Tailings Disposal - Mining and the Environment: From Ore to Metal - page 728

tailings are thickened to high-density slurry or paste consistency using a high rate or deep
thickener or similar equipment. Conventional centrifuge pumps can pump thickened tail-
ings. Paste tailings require positive displacement pumps for their transfer. Tailings paste
plants are usually located close to the tailings discharge point.
Dry stacking of tailings, a technique pioneered by Alcoa, requires that the tailings are
de-watered to a 'cake' using vacuum belt i lters, drum i lters or similar ( Figure 18.7 ). The
cake is not pumpable and must be transferred to the disposal site by trucks or conveyor
systems. Dewatered tailings can be disposed of in engineered piles on prepared ground.
Embankments may be constructed around the perimeter of the site to collect runoff
and seepage from the pile, thus preventing it from escaping into the environment. With
cemented tailings, the thickened tailings are mixed with cement to generate a product that
is resistant to erosion and liquefaction under seismic loading.
Along the continuum of slurry, thickened, paste, dry tailings and i nally cemented tail-
ings, the solids contents and costs of production increase. However, the requirement for
large embankments reduces and the resistance to erosion and liquefaction under seismic
loading increases.

FIGURE 18.8
Typical Tailings Storage Layouts

Topographic conditions usually dictate the
confi guration of above grade tailings storages.
As with waste rock storages, additional storage
capacity can be obtained by taking advantage of
natural depressions in the landscape.

Single Ring Dike (Turkey's Nest)
Impoundment

Segmented Ring Dike (Multiple Cell)
Impoundments

Single Hill-Side
Impoundment

Multiple Hill-Side
Impoundments

Single Cross-Valley
Impoundment

Multiple Cross-Valley
Impoundments