Study on Upper and Lower Gas Drainage and Prevention and Control Technologies in Deep High-Gas Mines
Authors: Pang Dongdong , Wang Xi , Yin Zhiqiang , Niu Xingang , Yang Peng , Ni Zongyu 
Published: December 2024

In response to the “three highs” problem in the mining of deep high-gas mines, the rapid increase in the coal seam permeability coefficient and gradual increase in coal and gas outburst problems have made gas control more difficult. This study considered the occurrence of remote outburst coal seams in the Zhujixi Mine as the research background and performed theoretical analysis, calculations, numerical simulations, and other technical methods to analyze the gas occurrence characteristics of the 11-2 coal seam and the feasibility of using this seam as a lower protective layer for mining. The pressure relief protection range for the overlying 13-1 coal seam, to the recovery of the 11-2 coal seam, was determined. A regional anti-outburst technology was proposed for underground through-layer and parallel-layer drilling, focusing on pre-gas extraction for the protective layer. In addition, a pre-gas extraction regional anti-outburst technology combining the surface and underground mining of the protected layer is also proposed. Gas occurrence in the 11-2 coal seam is uneven and has poor regularity, presenting high gas areas. It is significantly affected by the geological structures and shale properties of the coal seam roof and floor. The 11-2 coal seam is a stress-dominated and gas-outburst coal seam. The Zhujixi Mine presents a joint underground extraction and regional outburst prevention mode; that is, the 11-2 coal seam with a lower outburst risk is selected as the protective layer for mining first, whereas the 13-1 coal seam is protected while the gas in the protected layer is extracted. The 11-2 coal is characterized by the gas control mode of “one side, three lanes+ground drillings” to achieve multi-purpose, joint treatment, and continuous mining of one lane. The excavation face exhibits comprehensive anti-outburst measures, such as through-layer drilling pre-extraction and a coal mining face over the layer drilling pre-extraction area. During the mining period, surface drilling and a top extraction roadway are used to extract 13-1 coal-depressurized gas. By adopting joint extraction technology in the upper and lower mining areas, the residual gas content and pressure were measured at the underground excavation and mining working face. The predicted indicators did not exceed the standard levels, and no dynamic phenomena occurred. As a result of the application of the anti-outburst technology in the joint extraction area of the Zhujixi Mine, the proportion of extraction in the upper and lower mining areas was 56.7%, and the proportion of extraction in the underground mining area was 43.3%. These factors are interdependent and indispensable. The maximum height of the caving zone after mining the 11-2 coal face was 11.6 m, whereas the height of the fracture zone was 34.4-52.2 m. The 13-1 protective-layer working face is arranged on the upper part of the fracture zone or lower part of the curved subsidence zone, which can effectively increase the permeability of the 13-1 coal seam. Engineering practice has shown that the joint regional anti-outburst technology and engineering application in Zhujixi mine have achieved good results, forming a regional anti-outburst technology system for joint extraction of mines and providing a reference for the safety production of similar conditions in outburst mines.