西山矿区地质异常体瞬变电磁响应规律研究

Study on transient electromagnetic response law of geological anomaly in Xishan mining area

通过数值模拟正演对西山矿区断层、陷落柱、灰岩含水层等典型的地质异常体模型进行了分析,得出地质异常体的瞬变电磁响应规律。研究结果表明:采用瞬变电磁法在井下巷道中探测断层时,断层面与掘进工作面端头激发源的距离对探测结果影响较大;探测含水层时,探测效果受到激发源所在岩层的厚度、电性特征,以及含水层电性特征、含水层与源点的距离的影响,含水层与邻近岩层的电性差异越大,探测效果就越明显;探测含水陷落柱时,感应电流密度中心逐渐向陷落柱中心移动,最后重合;不含水陷落柱的瞬变电感应电流密度中心向远离陷落柱的方向移动,直到完全衰减。陷落柱与激发源所在岩层应当存在一定的电性差异,激发源所在岩层的电阻率值至少应为陷落柱岩性电阻率值的2倍。

Through numerical simulation forward modeling, the typical geological anomaly models such as faults, collapse columns and limestone aquifers in Xishan mining area were analyzed, and the transient electromagnetic response rules of anomalies were obtained. The results show that when using transient electromagnetic method(TEM) to detect faults in underground roadway, the distance between the fault plane and the excitation source of the excavation face has a great influence on the detection results;when detecting an aquifer, the detection effect are affected by the thickness and electrical characteristics of the rock layer where the excitation source is located, as well as the electrical characteristics of the aquifer and the distance between the aquifer and the source point, and the greater the electrical difference between the aquifer and the adjacent rock layer, the more obvious the detection effect will be;when detecting the water-bearing collapse column, the center of induced current density gradually moves to the center of the collapse column and finally overlaps;the center of the transient electrically induced current density of the non-water-bearing collapse column moves away from the collapse column until the complete attenuation is completed. There should be a certain difference in electrical properties between the collapse column and the rock layer where the excitation source is located, and the resistivity value of the rock layer where the excitation source is located should be at least twice that of the lithologic resistivity value of the collapse column.