the creation of normal atmospheric conditions in a quarry. Quarry ventilation has acquired great importance predominantly because of the increase in quarry depth to several hundred meters and the large scale of the mining operations, which result in significant dust accumulation and atmospheric pollution. A distinction is made between natural and artificial ventilation of quarries. Natural ventilation is achieved by means of the wind, if wind speed is greater than 2 m/sec, or thermally, if wind speed is less. Wind speed is thus seen to determine whether the wind or thermal system is used.
In wind systems, a free air stream is created in the quarry (Figure 1). Within this stream, the air speed varies from the wind speed at the stream’s upper limit to zero at the stream’s lower limit, the air then moving in the opposite direction (recirculation). The expansion angle of the stream α ≈ 15°. In the recirculation system, pollutants are removed by the air moving above the line OB. If the angle of incline of the ventilated side of the quarry β ≤ α, the zone of countercurrents AOC disappears and the ventilation system becomes a direct-flow system, in which all the air moving in the quarry removes the pollutants.
Thermal ventilation involves a convective system, in which air heated on the surface of the quarry forms rising currents, and an inversion system, in which cooled air descends into the quarry.
Natural ventilation of a quarry can ensure normal clean atmosphere at depths up to 200 m. At greater depths artificial ventilation is required, which uses devices with propeller and turbojet aircraft engines and thermal devices that create convective air currents by burning fuel.
In planning for quarry ventilation it is necessary to correctly orient the contours of the quarry relative to the prevailing winds, to choose the operational technology that least pollutes the atmosphere, to evaluate the effectiveness of natural ventilation, and to select the means, systems, and periods for artificial ventilation.
REFERENCES
Bitkolov, N. Z., and V. S. Nikitin. Provetrivaniekar’erov. Moscow, 1963.Filatov, S. S., V. A. Mikhailov, and A. A. Vershinin. Bor’ba s pyl’iu i galantina kar’erakh. Moscow, 1973.
Ushakov, K. Z., and V. A. Mikhailov. Aerologiia kar’erov. Moscow, 1975.
K. Z. USHAKOV
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