Managing tailings consolidation

Tailings dams designed and constructed for use in the gold mining industry over the past decade or two are different from tailings dams constructed previously because the grain size distribution of the tailings being deposited has become very fine. The grain size distribution of mill tailings 20 years ago was about 70 percent finer than a 200 mesh screen size; now it is typically between 90 and 95 percent finer than the 200 mesh. With this finer grind, the deposited material is much slower to settle, drain, and consolidate. This paper analyzes the settling mechanisms of these fine tailings under normally drained areal and subareal deposition conditions. The use of wick drains to speed tailings drainage and consolidation is evaluated and compared with normal (gravity) drainage. The conclusions reached in this paper are extended to their impacts on the practical design and closure aspects of tailings impoundments.