The Research On Numerical Simulation Of The Gas Migration Rules In The Caving Goaf

Over the recent decades, the caving mining has been widely applied in our country. As mechanized top coal caving is with the characteristics of high yield, high efficiency, and promoting at the fast speed so that the gas emissions are more concentrated and unbalanced, which often caused the gas overtime in the back air flow and the gas gauge on the corner, etc., which becomes the grave hazard for the safety production in the coal mines. Therefore, the research of the gas migration rules in the Caving goafs has greatly important theoretical and practical significance.According to the migration laws and characteristics of the goaf gas when the top coal is caved, through the FLUENT software the thesis researches on numerical simulation of the gas migration rules in the Caving goafs, and analyses the gas emission rules in the caving face and the influence factors in more detail, and expatiates the characteristics of the gas migration in goaf rising float, diffusion and aggregation; with the application of overlying strata theory, combining the situation of Cheng Colliery 2311 caving face, it confirms the height of the caving zone and fractured zone, establishes the foundation for the physical model of the gas migration in the Caving goafs.Through applying of the mass conservation rules, momentum conservation law and the diffusion law, using , the gas migration mathematics model is established in the caving goafs, by using FLUENT software the numerical value of the gas migration in U-ventilation face is simulated, the contribution rules of the gas concentration in goaf obtained, that is, towards the direction, the gas concentration increases gradually with much deeper distance, towards the tendency direction from the inlet side to the return air side the gas concentration gradually increases, in the vertical direction with the height increasing the gas concentration gradually increases, which provides a reliable theoretical gist for the gas control in goaf. By the numerical simulation and comparision, the six cases of U-type, W type, U + L-type, U + I, double U-, U + I + towards high Roadway and U-, W-type ventilation work face under different wind flow, the gas concentration distribution in caving face is comparatively analysed, the results show that: For the W-type ventilation on the face with air volume of 1440m3/min, the gas concentration on the middle face is 10.4%, comparing U-ventilation the gas concentration in the upper corner is 12.2%, while the gas concentration decreased. By increasing the air volume in U-and W type ventilation goafs, the gas concentration in the upper corner and the central goafs can be reduced; U + L, U + I-type ventilation can decrease the gas concentration of the goaf, significantly decreases the gas concentration in the return air Lane and the upper corner, but the gas concentration of Tail exceeds; Aimed at the Caving goafs with high production and high efficiency, which are large output and big gas emission, double U-ventilation can efficiently solve the gas exceeding problem in the back Wind Lane and the upper corner whose concentration are separately 0.45% and 0.65%.The function of taking out and in within the high end of Lane and Drainage Roadway of the U+I+high Roadway makes the high concentration gas in the caving goafs transport to the extraction port, which reduces the gas emission in the goaf towards working place and can effectively solve the gas exceeding problem in the air Lane and Upper Corner of the caving goafs whose concentration separately are separately 0.6% and 0.65%.