impoundments. The waste rock would be placed to create relatively narrow, continuous inclusions along planned routes in the impoundment. It was postulated that these waste rock inclusions would provide a number of benefits, particularly by accelerating the consolidation of the tailings and acting to reinforce the impoundment with respect to static and seismic loads.