This revised edition presents an engineering design approach to ventilation and air conditioning as part of the comprehensive environmental control of the mine atmosphere. It provides an in-depth look, for practitioners who design and operate mines, into the health and safety aspects of environmental conditions in the underground workplace.
In the vacuum of outer space, human astronauts rely on the artificial atmosphere of a spacecraft for their life support system. While differing in locale and mission, human miners are no less dependent on an artificial atmosphere to sustain them in underground mines where the air may be stagnant and contaminated.
It is evident that both miners and astronauts confront a hostile environment, and that both groups must depend on a ventilationâair conditioning system to supply them adequate air for breathing.
Under even normal circumstances, excavation in the earthâlike exploration in spaceâcan be fraught with a variety of environmental problems and hazards. While ground support is an obvious and compelling need, the most vital aspect of the mine environment to control is the atmosphere of the workplace.
To the mining engineer, ventilation is the most versatile atmospheric control tool. It is the process relied on to accomplish most environmental control underground. Mine ventilation is essentially the application of the principles of fluid dynamics to the flow of air in mine openings. As the primary means of quantity control, ventilation is responsible for the circulation of air, in both amount and direction, throughout the mine. It is one of the constituent processes of total mine air conditioning, the simultaneous control within prescribed limits of the quality, quantity, and temperature-humidity of mine air (Anon., 1993).
Increasingly, in underground mining, environmental objectives require that we condition air to meet quality and temperatureâhumidity standards as well as quantity criteria. In recent years, these standards have been raised substantially. Although threshold limits are based on human safety and tolerance, increasing concern is being expressed for standards of human comfort as well. The provision of a comfortable work environment is both cost-effective and humanitarian. Worker productivity and job satisfaction correlate closely with environmental quality. Further, excessive accident rates and workersâ compensation rates are a consequence of unsatisfactory as well as unsafe environmental conditions. No mining company today can afford to be lax in its environmental and air-control practices.
Historical Perspectives and Natural Constraints
The importance of mine ventilation and air conditioning has not just newly been recognized. From the onset of underground mining in Paleolithic times, perhaps as early as 40,000 BCE (B.C.) (Gregory, 1980, p. 50), miners confronted oxygen deficiency, toxic gases, harmful dusts, and debilitating heat. As miners became more skilled, by the first millennium BCE, they learned to course the air through multiple openings or circuits to provide fresh air to the working face (Lacy and Lacy, 1992, p. 5) and to use fire-induced air currents (McPherson, 1993, p. 2).
By the Middle Ages, mine ventilation enjoyed the status of a mining art. In the most celebrated early mining treatise, Georgius Agricola (1556, p. 200), a respected German scholar and scientist, decried the evils of the foul atmospheric environments in which miners had to work and pictured their still-primitive efforts to combat these conditions:
I will now speak of ventilating machines. If a shaft is very deep and no tunnel reaches to it, or no drift from another shaft connects with it, or when a tunnel is of great length and no shaft reaches to it, then the air does not replenish itself. In such a case it weighs heavily on the miners, causing them to breathe with difficulty, and sometimes they are even suffocated, and burning lamps are also extinguished. There is, therefore, a necessity for machines which the Greeks call
and the Latins, spiritalesâalthough they do not give forth any soundâwhich enable the miners to breathe easily and carry on their work.*
Figures 1.1a-c, taken from Agricolaâs book, portray some of these early âventilating machines.â A contemporary history of mine ventilation is presented by McPherson (1993, pp. 1-7).
[Parts (a)-(c) from Agricola, 1556. By permission from Dover Publications, Inc., copyright 1950.]
Technology has vastly improved mine ventilation, although environmental challenges underground still abound. Depth, the most serious natural constraint, sets the ultimate limit, specifically through rock pressure and rock temperature. Not only do rock pressures rise inexorably with depth but temperatures do also, with subsequent deterioration of the atmosphere. According to Spalding (1949, p. 238):
Of all the factors which affect mining operations, high rock temperature is the one most often likely to limit the depth to which those operations can be extended. The science of ventilation is therefore rapidly becoming the most important branch of deep mining.
At great depths, ventilation requirements and costs eventually climb to unsustainable levels. To preserve mine atmospheric quality under these intense heat conditions, ventilation at great depths must be supplemented by air conditioning.
Although heat generated by depth imposes the ultimate limit, the mine and its atmosphere have other detrimental conditions to withstand. These consist usually of airborne contaminants such as gases and dusts. As mines expand in size, complexity, manpower, and mechanization, demands on the ventilationâair conditioning system to maintain more stringent standards of environmental quality likewise rise. Fortunately, advances in mining science and technology tend to keep pace with worsening hazards underground. The struggle, however, is a continuous one reflected in both human safety and operating costs.
1.2 CONTROL PROCESSES
Lest confusion arise in the mind of the reader, it is well to clarify some of the terms related to environmental control of the mine atmosphere. Used alone, in mining parlance, air conditioning denotes only the function of temperatureâhumidity control, generally cooling or heating. To signify total mine air conditioning and all the functions of environmental control i...
