顶板导水通道瞬变电磁响应特征及应用

Transient electromagnetic response characteristics and application of roof water channel

针对西北干旱-半干旱矿区煤层顶板水害问题,为了查明回采工作面顶板导水通道分布范围,依据全空间瞬变电磁理论与时域有限差分算法,结合示范矿区地层电性特征建立正演地电模型,通过数值模拟研究了回采工作面顶板导水通道的不同磁场分量、不同时刻和不同探测角度的磁场响应特征,并在新疆示范矿区开展了应用试验。结果表明:线框法线方向所对应的磁场分量(Hy)强度最大,分布趋势最简单;磁场强度与衰减梯度随时间延迟逐渐衰减降低,在顶板导水通道处会产生二次感应,并以此为二次场源向外扩散衰减;Hy可识别顶板导水通道,最大有效探测仰角为75°;示范矿区的应用试验及后期钻探验证了瞬变电磁法在回采工作面顶板导水通道探测中的可行性与准确性。

Aiming at the problem of coal seam roof water disaster in arid and semi-arid mining areas in northwest China,in order to find out the distribution range of roof water channel in mining face,based on the whole space transient electromagnetic theory and the finite difference time domain algorithm,combined with the electrical characteristics of the strata in the demonstration mining area,a forward geoelectric model was established.The magnetic field response characteristics of different magnetic field components,different time and different detection angles of roof water channel in mining face were studied by numerical simulation,and the application experiment was carried out in the demonstration mining area of Xinjiang.The results show that the amplitude of the H_y magnetic field component corresponding to the normal direction of the wire frame is the largest,the magnetic field distribution trend is the simplest.The magnetic field intensity and attenuation gradient gradually decrease with time delay,and a secondary induction will be generated at the water channel of the roof,which will be used as the secondary field source to diffuse outward and attenuate.The H_y magnetic field component can identify the roof water channel,and the maximum effective detection elevation angle is 75°.The application experiment and later drilling in the demonstration mining area verify the feasibility and accuracy of the transient electromagnetic method in the detection of the roof water channel in the mining face.