黄河流域中上游煤炭资源的大规模开发已造成生态环境的持续恶化，掌握煤炭开采对地下水系统的影响规律有助于实现煤炭资源开发与生态环境保护的协调发展。以陕北柠条塔煤矿南翼为研究区，通过地质与地电条件的分析，建立了地电模型；基于时域电磁场理论，模拟分析了正常（不含水）和异常（局部含水）地电模型条件下瞬变电磁场的扩散过程和发射回线中心点电压曲线的衰减特征，结果反映10ms范围内含水异常体的瞬变电磁场响应明显，且不同层位含水体的响应时间和幅值有较大差异，从理论上表明了利用瞬变电磁法探测研究区地下水的可行性。针对研究区测试条件，结合数值模拟和现场试验结果，确定选择25Hz的发射频率有利于瞬变电磁场衰减早、中期数据的获取。通过对研究区地层的瞬变电磁场动态监测，对比分析了2-2煤层开采前后地层在纵横向上的电性变化特征，表明煤层开采总体上降低了直罗组（J2z）和延安组（J2y5）岩层的富水性，且相对富水区位置从采前的中至北部变化为采后稳定期的东北部，指出富水性的变化与地层结构的改变、上覆土层隔水性能的变化以及地下水补给等密切相关，进一步反映了煤炭开采对地下水系统具有显著影响。最后，讨论认为瞬变电磁动态监测结果有一定的局限性，应进一步综合研究区其它成果从整体上揭示煤层开采对地下水系统的影响规律，从而为该矿区生态环境保护与修复提供参考。

Large-scale exploitation of coal resources in the upper and middle reaches of the Yellow River basin has caused the continuous deterioration of ecological environment.It is helpful to realize the coordinated development of coal resources exploitation and ecological environment protection to understand the influence law of coal exploitation on groundwater system.Taking the south wing of Ningtiaota Coal Mine in Northern Shaanxi as the study area,the geoelectric model is established by analyzing the geological and geoelectric conditions in this area.Based on the time domain electromagnetic field theory,the diffusion process of transient electromagnetic field and the attenuation characteristics of voltage curves at the center of exciting loop under normal (no water) and abnormal (local water) geoelectric model conditions are simulated and analyzed.The results show that the transient electromagnetic response of water-bearing anomalies within 10 ms is obvious.Moreover,the response time range and amplitude of water-bearing anomaly in different layers are also greatly different.Thus,the feasibility of using transient electromagnetic method to detect groundwater in the study area is demonstrated theoretically.According to the site test conditions and combining with the results of theoretical simulation and field measurements in the study area,the transmission frequency of 25 Hz is determined,which is conducive to the acquisition of transient electromagnetic field data in early and middle stage.Through the dynamic monitoring of transient electromagnetic field of the strata,the characteristics of vertical and horizontal resistivity of strata are compared and analyzed.The laws,that coal mining generally reduces the water bearing capacity of the overlying J2z and J2y5 strata,and the relative water rich areas change from the central and north parts before mining to the northeast parts during the stable period after mining,are revealed.At the same time,it is pointed out that the laws are closely related to the flow direction of groundwater,the change of the stratum structure and the variation of overlying soil water insulation property and so on,which further reflect the significant influence of coal mining on groundwater circulation system.Finally,considering the limitations of the transient electromagnetic monitoring results,it is necessary to further integrate other results to reveal the influence law of coal mining on groundwater system as a whole,so as to provide a reference for ecological environment protection and restoration in the mining area.

1 研究区地质与地电特征

2 瞬变电磁场正演模拟

   2.1 电磁场正演理论

   2.2 瞬变场响应分析

3 瞬变电磁动态监测

   3.1 观测布置与参数选择

   3.2 采动前后地层富水性变化特征

4 结论