水下采煤覆岩裂隙扩展判断方法及其应用

Study on crack expansion judgment method in overlying strata and its application for coal mining under aquifers

工作面突水是影响水体下煤层安全开采的主要隐患,而上覆岩层导水裂缝带发育是引起工作面突水的基本路径。基于裂隙萌生发育的形态分析,将导水裂隙带划分为两种类型,一是原生裂隙的张开或滑动,二是新生裂隙向完整结构的扩展;而且,在工程荷载作用下卸荷裂隙的萌生和扩展具有优势定向性特征。考虑开采煤层覆岩裂隙的分布特征,基于格里菲斯摩尔-库伦准则建立了裂隙扩展的分析模型和判断方法。借助FISH语言,将扩展模型耦合入离散元软件UDEC中,并用其模拟水体下煤层开采过程,分析在工作面推进过程中上覆岩层内裂隙带萌生演化特征。分析了工作面突涌水机理,得出了水下采煤工作面覆岩导水裂隙带高度的确定方法。并结合导水裂隙带高度现场观测实践进行了工程验证。

The safety of coal mining under aquifers is significantly affected by the risk of a water inrush into the mining face,while,the falling of overlying rocks and propagation of fractures are major factors for water inrush. In the paper,the propagation cracks was divided into two basic categories. One was the opening or sliding of original cracks,and the other was the extension of new cracks to the complete structure. Such analyses indicate that the stress-release crack induced by coal mining shows obvious characteristics of parallel or perpendicular to the free surface. An analysis model and corresponding judgment method was proposed considering the characteristic of crack propagation based on the principles of Griffith and Mohr-coulomb. A secondary exploitation of the 2-dimensional distinct element program( UDEC4. 0) was carried out in virtue of the inner-embed FISH language,and it was used to simulate the process of coal mining under aquifers,to analyze the generation and evolution of fractures in overlying strata with the advance-ment of mining face. Further researches have been done on the formation mechanism of water inrush into mining face.The height computation method for water flowing into fractured zone is obtained. They were confirmed by the observational practices of field engineering.