天然电场选频法在充水岩溶勘查中的试验与分析

探讨了天然电场选频法在岩溶水灾害勘查中的地质效果和异常成因。在四川古叙煤田观文煤矿选定4处试验点，共敷设选频法测线11条，通过对各测线上采集结果的处理和分析，结合现场地形地质条件，推测各点地下充水溶洞的分布情况。根据选频法的解释结果与矿山前期地勘成果及后期运输巷道实际开挖情况的对比来看，该方法的解释结果是准确的，可在今后进一步将该方法应用于地下水灾害勘查，以便为矿山排水巷道、排水措施设计和地下水的安全防治提供科学依据。在实践应用的基础上，进一步从麦克斯韦方程组出发，对均匀谐变电磁场中低阻水平圆柱体的感应场进行理论推导和模拟计算，通过感应二次电场水平分量的模拟计算结果与实测曲线的对比，说明天然电场选频法的异常成因主要是由二次感应电场所致。 

Application and analysis of natural electric field frequency selection method for water-filled karst investigation

Geological effect of karst water prospecting by natural electric field frequency selection method and the cause of anomaly formation were discussed in this paper. Eleven exploration lines of frequency selection method were designed in four areas appointed by Guxu coal mine. Distribution of water-filled karst was predicted in working area by data processing and result analysis and in combination with the local topographic and geologic conditions. The geophysical interpretation result is credible from the comparison of geophysical results with geological exploration data and tunnel excavation data. This geophysical method can be used to investigate groundwater, and it is the scientific basis for the design of roadway and drainage, prevention and control of water hazards. On the basis of practice and from Maxwell equations, the author deduced the formula of induced electric field of a horizontal cylinder in homogeneous harmonious electromagnetic field, and calculated electric field intensity. According to the comparison of the horizontal component of induced natural electric field with the experimental curve, anomalies of frequency selection method are caused by induced secondary field.