CCTEG Coal Industry Planning Institute

为探究软硬复合煤层瓦斯抽采钻孔的变形规律,采用自主研发的“一种全角度瓦斯抽采钻孔稳定性动态监测装置”进行了现场监测,系统分析了硬煤、软煤、软硬复合煤层瓦斯抽采钻孔的变形情况,并采用COMSOL数值模拟手段对试验结果进行验证,结果表明:钻孔浅部竖直方向应变敏感程度滞后于水平方向,且呈交替性增大特征;钻孔应变衰减阶段前,存在一种短暂的伪平衡状态,其实质是煤体内部应力集聚,后突然释放而造成钻孔塌孔;在相同的外部载荷条件下,软弱界面将软硬复合煤层分割为两个相对独立的应力环境,煤层在软弱界面处发生介质突变和应力突变;硬煤层钻孔较软煤层钻孔的各部位变形小,二者均表现为浅部变形大、深部变形小,最终达到稳定环向应变,软硬复合煤层穿层孔在浅部变形与二者相近,穿层孔深部和软弱界面交叉截割形成应力集中区,应力集中区范围沿软弱界面和钻孔径向同时延伸并逐渐衰减,这种衰减呈不明显的非线性特征。

In order to explore the deformation laws of gas extraction boreholes in soft and hard composite coal seams, a self- developed dynamic monitoring device for the stability of full-angle gas extraction boreholes was used for on-site monitoring. The deformation of gas extraction boreholes in hard coal, soft coal and soft and hard composite coal seam was systematically analyzed, and the test results were verified by COMSOL numerical simulation. The results show that, the vertical strain sensitivity of the shallow part in the borehole lags behind that of the horizontal, and the vertical and horizontal strain sensitivity increases alternatively. Before the strain decay stage of the borehole, there is a short-term pseudo-equilibrium state, during which the internal stress accumulates in the coal body, and then it releases suddenly causing the borehole collapse. Under the same external loading conditions, the soft and hard composite coal seam is divided into two relatively independent stress environments at the weak interface, and the sudden change of medium and stress occurs at the soft interface. The deformation of each part of the hard coal seam borehole is smaller than that of the soft coal seam borehole, both of which are characterized by large shallow deformation and small deep deformation, and finally achieve stable hoop strain, and the shallow deformation of the cross-bed hole of the soft and hard composite coal seam is similar to that of the two, and the deep part of the cross-bed hole and the weak interface are cross-cut to form a stress concentration area, and the range of the stress concentration area extends along the radial direction of the weak interface and the borehole at the same time and gradually attenuates, and his attenuation presents an insignificant nonlinear characteristic.

张栋,任朝朋.软硬复合煤层瓦斯抽采穿层钻孔变形塌孔特征规律研究[J].煤炭工程,2024,56(10):201-207.