巨厚砂岩含水层下煤层群开采顶板突水机理研究

Study on roof water inrush mechanism of coal seam group mining under thick sandstone aquifer

为研究巨厚砂岩含水层下煤层群开采覆岩破坏及顶板突水机理,防止开采过程中出现突水事故,采用理论分析、流固耦合相似模拟、三维激光扫描等研究手段对导水裂隙发育、初次及周期来压、含水层内部渗流、工作面涌水量预测进行研究。结果表明:(1)下部煤层开采后,覆岩破坏剧烈,裂隙率显著增加至70.9%,导水裂隙异常发育至K3含水层底部;(2)重复采动会导致初次、周期来压步距明显缩短,且随着采动次数增多,来压频率逐渐升高;(3)在渗透压差和封闭离层空间负压的联合作用下,K3含水层的各向异性非均质低透特性导致其下部形成多个叠加的降落漏斗,出现非统一渗流场,内部不同层位水位降深有所差异,工作面涌水量总体可控。在此基础上,提出了优化回采参数的建议,为矿井后期实现安全高效生产提出切实有效的防治水措施打好基础。

In order to study the overburden failure and roof water inrush mechanism of coal seam group mining under thick sandstone aquifer,and prevent water inrush accidents in the mining process,theoretical analysis,fluid solid coupling simulation,three-dimensional laser scanning and other research methods are used to study the development of water flowing fractures,primary and periodic weighting,internal seepage of aquifer,and water inflow prediction of working face.The results show that:(1)after the mining of the lower coal seam,the overburden rock is severely damaged,the fracture rate increases significantly to 70.9%,and the water flowing fractures are abnormally developed to the bottom of K3 aquifer;(2)repeated mining will lead to the shortening of the initial and periodic weighting step,and the weighting frequency increases gradually with the increase of mining times;(3)under the combined action of the osmotic pressure difference and the negative pressure in the closed separation space,the anisotropic heterogeneous low permeability characteristics of K3 aquifer,leads to the formation of multiple superimposed downcomers in the lower part of the K3 aquifer,resulting in a non-uniform seepage field.The water level drawdown in different layers is different,and the water inflow of the working face is generally controllable.On this basis,the suggestion of optimizing mining parameters are put forward,providing a good foundation for proposing practical and effective water control measures for realization of safe and highly efficient production in the later stage of the mine.