Underground excavations in rock / Подземная разработка в горных породах

For many cencuries miners have been excavating below the ground surface in their ceaseless search for minerals. Originally, these underground operations were simply a downward extension of the small excavations created to exploit surface outcrops. As mineral exploration methods became more sophisticated, resulting in the discovery of large ore bodies at considerable depth below surface, underground mining methods were developed to exploit these deposits. These new mining methods were evolved from hard won practical experience and one must admire the skill and courage of the mining pioneers whose only acknowledgement of the difficulties which they encountered was to admit that there were certain areas of "bad ground" in the normally "good ground" which they worked.
Most underground mining excavations were, and indeed still are, of a temporary nature. Provided that safe access can be maintained for long enough for the ore in the vicinity of the excavation to be extracted and provided that the subsequent behaviour of the excavation does not jeopardise operations elsewhere in the mine, an underground mining excavation ceases to be an asset after a relatively short space of time. Clearly, the resources allocated to investigating the stability of such an excavation and the quality and quantity of support provided must be related to the length of time for which it Is required to maintain stabil-i ty.
The increasing size of underground mining operations during the past few decades has led to the introduction of a concept which would have been foreign to underground miners of earlier times - the concept of permanent underground excavations. Major shaft systems with their surrounding complex of haulages, ore passes, pump chambers and underground crusher stations are required to remain operational for several tens of years and , from the miner's point of view, are permanent excavations. in addition to being large in size, some of these excavations can house expensive equipment and can be manned on a regular basis; consequently such excavations must be secure against rockfalls and other forms of instab i1i ty. <...>