Performance of frozen tailings dams

A tailings pond had to be constructed in a cold permafrost area in poor geotechnical conditions as related to southern areas. The dam foundations consist of pervious frozen sands and fractured rock which would be difficult to seal if they became unfrozen. The only fill construction materials available were pervious sands. The tailings dams were designed on the basis that they would freeze and would maintain the foundation sands and fractured rock frozen even when water was raised against the upstream face. The dams and foundations had to remain frozen to prevent seepage of untreated effluent and to maintain the stability of the dams. While the analysis showed that the frozen conditions would be maintained, there was a lack of published data of similar design. As a result, extensive temperature monitoring was pursued to confirm the extent of the thaw front in the dam and also to follow the freezing of an unfrozen zone located below a previous creek. This paper summarizes the design and construction of these dams and presents the results of four years of temperature monitoring which confirmed the design basis.