广域电磁法在深埋隧道勘察中的应用研究

Application Research on the Wide Field Electromagnetic Method for Deep-buried Tunnel Investigation

研究目的:广域电磁法是一种适应艰险复杂山区勘察并满足工程勘察精度要求的大深度勘察方法,本文通过对广域电磁法基本原理和特点的分析,并通过九天山隧道多测线的勘察应用以及与音频大地电磁法和大地电磁法的成果对比,旨在研究广域电磁法在艰险复杂山区深埋隧道勘察中的效果。研究结论:(1)广域电磁法在本次勘察中,有效深度达到2. 8 km,完全满足大深度隧道勘察的需要;(2)本次工作最大发射电流达到20 A,对地形和地表不均匀体产生的静态效应进行了较好的压制;(3)通过和大地电磁法(MT)以及音频大地电磁法(AMT)的对比,浅部信息比AMT丰富,深部信息比MT丰富,纵向分辨率提高很多,可以实现大深度隧道全范围的精细化勘察;(4)广域电磁法有效进行了地层的精细化划分,推断了构造位置与倾向,提示了软弱风险区,适用于艰险复杂山区深埋隧道地质勘察。

Research purposes: The wide field electromagnetic method( WFEM) is a kind of large depth survey method which is suitable for difficult and complex mountainous area exploration and meet the requirement of engineering survey precision. Based on the analysis of the basic principles and characteristics of WFEM,through the investigation of the multi-line in Jiutianshan Tunnel and the comparison with the results of the audio magnetotelluric method( AMT) and magnetotelluric method( MT),this paper aims to study the effect of WFEM in deep buried tunnel exploration in difficult and complex mountainous areas.Research conclusions:( 1) The effective exploration depth was 2. 8 km in this survey,which fully met the needs of large-depth tunnel exploration.( 2) The maximum emission current adopted in this survey reached 20 A,which made a good suppression of the static effects caused by terrain and surface unevenness.( 3) Compared with the magnetotelluric method( MT) and the audio magnetotelluric method( AMT),the shallow information of WFEM is richer than that of the AMT and the deep information of WFEM is richer than that of the MT. The vertical resolution is much improved,which can realize the full-scale detailed survey of the large-depth tunnel.( 4) The WFEM effectively carried out the fine division of the stratum,inferred the structural position and tendency,and suggested the weak risk zone,which is applicable to the geological exploration of deep-buried tunnels in difficult and complex mountainous areas.