技术报告-尾矿库设计及评估 (英文)(27)

技术报告-尾矿库设计及评估 (英文)

Design and Evaluation of Tailings Dams

Site independence benefits the design, since less effort and cost are needed to counteract topographic

obstacles, soil conditions, climatic conditions, and construction obstacles. The uniform layout, shape, and

flat terrain prevents surface runoff from entering the impoundment and decreases the requirements for flood

control measures.

3.TAILINGS IMPOUNDMENT DESIGN

The actual design of a tailings dam and impoundment occurs only after the site has been selected. However,

the site selection and design are best considered to be a dynamic process. A number of design principles

should affect the site selection process as well as the determination of the embankment type and the

impoundment configuration. This section first describes some of these fundamental design principles as well

as major design variables and site-specific factors that influence ultimate design. As noted previously, the

major considerations in the design of a tailings dam and impoundment are stability, cost, and environmental

performance.

3.1Basic Design Concepts

In general, tailings impoundments (and the embankments that confine them) are designed using information

on tailings characteristics, available construction materials, site specific factors (such as topography, geology,

hydrology and seismicity) and costs, with dynamic interplay between these factors influencing the location (or

siting) and actual design of the impoundment. Because water is a major component in any tailings

impoundment system, principles of hydrology (applied to flow of water through and around the tailings

embankment) dictate many of the rules of tailings impoundment design. Indeed, because impoundment and

dam stability are in large part a function of the water level, these principles are of fundamental concern in the

design of any tailings impoundment.

One of the basic principles used in the design of impoundments and their embankments is the maintenance of

the phreatic surface within the embankment. The phreatic surface is the level of saturation in the

impoundment and embankment (the surface along which pressure in the fluid equals atmospheric pressure

(CANMET 1977)); in natural systems it is often called the water table. The phreatic surface exerts a large

degree of control over the stability of the embankment, under both static and seismic loading conditions (Vick

1990). The major design precept is that the phreatic surface should not emerge from the embankment and

should be as low as possible near the embankment face (Vick 1990). This basically maintains a pore

pressure at the face of the embankment lower than atmospheric pressure plus the weight of the embankment

particles and maintains the face of the dam. Thus any factors that might affect the phreatic surface in the

embankment may also affect stability of the embankment. The primary method of maintaining a low phreatic

surface near the embankment face is to increase the relative permeability (or hydraulic conductivity, since

water is the fluid) of the embankment in the direction of flow. (See Figure 7.)

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