Study On Gas Emission Law And Extraction Technology Of Fully Mechanized Caving Face In Tashan Mine

The gas disaster is one of the main obstacles in the intensive production process of super-large mines.Containing disasters caused by gas overruns remains the main task of mine safety production,gas extraction is the most effective and common gas control method available today.This thesis is aimed at the typical problem of“low gas occurrence and high gas emission”in fully mechanized caving face of super thick coal seam in Tashan Mine,taking the gas control of 8214 fully mechanized caving as the research background,through the on-site spot measurement and data visualization technology based on MATLAB software,the 3D visualization of the gas distribution characteristics of the working face is carried out,and the gas emission ratio of each part of the working surface is obtained.The theoretical analysis and numerical simulation based on 3DEC software are used to study the distribution characteristics of overlying rock fissures in goaf.Based on the distribution characteristics of overlying rock fissures,the flow field model of goaf based on FLUENT is constructed to study the gas migration and enrichment in goaf.In order to verify the accuracy of the above-mentioned research results,the technology of extracting goaf gas with large diameter directional long borehole is put forward,and the main controlling factors of extraction effect(extraction negative pressure and layout horizo)are simulated and analyzed by using FLUENT software.The engineering practice was carried out on the 8208 working face and the gas extraction effect analysis was carried out.According to the analysis results of on-site measured data,the main source of gas emission from the fully mechanized caving face of Tashan Mine is the goaf,with a ratio of 78.2%.According to the theoretical analysis and 3DEC software simulation results,the height of the overburden caving zone in the goaf is 28.3±2.5m,and the height of the fracture zone is52±5.6m,and the collapse angle of overlying rock is55°.Simulation results of gas transport in goaf based on FLUENT software,under the action of multiple factors,the gas in goaf is mainly enriched in the area near the air-return of the goaf fissure zone.The 1/4 area near the air-return of the goaf is the mian area of gas emission in the goaf.Through FLUENT software to control the analysis method of single variable,it is concluded that the reasonable extraction negative pressure of long-drilling extraction goaf is 15kPa,and the reasonable layout is 36m from the coal floor.Through the engineering practice of the 8208 working face,the average amount of gas extracted by large diameter directional long borehole is17.1m~3/min,the amount of gas extracted by pipe which buried in the upper corner is4.29m~3/min~8.25m~3/min,the gas extraction rate of working face is 69%~81.7%,and the gas at the upper corner of the working face is controlled at about 0.4%.The successful application of gas extraction technology of large diameter directional long borehole in goaf verifies the accuracy of the research results of gas emission rule in fully mechanized caving face of Tashan mine.It provides technical support for gas control in fully mechanized caving face of super thick coal seam in Tashan mine.