基于D-P准则的煤层钻孔封孔深度分析

为了确定合理的煤层钻孔封孔深度，提高瓦斯抽采效果，基于D-P屈服准则，提出关于中间主应力、煤岩剪膨胀的巷道开挖模型，推出钻孔周围煤体应力应变及钻孔封孔深度表达式。结合工程实例，以煤巷掘进工作面平均瓦斯抽采浓度和钻屑量为基础进行封孔深度的验证。研究结果表明:中间主应力、残余黏聚力、内摩擦角和剪胀角对于封孔深度有重要影响；在一定区间内，钻孔封孔深度随中间主应力的增大而增加，超过某个值后会随着中间主应力的增加而减小；剪胀角越大，扩容系数越大，钻孔封孔深度越大；平均瓦斯抽采浓度和钻屑量测试结果验证了封孔深度的准确性。

Analysis on sealing depth of borehole in coal seam based on D-P criterion

In order to determine the reasonable sealing depth of borehole in coal seam and improve the effect of gas drainage, a roadway excavation model of intermediate principal stress and coal rock dilatancy was put forward based on the D-P yield criterion, and the expressions of coal stress and strain around the borehole and sealing depth of borehole were deduced. The verification of sealing depth was carried out based on the average gas drainage concentration and drilling cuttings quantity in the driving working face of coal roadway combined with the engineering case. The results showed that the intermediate principal stress, residual cohesion, internal friction angle and dilatancy angle had important influence on the sealing depth. In a certain range, the sealing depth of borehole increased with the increase of the intermediate principal stress, and decreased with the increase of the intermediate principal stress when exceeding a certain value. The larger the dilatancy angle, the larger the dilatation coefficient, and the larger the sealing depth of borehole. The accuracy of sealing depth was verified by the test results of average gas drainage concentration and drilling cuttings quantity.