Research On Adaptability Of The Fully-mechanized Coal Mining Technology With Large Cutting Height In Dahaize Coal Mine

Coal industry is one of important pillar industry relating to our national economy, and coal still occupies main position in China energy structure during a long period. With the increase of mechanization degree, the work efficiency is greatly improved for the thick coal seam by using the fully mechanized mining technology with large cutting height. But, the coal wall falling frequently occurs in mechanized mining face with large cutting height, and the distance of tip-to-face is also increased. The probability of roof-rock flaking is greatly increased to influence the safety production of coal mine. Therefore, the studies on surrounding rock control theory and prevention & control technology are made not only to provide a scientific basis for the safety mining of similar coal seam, but also to enrich and develop the mine pressure control theory, and the level of disaster prevention is also improved.In this paper, base on the geological characteristics and actual production of Dahaize coal mine, the literature search, field measurement, laboratory simulation, theoretical analysis, numerical computation and field application were synthetically applied to analyze the adaptability and feasibility for No.2 coal seam by using the fully mechanized mining technology with large cutting height.Firstly, according to characteristics of working face with large cutting height, comprehensively considering all aspects of coal seam geological conditions, mining technology, safety technology and economic social benefit, the index evaluation system was presented for mining program selection of coal seam with large cutting height based on the analytic hierarchy process (AHP). The model of fuzzy comprehensive evaluation was also presented by applying the fuzzy mathematics and matrix analysis theory. Then, the relative index weights in the index evaluation system were solved through using the software Matlab and program compilation. According to the site actual conditions, the mining schemes including fully mechanized sub-level caving mining, fully mechanized sub-level caving mining with large cutting height and fully mechanized coal mining technology with large cutting height were evaluated and analyzed by applying the evaluation model, and it was the most reasonable to apply the fully mechanized coal mining technology with large cutting height for the No.2 coal seam of Dahaize coal mine.Secondly, through field observation and theoretical analyses, the stability of surrounding rocks was studied for the mechanized mining face with large cutting height and the falling mechanism of brittle coal body was discussed, and the impact factors of equipment reliability were also analyzed. Simultaneously, based on the testing and analysis for the physical and mechanical parameters of coal-rock, the mechanical model of coal wall caving of large cutting height was presented to deeply analyze the relationships between the coal wall caving depth of working face with large cutting height with the strength of underground pressure. Based on fully considering a correction coefficient of coal wall caving, the forecast model was established for the coal wall caving degree of working face with large cutting height, and the position of coal wall caving was 2.67m distance from roof and the range of caving depth was about 2.0-2.61m for the mechanized mining face with large cutting height of No.2 coal seam in Dahaize coal mine.Thirdly, through the theoretical analyses, the mechanical model of support and coal rock was presented for the working face with large cutting height, and the laws of first and periodic roof pressure were mastered. While the working face with large cutting height was advanced 40-60m in Dahaize coal mine, the basic roof would take place the first roof pressure. The height of roof caving zone was 69m, and that of fractured zone was 118m. After the first roof pressure of basic roof, there was stress concentration at 6-7m ahead of coal wall, and the coal wall caving would obviously happen during the range. When the working face was advanced 260-320m, the terrene was sufficiency exploiting.Lastly, through the theoretical analysis, observation of underground ressure, similar simulation and comparison with the seam-type mine, the technological parameters of fully-mechanized working face with large cutting height were confined for Dahaize coal mine. The cutting depth of the shearer in the working face is determined as 865mm. The strike length was 7000m and the length of working face was 320m, and the annual output would reach 1350Kt. Simultaneously, the supporting resistance of support was computed during the process of working face advancement. According to the roof convergence and active unloading amount of support, the parameters of shearer, scrape conveyor, hydraulic support and corresponding auxiliary equipments were determined for fully-mechanized working face with large cutting height in Dahaize coal mine. Through implementing scheme and applying the designed equipments, the safety mining of fully-mechanical working face with large cutting height would realize in Dahaize coal mine, and the good economic and social benefits were obtained.