矿井全空间孔中瞬变电磁响应积分方程法数值模拟研究

基于地面-钻孔瞬变电磁法，将发射源布设于煤矿巷道中，而将接收探头放置在钻孔内，从上至下依次观测，形成矿井巷道-钻孔瞬变电磁法.为了研究巷道全空间条件下巷道-钻孔瞬变电磁场的响应特征，选取煤层底板受水害威胁的代表性地层为研究对象，建立煤层底板存在含水低阻地质异常体的三维数学模型，采用积分方程法进行数值模拟，结果表明：相对高阻的煤层侧帮对孔内垂向感应电动势的影响较小，而对孔内水平感应电动势除浅部约30 m内影响相对较大外，对深部影响较小.当煤层底板含水平低阻板状异常体时，在对异常体的纵向分辨率和异常响应的延续时间方面，孔内感应电动势的水平分量相对优于垂向分量，但垂向感应电动势的幅值强于水平感应电动势.因此，实际观测时，不仅要观测孔内感应电动势的垂向分量，也要观测水平分量.

Numerical simulation of drillhole transient electromagnetic response in mine roadway whole space using integral equation method

Borehole transient electromagnetic method (BHTEM) is operated in mine roadway. The source of BHTEM is laid in mine roadway and receiver is placed in drill hole, observation is carried out in turn from top to bottom. In order to study the response characteristics of BHTEM in roadway whole space, numerical simulation is carried out using integral equation method (IEM) based on 3D mathematical model in which the representative stratum of the coal seam floor under the threat of water hazard is selected as the research object and coal seam floor contains water bearing abnormal body. The transient electromagnetic (TEM) response characteristics are analyzed. The numerical simulation results show that the coal seam on both sides of the roadway has little influence on the vertical induction electromotive force response, when its resistivity is greater than that of coal roof and floor. While it has relatively great influence on the horizontal induction electromotive force responses of stations located in the shallow part within 30 meters and it has little influence on the horizontal responses of stations located in the deep. When coal seam floor contains horizontal low resistivity plate-like abnormal body, the horizontal component of the induction electromotive force is relatively superior to the vertical component in drill hole in terms of vertical resolution and the duration of the abnormal response of the abnormal body. While the amplitude of the vertical induction electromotive force is stronger than that of the horizontal induction electromotive force. So, not only the vertical component of the induced electromotive force in the borehole but also the horizontal component needs to be observed in actual observation.