Ascending development

ASCENDING DEVELOPMENT (EN: method of ascending exploitation mining; DE: schwebender Abbau; FR: exploitation en montant, exploitation ascendante; ES: explotacion ascendente; RU: восходящая разработка) is the procedure for the conducting of the underground mining works, in case of which there is processed primarily the lowest seam of the stratigraphic suite, the layer of the seam, or the level (tier), later the above-lying seam, and so on.

They use the ascending development of the seams in the exceptional cases, when the underworking permits to eliminate the danger of the sudden outbursts of the coal and gas, of the mine bumps, to perform the degassing, the draining of the seams, the decreasing of the strength of the coals, and also when there emerges the necessity for the priority processing of the seams with the coal of the high quality, independently of their position within the stratigraphic suite. In case of the ascending development of the seams, there are the determining parameters the minimal thickness of the rocks between the seams, in case of which there is acceptable the underworking of the overlying seam, and the thickness of the seam, which is processed. The minimal thickness of the rocks between the seams, in case of which there is allowed the ascending development of the seams, with the underworking of them using the thin layers and the layers with the average thickness, which are being developed using the collapse of the roof, must amount to at least 6 times the thickness of the seam, within which the underworking is performed. In case of the usage of the stowing, or in case of the filling of the goaf space within the underworked seam with the waste rock, which is bypassed from the upper horizon, the minimal thickness of the rocks between the seams must be at least 3 times the thickness of the seam, within which the underworking is performed. In case of the seams, which are being developed together, the value of the outpacing of one stope by another stope depends on the character of the tectonic faults and movement of the rocks between the seams, mainly within the so-called leading layer. There is often leading the layer of the rocks within the major roof of the seam. The minimal outpacing within the space must be at least 60-100 metres, and within the time 1.5-2 months.

They use the ascending development of the layers in case of the impossibility of the processing of the thick seam using the single layer without the stowing, with which it is possible to work from the top down (the hydraulic stowing, and so on); the ascending development is possible only in case of the control of the rock pressure within the layers using the complete stowing of the goaf space. Because the stowing massif is prone to the shrinkage, for the prevention of the cracking of the above-lying massif of the coal, and for the prevention of the possible complications during the excavation of this massif, the stowing material must have the coefficient of the shrinkage of at most 8-10%, and in the individual cases, there is expedient the usage of the binding additives, and the chemical strengthening of the country rocks and coal within the weakened (disturbed) stopes (the polymeric anchors, and so on). Within the USSR, they use the ascending development of the layers mainly within the steep seams.

The ascending development of the levels (tiers) is allowed at the underground mines of up to the Category II inclusive because of the methane, with the aim of the acceleration of the commissioning of the first clearing stopes, or with the aim of the draining of the heavily water-flooded seams and layers of the rocks. The limitation is caused by one-sided or two-sided underworking of the transport drifts of the second and subsequent levels (tiers), which worsens the conditions for their maintenance, and is also caused by the additional inflow of the methane from the goaf space into the air-supplying drifts. They usually do not use the ascending development of the levels (tiers) within the inclined part of the mine field.