68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference

A CASE STUDY: SEISMIC STABILITY OF AN UPSTREAM TAILINGS IMPOUNDMENT – EMPIRICAL METHODS AND INPUT GROUND MOTIONS

Session: Mining Geotechnique III / Géotechnique minière III

Miguel Medina, SNC Lavalin (Canada)
Denise Leahy, SNC Lavalin (Canada)
Nicolas Lemieux, SNC Lavalin (Canada)

This paper presents the implications of the selection and treatment of input ground motions for the seismic stability evaluation of an upstream-raised tailings impoundment currently under construction. This impoundment contains niobium tailings, considered susceptible to liquefaction under seismic loads. Therefore a shell of compacted coarse tailings was built along the perimeter and is subsequently raised in the upstream direction with a decreasing width with height. An extensive monitoring program of the compacted shell, including CPTu and SPT testing, has been implemented to evaluate the compaction methods implemented and for quality control. The site lies in the seismic zone that produced the 1988 Saguenay earthquake (magnitude 5.9) and is capable of producing earthquakes with magnitudes as great as 7.5. The different methodologies and results are compared and discussed in the light of the empirical liquefaction assessment method.