Every operation connected with the working of a deep-level mine has, to a greater or lesser extent, a direct bearing on the costs of production, and hence, profitability of the mine. If adequate mine planning is not done in the early stages in the life of a mine, considerable expenditure can result from the cost of maintaining mine service tunnels, production delays in stopes caused by poor strata control, distortion of fittings in hoisting shafts, rockbursts and so on. In fact, the optimum profitability of a deep-level, hard-rock mine can only be achieved if the layout of the shaft systems, ore passes, tunnels, stoping areas and other underground excavations are designed to withstand or accommodate the rock stress conditions that will be created by mining operations. In South Africa where the deepest mines in the world are located, access to the underground workings of most deep-level gold mines is via vertical shaft systems and a network of tunnels connecting the shaft systems to the stoping areas. In current practice, there are two basic methods of extracting the gold-bearing reef,*namely the scattered stoping method and the longwall stoping method. The choice of the stoping method is governed largely by the anticipated gold distribution and payability of the reef in the area, the geological conditions, the degree and complexity of faulting and dyke intrusions, the depth at which the gold-bearing reef is to be mined and the inclination rind width of the reef. The longwall system was first introduced at the East Rand Proprietary Mines Limited in 1942 (1) in an effort to combat the rockburst hazard which appeared to increase with increase in depth. This mining method became standard practice on that mine for stoping operations 700 ft. below the surface. Since that date, several deep mines on the Central Rand, East Rand and West Wits gold mining areas have adopted this method. A typical longwall stoping configuration at a very deep mine is shown in Fig. 1. The scattered mining method, which is practiced widely in the Orange Free State, Klerksdorp and Evander gold fields, takes its name from the irregular extraction of the reef which lies between geological intrusions and/or dislocations of the reef. A typical mining area in the Orange Free State gold fields is shown in Fig. 2 where because of severe faulting, numerous small areas of reef have been mined as discreet blocks between the faults to create the "scattered mining" pattern. It is claimed that longwall mining provides the following advantages over the scattered stoping method practiced in most of the geologically faulted deep mining areas (2):
There is a large reduction in the number of remnants created.
Pronounced lags or leads between faces, which are known to be closely associated with rockbursts and strata control problems, are obviated.
The shape of a longwall stope enables better utilization of ventilating air.
Concentrated mining is achieved, which provides improved supervision, services, etc.
Reef development is reduced considerably and the loss of production associated with moving personnel to new areas is minimized.