| In the history of coal mining, coal mine gas prevention and control has been an important issue to ensure safety in coal mines. Currently, gas drainage is one of the most important mine gas prevention and control measures. Gas drainage can not only reduce the amount of mine gas emission, reducing the likelihood of gas accidents, also contributes to the use of gas, saving energy while preventing greenhouse gas emitted directly into the atmosphere. In the process of coal seam group mining, the adjacent layers tend to be the main source of workface gas. In adjacent layers that gushing gas to working face, the upper adjacent layer gas emission is often greater than the lower adjacent layer. Therefore, study on overburden fracture evolution law when coal mining,gas enrichment law, gas drainage methods of an adjacent layer is helpful to solve adjacent strata large gas emission problems. This paper will be focused on the adjacent layer gas drainage 12# seam mining in Nanzhuang Mine in Yangquan. This paper analyzes the evolution of overlying strata fissures and gas occurrence theory.Combining mining conditions Nanchuang Mine 12# coal seam, through theoretical analysis, numerical simulation and similar experiment, overburden fracture distribution and gas high and low partitions enrichment laws are analyzed. This paper also proposed gas collaborative extraction programs and Nanchuang mine got a better application.Adjacent layer gas drainage system was built for Yangquan coal mining area 12#, which got promoted in the Dayangquan Mine.Yangquan Coal Mine Area is one of the country’s largest and most difficult gas drainage mine area. In this mine area, gas emission is very large and gas outburst occurs frequently, that the impact on coal mine production safety is very seriously. Yangquan Mine area consists a total of 15 mine coal-bearing layers; anthracite coal is the main type; 3#, 6#, 8#, 10#, 12#, 15# coal seam is the main mining seams; every seam is rich in gas. Sources of methane in mining faces statistical analysis showed that: the layer adjacent is the main source of face gas.According to the current theory foundation of the upper adjoining gas pressure relief drainage, the gas in the coal occurrence, coal porosity characteristics evaluation methods is summed up; the continuity equation in coal gas flow and diffusion- seepage equation is summarizes. This paper analyzes the theory of mining overburden caving zone, fractured zone and bend zone. An overview of critical layer theory and gasextraction and transport related "O" ring theory is summarized. According to these theories, this paper analyzes the Yangquan Coal Mine 12# coal seam fracture evolution distribution, calculated the 12# coal seam overburden "vertical three Bands" range of height and position of the key layer, and according to analysis results of fracture evolution law of the overburden, the gas emission sources and gas rich region are analyzed.According to the site geological conditions and criteria of similar experiments,similar experiments carried out to study the evolution of the overlying strata fissures of12# coal seam in Yangquan coal mine area. Using China University of Mining and Technology(Beijing) Mining Engineering Laboratory EWM-dimensional simulation test bench, the similar experiments were conducted. Through the analysis of experimental results, the overburden collapse morphology and distribution of the displacement field were obtained when the mining face was at a different location, and then the fissures development law of the overburden was analyzed. Based on the key layer subsidence curve analysis, the law of key layer broken during mining face sinking was studied.Using discrete element numerical calculation program UDEC4.00 for non-continuous media model, geological and mining conditions of Yangquan Nanzhuang 12# coal seam as the prototype, the process of overburden dynamic collapse while mining and dynamic evolution and distribution patterns of fracture field are studied, which provide a theoretical basis for the 12# coal seam adjacent layer of pressure relief gas drainage technology. The simulation results obtained the adjacent layer stress distribution changes with mining process; by post-processing simulation results changes of overburden displacement field were obtained; numerical simulation also obtained overburden mined crack field evolution model. Results of similar experiments and numerical simulation are consistent that they can confirm each other.The experimental results and the theoretical analysis and simulation results obtained "vertical three Bands" range and key layer position conclusions are close.According to the theoretical analysis, model test, numerical simulation results and field geological condition, results of fracture evolution law on the 12# coal seam in Yangquan overburden are obtained. FLUENT simulation carried out in accordance with the evolution of fractures, obtaining adjacent layer relieved gas enrichment zoning rules:in process 12# coal seam mining, the adjacent layers that have a larger contribution ofgas emission in faces is 8#, 9#, 10#, 11# coal seams and K4 limestone. bounded by 10#coal seam roof sandstone, located in the lower part of the sandstone, 10#, 11# coal seams and K4 limestone forms a low-gas-rich region. the low gas-rich region is in the transition zone caving zone and fracture zone with an extremely fractured development and a short distance from 12# coal seam. After mining of the 12# coal seam, pressure relief gas in this region will quickly relief and emits into mining space. 8# and 9# coal seam located near the top of the roof sandstone of 10# coal seam formed a high gas-rich region. This region is located in the transition zone of fractured area and the curve subsidence zone, where cracks are well developed, and the distance to 12# coal seam spacing is large, which is effected by mining later, after some distance as mining face go over, this region can unloads pressure and emits mining space.For the high and low enriched partition of adjacent layer mining relief gas of 12#coal seam in Yangquan mine area, the 12# coal seam in Yangquan mining area adjacent layer relief gas collaborative drainage technology is proposed. That is, according to the laws of relief time and space of each gas-rich region, using high and low drilling holes,drainage high gas-rich region and lower gas-rich zones. We first proposed gas collaborative drainage programs for Yangquan Nanzhuang 12# coal seam Face 4611,and numerical simulation approach is used to demonstrate the effect of extraction. The numerical simulation results showed that: gas collaborative drainage technology is suitable for gas prevention of Face 4611.Gas collaborative drainage technology first tested in Yangquan Nanzhuang Mine12 # coal seam Face 4611. The test results show that the gas collaborative drainage approach eliminates gas gauge problem in face mining period and accelerate the advance of the working face, leading to a substantial increase in the face yield. In the ensuing Nanzhuang 12# Coal Seam Face 4606 drainage test, the application of high,low drilling collaborative extraction technology made some improvements. Meanwhile,the mined-out area gas and the coal seam gas drainage are carried out, the comprehensive, three-dimensional drainage system of gas emission during face mining was formatted. Collaborative gas drainage technology system test results in Nanzhuang mine proved the validity of the adjacent layer collaborative drainage technology in 12#coal seam of Yangquan mining area. The application of gas collaborative drainage technology in the Dayangquan mine has been promoted and has achieved good economic, social and environmental benefits, showing the general applicability of gascollaborative drainage technology system.Collaborative drainage technology not only improves the safety conditions of workfaces in 12# seam, improves the working face yields, reduces carbon emissions,speeds up the face advance efficiency, and improves gas pumping rate, but also ensures the safety of efficient mining in 15# coal seam, improves resource utilization, extends the service life of the mine. Meanwhile South Coal mining group achieved good economic, social and environmental benefits by drainage gas utilization. Collaborative drainage technology in Yangquan mine area, other mines mainly mining 12#, 15# coal seam and setting 12# coal seam as the first mining and other mines with similar conditions of the coal seam group Mining has broad application prospects. The application of collaborative drainage technology improves the amount of face gas drainage and drainage rate, reduces carbon emissions, and uses the clean energy.The innovations of this paper are the following three points: 1) Through a comprehensive analysis of theoretical analysis, model test, numerical simulation and field tests, distribution of "vertical three zones" in Yangquan mine area 12# seam during the overburden is obtained, the position of key layer overlying strata is identified, and the overburden movement and deformation law, mining crack field evolution law, the law of the sinking of the key layer and stress variation on adjacent layers are obtained,the 12# coal seam adjacent layers crack field distribution and relief gas high and low partitions enrichment laws are obtained. 2) against the high and low enriched space and time partitioning features of relief gas in adjacent layer of 12# coal seam in Yangquan,we proposed collaborative drainage method that the high and low drills are respectively disposed to drainage adjacent high and low gas enrichment zone respectively. 3) Based on the field test results study, determine the relief gas drainage technology collaboration system that appropriates the adjacent layers of mining face of 12# coal seam in Yangquan due to mining pressure is determined, and a reasonable range the parameters such as the field of gas drainage drilling arrangement, gas drainage drilling hole spacing,drilling the final hole position, drill drainage time and reasonable negative pressure are determined.The research results in Yangquan mine got good effects, which can provide a reference for other Chinese seam group mining area. However, due to the different geological conditions of each mine, other mine gas enrichment law and drainage program also requires targeted research. |
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