A review of dry cover placement on extremely weak, compressible tailings

This paper reviews key issues related to the placement of dry (soil) covers on extremely weak, compressible fine tailings. The design and construction of soil covers on such tailings often presents a formidable challenge to t he geotechnical as well as the environmental engineer due to the low shear strength, poor trafficability, and high settlement of underconsolidated tai lings at the time of reclamation. The geotechnical issues to be considered include. (I) consolidation of near-surface tailings to achieve strength gai ns, improve trafficability, and allow safe placement of initial cover layer ; (2) stability of tailings slopes during dewatering of tailings ponds and/ or cover placement and (3) long-term settlement of tailings and its impact on cover integrity and final surface shaping. The environmental issues to b e considered include. (I) management of contaminated (free) pond water; (2) management of contaminated pore water expelled during tailings consolidati on; and (3) management of (uncontaminated) surface water on top of the cove r. This paper summarizes recent experiences gained in a large uranium taili ngs reclamation project. it is concluded that a careful consideration of bo th geotechnical and environmental issues during the planning stages greatly reduces the costs and environmental risks associated with fine tailings re clamation.