URANIUM MINING METHODS

Based on the current understanding of uranium deposits in the Commonwealth of Virginia, extraction of uranium ore would use open-pit mining, or underground mining, or a combination of both (Figure 4.1). These general terms incorporate a large variety of design possibilities—there are as many methods of mining uranium as there are orebody sizes, shapes, and mineral constituents. The orebody size, location, orientation, rock quality, and the distribution of the valued minerals in it—along with site location and infrastructure—all play a part in the selection of the mining method and the overall plan for developing an orebody. Mines may range in size from very small underground operations, with considerably less than 100 tons of production per day, to large open-pits that move hundreds of thousands of tons of ore and waste per day. The descriptions of uranium occurrences in Virginia contained in the previous chapter indicate that most potential deposits will likely be hosted in a hard-rock setting, although geopolitical and market factors may in time enable uranium production as a byproduct of heavy mineral sand mining.

Underground Mining

Site-specific conditions, such as the depth of the ore deposit, its shape, surrounding geological conditions, and other factors, could result in the selection of an underground mining technique. In that case, the primary opening into an underground mine to provide access for people, materials, and equipment and to enable the ore to be brought to surface can be a shaft sunk vertically or on an “incline”; a “decline,” which is a ramp driven into the earth usually in a spiral fashion; or an “adit,” which is a horizontal opening driven into the side of a hill or mountain (Figure 4.1).

Both vertical and inclined shafts must be equipped with hoists and head-frames, which are the structures at the top of the shafts that enclose and operate the hoists used for transporting ore and mine personnel (Figure 4.2). Ramps usually spiral downward so that rubber-tired mobile equipment will have access to the mine. In some cases, ramps are driven in a straight line to accommodate conveyor belts. Horizontal or level mine workings are referred to as “crosscuts” and “drifts”; vertical access workings are referred to as “raises” or ”winzes.”

Generally, orebodies are either vein type, massive, or tabular in shape, and both the shape and ore thickness influence the mining method used. Vein-type orebodies usually dip steeply, and this steepness can be used during mining with the ore being allowed to fall to lower levels to an extraction accessway (Figure 4.3). Uranium orebodies are often narrow and irregular. The strength of the ore material and the surrounding host rocks, as well as the ore grade and the distribution of the ore, influences the ore removal method. Mined openings may be either supported or self-supported. Some supported openings are held up



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