Standard structures of the country rocks around the coal in existing and deep horizons of the Prokop'evsk-Kiselevsk coalfield of the Kuzbass

Abstract

Mining operations in the lower existing horizons in the Prokop'evsk-Kiselevsk coals in the Kuzbass is greatly complicated by rock pressure, which increases with depth. To investigate the conditions under which rock pressure develops and to predict its effect on the efficiency and safety of the mining systems used we need to know the properties and structural characteristics of the whole of the country rocks within a specific sector of the mine or take.This communication gives the results of investigations into the structural characteristics and properties of the country rocks enclosing the principal coal seams of this coalfield: the IV Vnutrennyi, Gorelyi, and Moshchnyi. About 40% of the reserves of the coalfield are contained in these seams. They have maximum thickness and are generally accorded priority in working; this usually predetermines the sequence and intensity of mining of the whole series or group of seams in the series. The wall rocks of these seams consist largely of thick beds of strong arenaceous rocks, the overall thickness of which is 45-80 m. Exposure may lead to sag over extensive areas, creating dangerous abutment pressure concentrations at the marginal zones of the coal seams being woEked.To predict manifestations of rock pressure, primarily abutment pressure, we need to know the overall thickness of the roof and floor rocks, which actively interact with the marginal sectors of the solid coal and have been termed [I, 2] the "active roof" and the "active floor." These conuepts are somewhat arbitrary because the overall thickness of the roof and floor rocks which exert an influence on the operating conditions of the sys=em "roof--coal seam--floor" depends on n,~,~rous factors: geological, technical and engineering.From investigations of cross sections of mine workings and 120 prospecting boreholes (up to 1200 m deep) and on the basis of a comparative assessment of the results of field measurements of displacements of underworked and overworked rock masses, for the principal seams of the Prokop'evsk-Kiselevsk coalfield we propose to take the active roof thickness as 50 m (which corresponds approximately'to a sixfold-eightfold thickness of the coal seam or layer), and the active floor thickness as 20 m.These assumptions enabled us to compare the quantitative ratio of the lithological composition and variability of structure of the active roof and floor of the principal coal seams in the Prokop'evsk region. St was established that the rocks of the active roof and active floor are mainly sandstones and siltstones (75-90%). The amount of argillites in the active roof varies from 7 to 15%, and in the active floor from I0 to 25%. This pattern is traced throughout virtually all the mining fields of the region; on this basis we can infer that the wall rocks of the principal thick se-m-exhibit relatively the same quantitative ratio of the lithologic varieties and are predominantly strong and not readily caved.The structural characteristics of the rocks of the active roof and active floor are primarily du...