基于电磁波传播的采空区AMT探测与异常快速圈定——以云南东川烂泥坪铜矿区为例

AMT detection and anomaly rapid delineation of goaf based on electromagnetic wave propagation:a case from Lanniping copper mine area in Dongchuan,Yunnan

为了研究电磁波的传播在采空区界面上发生反射和透射后对音频大地电磁测深(简称AMT)勘探的影响,模拟采空区推导出基于4层介质模型的阻抗计算公式。经过计算分析,采空区会引起AMT的电阻率和阻抗参数在高频段出现震荡,可利用高值异常波动来定性判断采空区。根据东川烂泥坪铜矿已知采空区的AMT探测资料,采空区引起视电阻率和阻抗在15~30 kHz频段出现高值异常,相对于视电阻率资料,阻抗对异常的反映更明显。提出采用阻抗平均法和最大阻抗法计算相对偏差,通过高值异常对采空区进行快速圈定。研究结果表明:2种方法得到的结果较为相似,基本符合实际采空区的分布情况,而最大阻抗法更适合采空区AMT探测使用。

In order to study the influence of reflection and transmission of electromagnetic wave propagation on the interface of goaf on the Audio Magnetotelluric(AMT)exploration,the impedance calculation formula based on four-layer medium model was deduced by simulating the goaf.After calculation and analysis,the goaf would cause the resistivity and impedance parameters of AMT to fluctuate in the high frequency band,and the abnormal fluctuation of high value could be used to qualitatively judge the goaf.According to the AMT data from the known goaf of Lanniping copper mine in Dongchuan,the goaf caused high value anomalies of apparent resistivity and impedance in the frequency band of 15~30 kHz.Compared with the apparent resistivity data,the impedance reflected the anomaly more obviously.It was proposed to use the impedance average method and the maximum impedance method to calculate the relative deviation,and the goaf could be quickly delineated through the high value anomaly.It showed that the results obtained by the two methods were relatively similar,which basically conformed to the distribution of the actual goaf,and the maximum impedance method was more suitable for AMT survey in the goaf.