工作面动压区穿层钻孔瓦斯抽采技术及其效果分析

Gas extraction technology and its effect analysis of perforating borehole in dynamic pressure zone of working face

为解决突出煤层瓦斯抽采困难,回采过程中仍易造成瓦斯异常涌出,以及底抽巷瓦斯抽采利用率不足的问题,采用FLAC3D数值模拟软件对工作面回采期间超前支承压力分布及塑性区发育情况进行模拟,根据数值模拟结果有针对性地在底抽巷开展动压区瓦斯二次抽采,并通过瓦斯体积分数检测和瓦斯纯量计量对二次抽采效果进行评价。研究结果显示,工作面前方0~7m范围内为塑性区,垂直应力对煤体起到主要的破坏作用,煤体裂隙发育贯通,易于抽采;可将距工作面0~20m、20~60m和60m外分别划分为高效抽采区、有效抽采区和原始抽采区,各区瓦斯体积分数随着与工作面距离的增加而减小,直至进入原岩应力区而稳定;通过对动压区二次抽采瓦斯纯量进行计量可知,采用穿层钻孔对工作面动压区瓦斯开展二次抽采工作能够提高瓦斯抽采效率,减少工作面瓦斯涌出量。

In order to solve the problems of gas extraction difficulty in outburst coal seam,abnormal gas emission during mining and insufficient utilization rate of gas extraction in bottom pumping roadway,FLAC3D numerical simulation software is used to simulate the distribution of advance abutment pressure and the development of plastic zone during mining of working face.According to the numerical simulation results,secondary gas extraction in dynamic pressure zone is carried out in bottom pumping roadway.The effect of secondary extraction is evaluated by measuring the volume fraction of gas and measuring the volume of pure gas.The results show that plastic zone in the range of 0-7 m in front of the working face,and the vertical stress plays a major role in destroying the coal body,and the cracks in the coal body are well developed and easy to be extracted.0-20 m,20-60 m and 60 m away from the working face can be divided into high efficiency extraction zone,effective extraction zone and original extraction zone,respectively.The volume fraction of gas in each area decreases with the increase of the distance from the working face,and becomes stable until it enters the original rock stress zone.Through the measurement of the volume of pure gas in the dynamic pressure zone,it can be seen that the secondary gas extraction in the dynamic pressure zone of the working face can improve the efficiency of gas extraction and reduce the amount of gas emission.