Gate Road Development in High Gas Content Coal Seams at Karaganda Basin Coal Mines, Kazakhstan

Most coal seams, currently mined in the Karaganda Coal Basin, are prone to outburst. The main thick D6 coal seam is considered as most prone to outburst risk. Trials of advance degassing from the surface have not given positive results because of low permeability. 100mm diameter inseam holes are subsequently drilled in almost all longwall blocks to facilitate preliminary degassing of the coal seams. Gas extraction quantities are however low, even the holes are placed on suction To facilitate the gas release during longwall block development, of the main seam, a method of development below the seam was used. This gave rise to increase in permeability of overlying thick seam with high gas content, achieving a local degasification of the overlying seam by up to 90%. The initial development roadway was driven under the seam, in rock, at a distance of between 8-12 m from seam floor in the same contour of the future development roadway in the coal seam. A relief area was created as a result of stress redistribution above the roadway. Degassing holes were drilled from the rock development, into the seam area of the future coal seam development heading. During traditional in seam development, outburst preventive measures were taken, which increased the labour intensiveness of development working, sharply decreasing the development rate. Application of these new techniques allowed increased development rates in seams to be realised, from 25-40 m per month to 120-150 m in the outburst prone areas.