Study On The Influence Of "Three Zone" In The Goaf Under Buried Pipe In Fully Mechanized Caving Face

Fully mechanized sublevel caving is widely used in China. But high productivity leads to too much residual coal and space large in the goaf. Therefore, both of spontaneous combustion and large gas emission in the goaf are very severe.In this paper, risk of coal spontaneous combustion under the condition of gas extraction in the goaf of fully mechanized is researched,on the basis of charatersitics of goaf under gas drainage, law of gas emission and delivery in the goaf,porous media theory, division of "three zone" and the present research of numerical simulation. Both of effectiveness of gas extraction and influence of "three zone" are analysed under these situations that are the different face air quantity and different distance from drainage’s position to working face. The feasibility is verified by field measurement, directing the fire prevention and extinguishing in the gaof under gas extraction.In1502fully mechanized coal mine in zhenghang coal, the result shows that:(1) The effectiveness of gas control is not good by only increasing the air quantity, especially upper corner.The gas concentration in the upper corner is still above5%when the air quantity is2000m3/min.It also turns out that the maximum width of oxidizing zone in the goaf is gradually becoming large with the increase of air quantity;(2) There is the best suitable distance from drainage’s position to working face.The effectiveness of gas extraction is the best when the distance is15m from drainage’s position to working face. It also turns out that the maximum width of oxidizing zone in the goaf is gradually becoming large with the increase of distance.Meanwhile the maximum width of oxidizing zone in the goaf is also becoming large after taking drainage measure;(3) Taking gas effectiveness and distribution of "three zone" into consideration, the result is the best when the air quantity is1500m(?)/min and the distance is15m. it not only solves the gas in the upper corner,but also controls the maximum width of oxidizing zone in some extent.The gas control and spontaneous combustion is an intercooupling problem. because we should take not only effectiveness of gas extraction but also spontaneous into consideration.The research in the paper has an important significance for gas extraction and division of "three zone" in fully mechanized caving face.