| During the “13th Five-Year”, China's coal industry will continue to adjust the direction of the integration of mergers and acquisitions, Large coal mine base occupies the leading position, especially the special thick coal seam mining area. Thick coal seam also use caving mining technology, mining intensity can achieve high efficiency and intensive production, but high intensity mining is often accompanied by high gas emission, for some areas such as Datong in Shanxi, also have the problem of gas abnormal emission in the presence of hard roof, it has a serious impact on the safe and efficient production of the mine.Aiming at the Tashan Coal Mine under the influence of hard roof caving face of abnormal gas emission problem, taking the 3-5# coal seam as the research object, through theoretical analysis, field experiment, data monitoring, simulation calculation method is studied in depth, the main conclusions are as follows:(1) Analysis of the working face of the gas source and the roof pressure of gas emission characteristics,the gas in the working face is composed of three parts of coal wall, coal mining and goaf gas emission. According to the monitoring data before and after the pressure,the gas source is calculated with the help of the Gauss smoke plume diffusion model.The results show that during the normal coal mining, the gas emission from the coal wall, coal falling and goaf was 3.46%?43.89% and 52.65%respectively, during the pressure, the coal wall, the coal mining and the goaf gas emission in the coal mining area each accounted for 4.9%?31.58% and 63.52%;According to the calculated concentration and air flow,the pressure cause the increase of 1.5~3m3/t emission of coal wall gas, and the goaf gas emission increased 15~30m3/min;(2) Based on the principle of aerodynamics and Newton's second law, the relationship between the gas emission and the roof load, the height of the goaf and the area of the roof were analyzed. Coupling the model of roof caving and gas emission, analyzed by COMSOL multiphysics coupling software,the result show that the impact of roof caving making the goaf gas flow to working face in a short time, and under the influence of wind, the gas flow to return airway, causing the upper corner, return airway and high drainage roadway gas concentration increases and then decreases sharply. According to the change of gas concentration, it can be known that the drainage area is mainly through the high extraction lane, the upper layer of hard roof falling is more than the hard roof of the lower layer to create a greater amount of gas emission, and the upper corner gas concentration change is most obvious, more likely to cause gas overrun;(3) Based on the theory of "O" mode, the characteristics of the fracture field in goaf are analyzed, the model of gas migration in the goaf was established, using FLUENT to simulate and analyze the goaf gas migration and enrichment law. In the horizontal direction, the goaf gas from the inlet side to the air return side rises gradually,working face to goaf deep gradually increased;From the vertical view, due to the effect of gas, the gas concentration is gradually increased from the bottom to the top. Gob gas enriched in deep goaf and return air roadway side and the concentration is higher than 40%,the distribution of gas concentration in the goaf is changed by the high pumping lane, a large number of gas emission through high pumping Lane,at the same time because of the negative pressure drainage effect, the air return side gas concentration reduced effectively, the return air lane and the upper corner gas concentration played a good control effect. |
PDF Full Text Request