坑道瞬变电磁全程高分辨成像研究

Mine tunnel excavations are often threatened by a variety of water inrush hazards. The transient electromagnetic method is widely used in detecting water ahead of tunnel because of its sensitive response to water-bearing body. Due to interference of device system and volume effect of exploration, the reserving power of the test result is weaken in detecting the spatial geo-electrical information. So, the extraction of the whole field data is firstly taken by removing the primary field and transient process through the theoretical and experimental study of device system interference. As a result, the reliability of test data is improved. Secondly, the exploration capability for the short-range of tunnel is improved by studying the corresponding interpretation method through the analysis of construction mechanism of the transient electromagnetic field in process of falling edge. Finally, based on the electrical distribution characteristics of coal strata, the stereo spread stack imaging method of apparent resistivity is proposed by studying the spatial intersection characteristics of transient field induced by different detection orientation. It can improve the detection accuracy of the long-range of tunnel. The technical innovation realized for the high resolution imaging of transient electromagnetic field in this study will provide technical support for coal mine water prevention and control.

矿井坑道掘进常面临各种突水隐患，直接危害到煤矿安全生产。瞬变电磁方法因对含水体响应敏感而广泛应用于坑道超前探水。实践表明，因装置系统干扰及勘探体积效应等影响，测试结果对探测空间地电信息的分辨能力不足。为此，本课题首先基于装置系统干扰的理论与实验研究，消除互感干扰及过渡过程影响，实现全场数据的有效提取，提高测试数据的可靠性；其次，通过下降沿建场机理分析，研究下降沿瞬变电磁场的解释方法，改善坑道前方近距离勘探能力；基于煤系地层的电性分布特点，研究不同探测方位瞬变电磁场的空间交汇特征，实现视电阻率扩散叠加立体成像，提高坑道前方远距离的探测精度。本课题的研究将创新性的实现坑道瞬变电磁场的全程高分辨成像，可为煤矿防治水提供技术支撑。

瞬变电磁法因对含水体响应敏感而广泛应用于矿井水害探测。因装置系统干扰及勘探体积效应等影响，测试结果对探测空间地电信息的分辨能力不足。本课题（1）通过斜阶跃全空间全程瞬变电磁场响应公式的推导，在考虑一次场和接收系统暂态过程影响的基础上，重建了仪器记录的感应电压数据，确定降低线圈互感是减小实测瞬变场有效分辨时间的主要途径之一，进一步优化和改进了瞬变电磁测试线圈，从而将瞬变场有效分辨时间从改进前的1.3ms减小到改进后的0.216ms，增强了瞬变电磁浅层勘探能力。（2）通过数值模拟和物理模型实验，确定下降沿瞬变场对浅层地电参数敏感，并给出了下降沿瞬变场视电阻率计算方法，为进一步改善坑道瞬变电磁近距离勘探能力提供了新方法。（3）通过不同层状地电模型的构建，模拟分析了不同探测角度情况下瞬变电磁场的分布特征，确定了烟圈理论的有效性，并基于此实现了视电阻率扩散叠加立体成像，有效提高了瞬变电磁中远距离勘探分辨率。现场探测试验表明，瞬变电磁探测结果较为可靠，能为矿井水害防治更好的提供技术支撑，进一步反映了课题研究成果较好地改善了坑道瞬变电磁对探测空间地电信息的分辨能力，有一定推广应用价值。