Method And Application Of Collaborative Control Of Gas And Coal Spontaneous Combustion In Gob Area With Entry Retaining By Roof Cutting

The non-pillar coal mining technology with gob-side entry retaining by roof cutting has been widely applied.Since there is serious air leakage between the gob-side entry roadway and the gob area,the risk of methane accumulation and spontaneous combustion of remnant coal may arise during the high-gas coal seam mining.Therefore,it is crucial for the promotion and application of this technology to realize the collaborative control of gas and coal spontaneous combustion in the gob area with entry retaining by roof cutting.This thesis constructs a similar simulation experiment platform with the engineering background of 4303 coalface in Shaqu II coal mine.Research methods including field investigation,theoretical analysis,similar simulation,and field test were adopted to investigate the collaborative control of gas and coal spontaneous combustion in the gob area with entry retaining by roof cutting.The main research results achieved are presented as follows:The concentration distribution and transport law of gas,and the distribution law of oxygen concentration and spontaneous combustion“three-zone”under various conditions including total inlet air volume,ratio of main and auxiliary inlet air volume,gas extraction method and extraction negative pressure,nitrogen injection parameters,and retaining wall tightness were analyzed to obtain the relevant optimization parameters.The reasonable total air volume at 4303 coalface was about 1800 m~3/min and the best ratio of main and auxiliary inlet air volume was about 2:1.The gas extraction method should focus on the high-level drilling and the extraction negative pressure should be controlled at about 20 kPa.Gas extraction by drilling in the middle-level caved zone and inserting pipes in the low-level retaining wall could be an auxiliary measure and the extraction negative pressure should be controlled at about 2 kPa.The reasonable location of nitrogen injection in the gob area should be on the main air inlet side of the coalface,60 m from the open-off cut,with a nitrogen injection volume of 1000 m~3/h.The laying speed and tightness of the retaining wall at the gob-side entry roadway had an important impact on the collaborative control effect.According to the results of the similar simulation study,the collaborative control method of gas and coal spontaneous combustion on the 4303 coalface was formulated and the control effect was examined.It was found that there was no phenomenon of gas concentration exceeding the limitation and coal spontaneous combustion during the mining in the coalface,which verified the results of the simulation experiment.The research results of this thesis have a guiding role in the application and promotion of the collaborative control of gas and coal spontaneous combustion in the gob area with entry retaining by roof cutting.The thesis has 63 figures,8 tables and 73 references...