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煤层底板隐伏陷落柱突水机理及工程应用

Water Inrush Mechanism and Engineering Application of Concealed Collapse Column in Coal Seam Floor

  • 摘要: 华北煤田隐伏陷落柱难勘探、易突水、隐患大,是煤矿安全隐患的典型代表。以澄合矿区山阳煤矿1501工作面底板下隐伏陷落柱为工程地质背景,根据陷落柱的含(导)水特性,将突水事故分为整体剪切破坏和尖端劈裂破坏2种模式,结合高等岩石力学与断裂力学,分别建立突水力学模型,通过临界平衡条件与断裂判据,理论推导得到了底板隔水层可抵抗的临界水压解析解与隔水层厚度的安全阈值。结果表明,临界突水压力由2部分组成,即底板自身抵挡水压力值和围岩抵挡水压力值;临界突水压力与关键层厚度呈正相关,与陷落柱顶部宽度呈先减小后增大的关系;现场实际以陷落柱顶部宽度11.2 m为界,小于该值时极限水压力主要受控于有效隔水层厚度,大于该值时围岩水平应力对极限水压力影响较大;陷落柱周边裂隙扩展长度与水压力正相关,与覆岩压力负相关;陷落柱轴线角度在60°~90°更易诱发突水灾变。将研究成果应用于1501工作面底板危险性评价,理论分析给出了在受开采扰动影响下底板临界突水压力0.95 MPa不足以抵抗奥灰承压水压力1.2 MPa,且开采后陷落柱周边次生裂隙增长发育威胁陷落柱顶部隔水稳定性。根据陷落柱内部疑似的空洞,科学构筑了“堵水塞+双液注浆”处理方法,治理后工作面涌水量由65 m3/h降低至0.3 m3/h,工作面成功开采。

     

    Abstract: Concealed collapse column in North China Coalfield is difficult to explore, easy to water inrush, hidden dangers, is a typical representative of coal mine safety hazards. Taking the hidden collapse column under the floor of 1501 working face in Shanyang Coal Mine of Chenghe Mining Area as the engineering geological background, according to the water-bearing ( water-conducting ) characteristics of the collapse column, the water inrush accident is divided into two modes : overall shear failure and tip splitting failure. Combined with higher rock mechanics and fracture mechanics, the hydraulic model of water inrush is established respectively. Through the critical equilibrium condition and fracture criterion, the analytical solution of the critical water pressure that the floor aquifuge can resist and the safety threshold of the thickness of the aquifuge are theoretically derived.The results show that the critical water inrush pressure consists of two parts, namely, the water pressure value of the floor itself and the water pressure value of the surrounding rock. The critical water inrush pressure is positively correlated with the thickness of key strata, and decreases first and then increases with the top width of collapse column. When the width of collapse column top is 11.2 m, the limit water pressure is mainly controlled by the thickness of effective aquiclude when it is less than this value, and the horizontal stress of surrounding rock has a great influence on the limit water pressure when it is greater than this value. The fissure extension length around collapse column is positively correlated with water pressure and negatively correlated with overburden pressure. The collapse column axis angle between 60° and 90° is more likely to induce flood disaster. The research results are applied to the risk assessment of the floor of 1501 working face. The theoretical analysis shows that the critical water inrush pressure of the floor under the influence of mining disturbance is 0.95 MPa, which is not enough to resist the pressure of the Ordovician limestone confined water pressure of 1.2 MPa, and the growth and development of secondary cracks around the collapse column after mining threaten the stability of the water isolation at the top of the collapse column. According to the suspected cavity inside the collapse column, the treatment method of ' water plugging + double liquid grouting ' was scientifically constructed. After treatment, the water inflow of the working face was reduced from 65 m3/h to 0.3 m3/h, and the working face was successfully mined.

     

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