Study And Application About Prevention And Control Against Spontaneous Combustion In Close Distant Coal Seam

China’s coal resources have complex occurrence characteristics and face many difficulties in mining.Mine fire is one of the main natural disasters in coal mine production.The main coal producing areas in China are located in the northwest of China,and their resource occurrence characteristics are mainly characterized by shallow burial depth,short distance occurrence,low gas content and low degree of coal metamorphism.Although the occurrence conditions are conducive to the use of large-scale mechanized equipment,after the upper coal seam mining,the surface will collapse and connect with the goaf,which will cause surface air leakage and increase the probability of spontaneous combustion in the goaf.After the lower coal seam is mined,the direct roof of the lower coal seam collapses.Because the direct roof of the first caving cannot be fully filled with the goaf,the roof rock caving will continue to develop upward.Because of the small distance between the coal seams,the upper coal seam will be mixed with the roof rock and fall into the lower goaf until the goaf is filled or a relatively stable structure is formed.In this way,the upper goaf and the lower goaf together constitute a complex goaf with more complex internal structure.The three-dimensional space of compound goaf is bigger,the shape structure and internal gas flow field are complex,the total amount of coal left behind is more,and the degree of coal metamorphism is lower.The spontaneous combustion tendency is spontaneous combustion coal seam,and the spontaneous combustion period is short.It is very easy to spontaneous combustion in goaf when the working face meets faults or withdraws.Based on literature research and theoretical calculation and laboratory research,this dissertation walks along the technical research route of“Spontaneous combustion characteristics parameters studied in the State Key Laboratory-Determination of risk areas of spontaneous combustion in a goaf-Prevention and control technology of coal spontaneous combustion”,taking a closer-distant and liable to spontaneous combustion coal seam group in Northwest China as a target of study,in order to study prevention and control technology suitable for a closer-distant and liable to spontaneous combustion coal seam group.First of all,the programmed heating experiment,the shortest spontaneous combustion period experiment and the activation energy testing experiment of coal-oxygen complex reaction were carried out on the coal samples collected in the coal mine with spontaneous combustion tendency,in order to determine characteristic parameters and rules of spontaneous combustion such as the gas generated when spontaneous combustion and the laboratory critical value,the shortest spontaneous ignition period and the activation energy of chemical reaction.Secondly,taking a coal mine in Northwest China as an example,the research investigated the regularity of caving,migration and crack development of overlying roof after mining of a closer-distant spontaneous combustion coal seam group,and used a computer to simulate and analyze the distribution law of residual coal in goaf with roof caving.After that,through layering sampling points in several longitudinal boreholes in goaf,the gas in goaf can be monitored dynamically and stereoscopically in real time.According to the change of composition and concentration,the range of"three zones"of spontaneous combustion in goaf of close coal seam group is scientifically divided.Combining with the movement of roof in goaf and the distribution of residual coal,the dangerous area of spontaneous combustion in goaf is determined,which effectively reduced the key range of monitoring,prevention and control of spontaneous combustion in goaf.Finally,according to the characteristics of three-dismensional and stereo distribution of the oxidation zone in goaf,and based on the characteristics of the layered distribution of spontaneous combustion dangerous district in oxidation zones,comprehensive prevention technical measures such as multi-means monitoring based on landmark gas and critical value,combined grouting highly and lowly,nitrogen and liquid CO₂ injection,blockage of air leakage were adopted.After all,the prevention and control technology of spontaneous combustion of closer-distant coal seam has been established scientifically and effectively.