表土厚度对浅埋工作面采空区自燃的影响规律

鄂尔多斯地区的煤层埋藏浅,表土层厚度对地表漏风影响明显,继而导致采空区的自燃危险区域发生变化。为此以某煤矿4201工作面为研究对象,先通过二维离散单元程序UDEC模拟确定地表与采空区连通时的表土层厚度范围,再根据该模拟结果建立不同表土层厚度条件下的采空区漏风模型,用Fluent数值模拟软件对采空区自燃危险区域进行模拟。结果表明:当采空区上覆基岩厚度一定、表土厚度小于74 m时,煤层开采后地表裂隙会与采空区连通,从而导致地表漏风;表土层厚度越小,采空区自燃危险区域的范围和地表漏风量就越大,两者近似呈对数函数关系;地表漏风不但使采空区自燃危险区域的范围明显增大,而且使回风侧宽度大于进风侧宽度。

Study on the influential regularity of the epipedon depth on the spontaneous combustion of the shallow face goaf

This paper takes it as a target to investigate the influential regularities of the Epipedon depth on the spontaneous combustion of the shallow face goaf by taking No.4201workface of a mine,as a study case sample.Since the amount of the surface air leakage has been found influenced by the thickness of the top soil,we have adopted a software known as the Universal Distinct Element Code (UDEC) to simulate the extension and expansion of the crack at the different degrees of the thickness of the top soil layer wherein the coal seam has been mined.Actually,the maximum thickness of the top soil layer has been determined by the surface crack and the mining condition of the goaf,whereas the relation between the surface crack and the thickness of the top soil layer can be determined on the basis of the maximum thickness of the top soil layer through the UDEC simulation by means of a goaf and surface air leakage model.We have also adopted a so-called Fluent simulation software in hoping to simulate the spontaneous combustion danger zone of the goaf at the different degrees of the thickness of the top soil layer.In do doing,the simulation results have been used to compare the data of the measured oxygen concentration in the goaf at 74 m depth beneath the top soil layer,which can be found well matched with each other.What is more,analysis has also been done for the effects of the surface air leakage velocity on the distribution of the spontaneous combustion in the goaf for the different degrees of thickness of the top soil layer.According to the analysis results we have done,the surface crack has been found well connected with the goaf area after the coal seam being mined,when the thickness of the top soil layer is less than 74 m.Furthermore,it can also be found that,the less the thickness of the top soil layer,the less the distance between the surface crack and the top-soil face will be;and,the greater the scope of the goaf spontaneous combustion danger zone,the more serious the surface air leakage.Thus,the scope of the spontaneous combustion danger zone and the air leakage can be found in an approximately logarithmic function.And,so,the surface air leakage can not only make the scope of spontaneous combustion danger zone more serious than without the air leakage,but also tends to broaden the air return side beyond that of the intake.