流量考察钻孔数量对有效抽采半径的影响

Analysis of the influence of the number of boreholes on the drainage radius flow investigation method

有效抽采半径是煤层预抽钻孔合理布孔间距的依据。目前煤层顺层瓦斯抽采钻孔有效抽采半径较多采用流量法测定,现有标准规定考察钻孔数量不少于4个,但未就考察钻孔数量对有效抽采半径测定结果的影响开展试验研究,笔者通过在云南省镇雄县大营煤矿5号煤层+1150 m标高1503轨道运输巷布置三组15个顺层试验钻孔采用流量法考察5号煤层有效抽采半径,其中第一组4个钻孔,钻孔间距4 m,考察半径2 m,第二组5个钻孔,钻孔间距3 m,考察半径1.5 m,第三组6个钻孔,钻孔间距2 m,考察半径1 m。结果发现:当钻孔直径为75 mm,抽采时间为30 d,抽采率为30%,抽采负压34~38 kPa左右时,考察钻孔数量分别为4、5、6个时,得到有效抽采半径分别为1.53 m,1.54 m,1.65 m(结果统一取两位小数),5号煤层有效抽采半径随着钻孔数量的增加而增大,所得有效抽采半径差异系数为3.50%。

Effective extraction radius is the basis of reasonable spacing of pre-extraction boreholes in coal seams.At present,the effective extraction radius of boreholes along the the formation is mostly measured by the flow method with the boreholes number of not less than 4 according to the existing standard,but the influence of the number of boreholes to the measurement results of effective extraction radius has not been studied experimentally.The author proposes the flow method to investigate the effective extraction radius of No.5 coal seam by laying three groups of 15 test holes in 1503 track transportation lane with+1150 m elevation in Daying Colliery of Zhenxiong County,Yunnan Province,in which the first group consists of 4 holes with the hole spacing of 4 m and the investigation radius of 2 m,the second group 5 boreholes with a spacing of 3 m and a radius of 1.5 m and the third group 6 boreholes with a spacing of 2 m and a radius of 1 m.The results showed that when the borehole diameter is 75 mm with 30 day extraction time,30%the extraction rate and 34~38 kPa negative extraction pressure,the effective extraction radius is 1.53 m,1.54 m,and 1.65 m respectively when the number of boreholes is investigated as 4,5,and 6 respectively;the effective extraction radius increases with the increase of the number of holes with the difference coefficient of effective extraction radius of 3.50%.