Application of sedimentology to the development and extraction of deep-mined coal

Abstract

Abstract Most deep-mined coal in the UK comes from the Westphalian A and B (Langsettian-Duckmantian) of the coalfields of the Pennine Basin, in which several sedimentary facies have been identified. Deep mining of coal may be divided into four main operations: shaft sinking and driving of access drifts; drivage of underground roadways; excavation of coal faces; and the provision of temporary underground storage. The prediction of the lithological, geometrical and geotechnical properties of the various sedimentary facies likely to be encountered during mining is important for the success of all these operations. Roadway location may be influenced by the geotechnical attributes of the sedimentary facies, which also govern the type of machinery and methods used to cut and support the roads. The thickness, quality and continuity of the coal, and the properties of the roof and floor, are important in selecting the location of longwall faces and in their productivity. Facies composed of strong sedimentary rocks are likely to be the most suitable for the location of staple shafts and bunkers for coal storage. The geotechnical properties of each of the sedimentary facies is described, with particular reference to their excavation and support characteristics, and the discontinuities of sedimentary origin that are likely to be present. Distal lacustrine delta facies appear to provide the optimum roof conditions for coal faces and roadways. A simple scheme for the prediction of the sedimentary facies which may influence mining is presented, and a variety of mapping techniques, including facies maps, isopach maps and palaeocurrent analysis, are outlined. An improved knowledge of the properties and distribution of the various sedimentary facies at a mine site should lead to improved productivity and a reduction in risks and costs.