9 UNDERGROUND MINE DEVELOPMENT

9.5 SHAFT HOISTING SYSTEMS

The hoist, together with its associated plant for an underground mine, is the single most important and expensive element of the mine plant (Butler and Schneyderberg, 1982). Because it is also the most sophisticated part of the entire plant, it is not feasible to build in redundancy (except for the prime mover), yet it must perform with close to 100% reliability. Its cost may be on the order of 5 to 10% of the entire development budget. Obviously, wise engineering judgments are called for in the design of the hoist plant.

FIGURE 9.17. Basic roof-bolting methods: mechanical point-anchor bolt (left), resin-anchor bolt (right), basic coal mine bolting plan (center). (After Lucas and Adler, 1973. By permission from the Society for Mining, Metallurgy, and Exploration, Inc., Littleton, CO.)

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FIGURE 9.18. Underground roof control systems: (a) roof bolt truss, (b) timber set, (c) stee1 set, (d) yieldable arch, (e) temporary hydraulic jacks, (f) wood crib. Figure 9.18(f) from Barczak and Gearhart (1994). Others from Lucas and Adler, 1973 (by permission from the Society for Mining, Metallurgy, and Exploration, Inc., Littleton, CO.)

9.5.1 Components of Hoist Plant

The hoist plant consists of all those components of the mine plant that are necessary to elevate ore, coal, stone, or waste and to raise and lower personnel and materiel in the mine. It is made up of some of the constituents of the mine plant that were discussed in Section 9.3. Classified by location, they consist of the following:

1. Surface plant

a. Hoist room (headframe- or ground-mounted)

(1) Hoist drum or sheave (imparts motion to rope)

(2) Hoise electrical and mechanical equipment (prime mover, brake. clutch, controls)

(3) Hoist ropes (steel wire strands, woven in a pattern or lay)

b. Headframe (tower or A-frame, steel or reinforced concrete)

(1) Idler sheaves

(2) Storage bins (ore and waste)

(3) Skip dump mechanism (overturning or bottom dump)

2. Shaft plant

a. Skips (bulk transport)

b. Cages, elevators (personnel, materiel)

c. Shaft guides (tracks for skips and cages)

3. Underground plant

a. Dump and storage bin

b. Crusher (if size reduction required for hoisting)

c. Loading pocket

d. Personnel and materials-handling facilities

Figure 9.19 assists us in visualizing these components of the hoist plant, assuring a vertical shaft as the main access opening. With little modification, the same layout would also suffice for an inclined shaft using hoisting (a slope, ramp. or drift mine differs, presumably because hoisting would not be used).

FIGURE 9.19. Components of the hoist plant installed with a vertical shaft. (After Lucas and Haycocks, 1973. By permission from the Society for Mining, Metallurgy, and Exploration, Inc., Littleton, CO.)

9.5.2 Hoisting System

It is with the hoisting s3stenl itself those components of the hoist plant located in the hoist room that engineering design is mainly needed. Three key factors govern hoist selection:

1. Production rate, or tonnage to be hoisted per unit of time

2. Depth of shaft

3. Number of levels to be accessed

There are only two hoist types commonly used today: drum and friction. A drum hoist stores the rope not extended in the shaft on the face of the drum. A friction hoist passes the rope (or ropes) over the top of the drive wheel but does not store it. Figure 9.20 shows a general diagram of both types. In addition, special drum hoist design for deeper shafts is occasionally required. The

FIGURE 9.20. Diagrams of mine hoists. (Top) Double-clutched, double-drum hoist. (Bottom) Multirope friction-sheave hoist. (After Russell, 1982. By permission from the Society for Mining, Metallurgy, and Exploration, Inc., Littleton, CO.)

multidrum Blair hoist was devised for deep mines in South Africa. The configurations for two Blair hoists are shown in Figures 9.21d and 9.21e. While there is no hard set of rules for selecting a type of hoist, Harmon (1973) and Russell (1982) have provided general applications (Table 9.2). In addition, Culp (2002) provides general guidelines. He makes note that technical criteria are often overshadowed by regional biases. This leads one country to prefer a friction hoist for the same application where another would choose a drum hoist. Here is Culps summary of common hoist configurations and their most common applications.

9.5.2.1Single-Drum, Unbalanced Hoist

A single-drum hoist is the simplest type, with one rope and one conveyance (Fig. 9.21a). Because there is no balancing load, it requires a very high ratio of power to capacity. It is the most flexible configuration because there is no consideration required for the position of a balancing conveyance. The most common applications are shaft-sinking hoists, auxiliary hoists (for escape and other low-utilization applications), and shallow service hoists.

9.5.2.2Single-Drum, Counterweighted Hoist

When configured with two ropes, winding in opposite directions so that one conveyance ascends while the other descends, the conveyances balance each other and the power requirements decrease significantly (Fig. 9.21b). This configuration is also known as an 'over/under' hoist. The balanced loads decrease

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