煤矿区卸压瓦斯地面井破坏机理研究

Geological mechanism of failure surface vertical boreholes for relieved methane drainage in coal mining area

卸压瓦斯地面井抽采是矿区瓦斯治理的新方向,但受煤层采动影响,在工作面推过地面井一定位置后井孔迅速发生破坏,制约了其发展与应用推广。以淮南矿区抽采井变形破坏工程调查为基础,从工程地质学和采动岩体力学出发,探讨了矿区地质条件和煤层采动背景与抽采井变形破坏的关系。认为变形和错断是井身结构破坏的主要形式,该区地面卸压抽采井采动变形破坏具有时间快速性、空间集中性、破坏层位的层控性和破坏位置的岩性特殊性等四大特点。研究表明:卸压瓦斯抽采钻井的变形错断是在采动条件下,关键层诱导覆岩周期断裂致使覆岩移动,松散层中的特殊岩性层位或基岩段岩层的弯曲或断裂诱发的水平剪切破坏与岩层弯曲下沉引发垂向拉压综合作用的结果,并以前一种为主,而非单一剪断或拉断模式。另外,结合相似模拟实验结果分析,研究了开采条件下不同位置不同岩性地层的位移情况,证实了研究结论与观点,揭示了卸压瓦斯地面井井孔变形破坏机理。

The technology of relieved methane drainage by surface vertical boreholes has become a significant direction of coal mine gas utilization and control.It is,however,restricted by a serious problems of borehole damage in the production process.Previous papers and in-situ investigation are thoroughly reviewed in this paper.The relationship between geological conditions and mining effect background and borehole failure on geological engineering and mining rock mechanics is examined.A special kind of deformation and failure occurring near the interface of clay layer and lithological interface in some coal mines in the Huainan area in southeast China is described.The first part of this paper show that deformation and shear failure are the main forms of damage and some characteristics of them,such as chronological features,spatial distribution,formation features and lithological features,are discussed in order to illustrate qualitatively the mechanism of the deformation and failure.The authors ascribed the deformation and failure to a complex contribution of two modes,namely sliding geological conditions composed of special strata and lithology and rock movement which surrounds the well caused by mining subsidence.The second part of the paper concerns the physical simulation which has been used to verify the above-mentioned mechanism.