技术报告-尾矿库设计及评估 (英文)

Design and Evaluation of Tailings Dams

DESIGN AND EVALUATION OF TAILINGS DAMS

1.INTRODUCTION

In order to obtain the metals and other minerals needed for industrial processes, fertilizers, homes, cars, and

other consumer products, large quantities of rock are mined, crushed, pulverized, and processed to recover

metal and other mineral values. A fine grind is often necessary to release metals and minerals, so the mining

industry produces enormous quantities of fine rock particles, in sizes ranging from sand-sized down to as low

as a few microns. These fine-grained wastes are known as "tailings."

Until recent decades, the majority of mines were small underground operations with correspondingly modest

requirements for tailings disposal. Since that time, due to increasing demand, it has become economical to

mine large lower-grade deposits by utilizing advances made by mining equipment manufacturers and

developments in mining and milling technology. This has greatly increased the amount of tailings and other

wastes generated by individual mining projects and by the mining industry as a whole.

There are approximately 1,000 active metal mines in the United States (Randol, 1993) Many of these have at

least one tailings impoundment and often several impoundments grouped together in cells. EPA estimates

that there may be several thousand tailings impoundments associated with active non-coal mining, and tens of

thousands of inactive or abandoned impoundments.

By far the larger proportion of ore mined in most industry sectors ultimately becomes tailings that must be

disposed of. In the gold industry, for example, only a few hundredths of an ounce of gold may be produced

for every ton of dry tailings generated. Similarly, the copper industry and others typically mine relatively

low-grade ores that contain less than a few percent of metal values; the residue becomes tailings. Thus,

tailings disposal is a significant part of the overall mining and milling operation at most hardrock mining

projects. There are several methods used for tailings disposal. These include disposal of dry or thickened

tailings in impoundments or free-standing piles, backfilling underground mine workings and open-pits,

subaqueous disposal, and the most common method, the disposal of tailings slurry in impoundments.

Modern tailings impoundments are engineered structures for permanently disposing of the fine-grained waste

from mining and milling operations. At some projects, tailings embankments reach several hundred feet in

height and the impoundments cover several square miles.

Historically, tailings were disposed of where convenient and most cost-effective, often in flowing water or

directly into drainages. As local concerns arose about sedimentation in downstream watercourses, water use,

and other issues, mining operations began impounding tailings behind earthen dams, which were often

constructed of tailings and other waste materials. The impoundments served the dual purpose of containing

the tailings and, particularly in the arid west, allowing the re-use of scarce water.