Strata mechanics in coal mining / Механика пластов при добыче угля

Development of "oal mining throughout the world has increased in the last decade due to the need for energy, and this trend will continue, at least, until the end of this century. Increased production requires enlarging underground mine structures and rapid coal extraction, in which coal mine strata mechanics play an essential role. Coal mine strata mechanics first interested me in the late 1940's during practical work as a student and later as a graduate mining engineer in St. Barbara Coal Mine, Yugoslavia. I was fascinated in observing the mechanics of stress concentration and relaxation manifested by deformation and failure of coal pillars and roof falls in roadways, as well as effective strata control by almost illiterate miners as an integral part of mine operations. Miners were aware of particular acoustic emission effects before rooffalls during retreat long pillar mining; realizing that they could be indicated by a mouse's hearing system and its reaction by run. These warnings of roof falls were primitive, but effective, because accidents under these circumstances never occurred. This earlier practical knowledge was offundamental importance for later sophisticated research in strata mechanics and mine stability. Generally, in the last two decades the subject of rock mechanics in coal mining has been extensively investigated and discussed, as shown by the abundance of publications, where the authors more or less considered the strata and mining conditions of the region in which they live and work. This volume is no exception, because a large number of example are from the western coal fields of North America. At present there are several different philosophies of coal mine strata mechanics, arising from the different backgrounds of the specialists involved in this particular field, for example, highly theoretical concepts versus very practical concepts in solving problems. Also, the conceptual approach to coal mine strata mechanics by a mining engineer does not necessarily coincide with that of a civil engineer. Many underground civil engineering structures are integral and functional systems ofstatic rock masses in which the primary concerns are stresses induced by the size and shape of openings. The determination of such stresses requires a good engineering background and knowledge of the theory of mechanics. Mining engineering structures are temporary or semipermanent and are loosely integrated in the rock strata, and are dynamic rather than static. The mining stresses of primary interest are those with different play during coal extraction due to unca ved or caved roofs, stable or unstable pillars, and others, for whose determination ingenuity and mining experience is necessary in addition to theoretical knowledge.  <...>