技术报告-尾矿库设计及评估 (英文)

Design and Evaluation of Tailings Dams

There are, however, a number of disadvantages to tailings impoundments requiring attention in design,

including (Environment Canada 1987):

Difficulty in achieving good flow distribution

Difficulty in segregating drainage from uncontaminated areas

Difficulty in reclamation, particularly with acid-generating tailings, because of the large surface

area and materials characteristics

Inconsistent treatment performance due to seasonal variations in bio-oxidation efficiency

Costly and difficult collection and treatment of seepage through impoundment structures

Potentially serious wind dispersion of fine materials unless the surface is stabilized by

revegetation, chemical binders, or rock cover.

2.1Methods for Tailings Disposal

Because mine tailings produced by the mill are usually in slurry form, disposal of slurry tailings in

impoundments made of local materials is the most common and economical method of disposal. There are

four main types of slurry impoundment layouts; valley impoundments, ring dikes, in-pit impoundments, and

specially-dug pits (Ritcey 1989). These impoundment configurations are explained in more detail below,

with major emphasis on valley impoundments, as they are the most common. Before describing

impoundments, several other methods of tailings disposed are briefly described below.

In some cases, tailings are dewatered (thickened to 60 percent pulp density or more) or dried (to a moisture

content of 25 percent or below) prior to disposal. The efficiency and applicability of using thickened or dry

tailings depends on the ore grind and concentrations of gypsum and clay as well as the availability of

alternative methods. Except under special circumstances, these methods may be prohibitively expensive due

to additional equipment and energy costs. However, the advantages include minimizing seepage volumes and

land needed for an impoundment, and simultaneous tailings deposition and reclamation. (Vick 1990)

Slurry tailings are sometimes disposed in underground mines as backfill to provide ground or wall support.

This decreases the above-ground surface disturbance and can stabilize mined-out areas. For stability reasons,

underground backfilling requires tailings that have a high permeability, low compressibility, and the ability to

rapidly dewater (i.e., a large sand fraction). As a result, only the sand fraction of whole tailings is generally

used as backfill. Whole tailings may be cycloned to separate out the coarse sand fraction for backfilling,

leaving only the slimes to be disposed in an impoundment. To increase structural competence, cement may

be added to the sand fraction before backfilling (Environment Canada 1987).

Open-pit backfilling is also practiced, where tailings are deposited into abandoned pits or portions of active

pits. The Pinto Valley tailings reprocessing operation, located in Arizona, uses this method to dispose of