GEM多频电磁在吉林市牤牛河泥砂分布测量的初步应用

Preliminary Application of GEM Multi-frequency Electromagnetic Method in Mud and Sand Distribution Measurementof Mangniu River in Jilin City

通过对GEM-2多频电磁仪方法技术介绍和测试分析,首次使用多频电磁仪进行泥砂分布研究。采用425~63 025 Hz按指数增加的5个频率,以平均线距60 m完成吉林市境内牤牛河棋盘村-江密峰镇一带垂直河道测线477条测量,涉及河道长约28.11 km,覆盖面积约1.17 km2。通过不同频率同相、正交、视电导率、视电阻率等值线平面图分析,不同频率反应不同的深度,能有效识别泥砂之间的电阻率差异。根据测量的多频数据进行了深度换算,结合一维反演推断含砂层在2 m、6 m和10 m左右,分别对应高频63 025 Hz、中频5 175 Hz和低频425 Hz探测的深度;再结合收集的资料和实地勘查,进行了区域地质及电性特征分析,推测河道沉积模型或第四系覆盖层模型,从而对牤牛河流域泥砂分布的位置及深度进行了初步划分,可为流域内土壤侵蚀防治、防洪除涝、泥沙治理、生态环境保护等提供相关的基础资料和参考。

Through the technical introduction and test analysis of GEM-2 multi-frequency electromagnetic instrument method,the multi-frequency electromagnetic instrument was used to study the sediment distribution.Five frequencies increased exponentially from 425 Hz to 63025 Hz,477 vertical river survey lines in the area of Qipan village-Jiangmifeng town of Mangniu River in Jilin city were completed with an average line distance of 60 m,involving a river about 28.11 kilometers long and an area of about 1.17 km 2 wide.Through different frequency in-phase,orthogonal,apparent conductivity,apparent resistivity contour map analysis,and different frequencies respond to different depths,Effective identification of resistivity differences between mud and sand.Depth conversion is carried out based on measured multi-frequency data,combined with one-dimensional inversion,it is inferred that the sand-bearing layer is about 2 meters,6 meters and 10 meters,corresponding to the detection depth of high frequency 63025 Hz,intermediate frequency 5175 Hz and low frequency 425 Hz respectively.The regional geological and electrical characteristics were analyzed which combined with the collected data and field investigation,and the channel sedimentary model or Quaternary overburden model was speculated.The location and depth of mud and sand distribution in Mangniu River Basin were preliminarily divided,which can provide relevant basic data and reference for soil erosion,flood control and waterlogging removal,sediment control and ecological environment in the basin.