OCTEM法探测地下空间地质病害体的应用研究  

Detection of unfavorable geological bodies of underground space with opposing coils transient electromagnetic method

作　　者：杨旭东 席振铢[2] 龙霞 黄基文 YANG Xudong;XI Zhenzhu;LONG Xia;HUANG Jiwen(Department of House Property Management,Central South University,Changsha 410083,China;School of Geosciences and Info-physics,Central South University,Changsha 410083,China;Hunan 5D Geosciences Co.,Ltd.,Changsha 410025,China)

机构地区：[1]中南大学房产管理处,湖南长沙410083 [2]中南大学地球科学与信息物理学院,湖南长沙410083 [3]湖南五维地质科技有限公司,湖南长沙410025

出　　处：《铁道科学与工程学报》2024年第8期3434-3444,共11页Journal of Railway Science and Engineering

基　　金：国家重点研发计划课题(2022YFC2903404)。

摘　　要：城镇地下空间地质病害体造成地面塌陷事故时有发生,对人民群众的生命财产安全构成巨大威胁。采用地球物理方法探测和预报地下空间地质病害体是预防城镇地面塌陷事故的重要方案。瞬变电磁法(TEM)是探测地下空间地质病害体的重要方法之一。等值反磁通瞬变电磁法(OCTEM)采用免接地、小体积、弱耦合的收发一体小型天线,便于在城镇硬化地面及施工空间受限的场地进行快速探测。本文结合理论计算和实际应用来研究OCTEM对地下地质病害体的探测能力。首先基于矢量有限元实现OCTEM三维正演,研究不同地电类型地质病害体的OCTEM响应特征。根据地下地质病害体的电性特征,构建了纯低阻型、纯高阻型、低阻-高阻复合型3类地质病害体地电模型,对比分析不同地电类型的地质病害体的异常响应,并计算包含地质病害体时的响应与不包含地质病害体时的背景响应之间的相对异常。计算结果表明:OCTEM对纯低阻型和低阻-高阻复合型地质病害体比较敏感,对纯高阻型地质病害体相对不敏感。对于低阻型或低阻高阻复合型地质病害体,低阻部分与围岩电阻率差异越大、厚度越大、埋深越浅,则相对异常越大,越容易被探测。随着深度加大,OCTEM探测分辨能力将减小。最后,通过在湖南浏阳某村镇试验剖面探测地下岩溶地质病害体案例,分析OCTEM的探测效果。Ground collapses caused by unfavorable subsurface geologic bodies occur frequently,posing a significant threat to the safety of people’s lives and property.The detection of unfavorable subsurface geological bodies by non-invasive geophysical method is an important scheme to reduce urban ground collapse.The transient electromagnetic method(TEM)is one of the important methods.The opposing coils transient electromagnetic method(OCTEM)applies small and weak coupling coils configuration which is free of grounding and requires limited operational space,making it suitable for shallow subsurface detection in urban areas.In this paper,theoretical calculation and actual tests were carried out to study the OCTEM responses of subsurface unfavorable geological bodies.According to the electrical characteristics,three types of unfavorable geological bodies were constructed,i.e.,they were resistive,conductive,and complex types.The relative anomaly between the abnormal response and the background response was calculated.The results show that OCTEM is sensitive to the pure conductive and the complex types,but not sensitive to pure resistive type.Under the same other conditions,the more conductive of the abnormal body is,the greater the thickness and the shallower the burial depth,the larger the relative anomaly is.As the depth increases,the detection resolution of OCTEM decreases.Finally,a karst detection case in a town of Liuyang City of Hunan Province was presented to show the result of OCTEM detection in unfavorable geological bodies detection in urban area.

关 键 词：等值反磁通瞬变电磁法 探测 地下空间 地质病害体 相对异常 

分 类 号：P631.3[天文地球—地质矿产勘探]