The Research On Numerical Simulation Of The Gas Migration In The Comprehensive Mechanized Top-coal Caving Goaf

For the past few years, the comprehensive mechanized top-coal working face is in extensive use because it has the characteristics of high production and high efficiency, as well as low drivage ratio.But meantime, it also brings the characteristics of large gas discharge, unstabilized emission source etc, which lead to frequent transfinite gas in the working face, especially the upper coner of the working face has become the important and difficult points to gas control in fully mechanized caving face.So as to solve the problem of gas in the upper coner of the working face, analyzing and ensuring the affection degree of each influencing factor has become one of the key problems.Through observing ZhangCun coal mine and setting-out field data, as well as refering to specialistic empirical data, obtaining eight major factors that influence the gas density of the upper coner, which are gas emission quantity of the falling coal in the working face, the quantity of air volume in the working face, face-airing system, roof control mode of the working face, the commutative relation between the wind current of working face and the gas of working face, laneway section, air leak in the goaf, and all other factors. Utilizing gray relational grade theory to analyse the influence of each factor above-mentioned on gas of the upper coner, so as to find out that the main factor that influence the problem of gas in the upper coner of this working face is face-airing system.Using2203working face of ZhangCun coal mine as the research objective, on the basis of the law of conservation of mass, the law of conservation of momentum and the law of gas diffusion, establishing the mathematical model of gas migration in the working face goaf and the physical model which is consistent with the working face in the coal mine. Through using fluid mechanics software(FLUENT) to conduct numerical simulation on the gas in the goaf under different ventilation types such as "U" types "U+L" types、"U+I" type and "U+I+High-Level Entry" type, and compare the law of gas migration in the goaf under different ventilation forms, reaching a conclusion that by means of increasing air volume, the worker can effectively reduce the gas density of the upper coner under the ventilation type of "U", but under the ventilation type of "U+L" and "U+I", the gas concentration of upper corner reduces obviously, meanwhile, the gas concentration in the gas emission roadway is very high, which reaches to7.66%and6.5%.Under the ventilation type of "U+I+High-Level Entry", the function of taking out and in within the high end of Lane and drainage roadway makes high concentration gas in full mechanized coalface goaf migrate towards extraction entrance, so as to reduce gas in the goaf gushing towards working face, in return airway, the gas density is0.66%, within the high end roadway the gas density is around1%, the gas density of the upper corner is around0.65%, which accord with the related rules of＜＜Coal Mine Safety Regulation＞＞. On the basis of simulated results, the ventilation type of"U+I+High-Level Entry "can effectively manage the problem of gas in the working face of this coal mine, so as to provide basis for the gas management of the working face in the coal mine.