Self-weight consolidation of mixtures of mine waste rock and tailings

Abstract

Mixtures of waste rock and tailings are compared with unmixed waste rock and tailings in a column study of self weight consolidation. Standard practice for surface mine waste disposal produces the two individual waste streams of waste rock and tailings. Waste rock dumps offer high strength and low compressibility characteristics but are prone to oxidation and metal leaching because of their high permeability and unsaturated conditions. Tailings deposits typically have low permeability and slow time rate consolidation properties but also have end land use issues and long term stability problems related to shear strength. Three mixtures of waste rock and tailings were loaded into columns and monitored for settlement, drainage, and pore-water pressure response for 100 days. A fourth column was built with waste rock only as a control. Mixtures with approximately 5:1 waste rock to tailings by dry mass were found to have a hydraulic conductivity similar to tailings alone and total settlements similar to waste rock alone. Mixture materials also remained saturated during the 100 day test. Results indicate that mixing waste rock and tailings for disposal is a promising idea that may help eliminate problems arising from current practices in mine waste disposal.Key words: co-disposal, hydraulic conductivity, self weight consolidation, tailings, waste rock.