瞬变电磁探测土质堤坝渗漏病害的正演模拟与工程应用

Forward simulation and engineering application of transient electromagnetic detection of soil embankment leakage disease

摘要

渗漏是土质堤坝的高发病害，瞬变电磁法有望实现堤坝深部渗漏低阻区的高效探测。采用有限元方法正演模拟了瞬变电磁场在堤坝内部扩散过程，揭示了瞬变电磁测量曲线对渗漏低阻区域的响应规律，量化分析了有、无渗漏通道磁感应强度的变化，最后结合实际工程开展了现场试验。结果表明：瞬变电磁场在堤坝内部呈椭球形扩散，渗漏低阻区使特定采样时间窗口的磁场分布相对集中、磁感应强度大幅增大，在多测道图上呈现为局部上凸型且表现出明显的体积效应；响应过程中，磁感应强度呈对数型降低，采用相对偏差值可凸显堤坝内部渗漏低阻区的响应；经现场试验和钻孔取芯比对，瞬变电磁法能够有效探测渗漏低阻区，相对偏差值多测道图和视电阻率图谱能够直观展示堤坝内部低阻分布区域。

Abstract

Leakage is a frequent disease in earthen dykes. Transient electromagnetic method is expected to achieve high efficiency detection in the low resistance area of deep seepage in dykes. The finite element method is used to simulate the diffusion process of the transient electromagnetic field inside the dam, reveal the response law of the transient electromagnetic measurement curve to the low resistance area of leakage, quantify the change of the magnetic induction intensity of the channel with and without leakage, and finally carry out field tests combined with practical projects. The result show that the transient electromagnetic field diffuses ellipsoid inside the dam, and the magnetic field distribution is relatively concentrated and the magnetic induction intensity increases greatly in the low-resistance area of leakage during a specific time period, which presents a local convex shape and obvious volume effect on the multi-channel map. In the process of response, the magnetic induction intensity decreases logarithmically, and the response of the leakage area in the embankment can be highlighted by using the relative deviation value. Through field test and comparison of core drilling, the transient electromagnetic method can effectively detect the low resistance zone of leakage, and the multi-channel map of relative deviation value and apparent resistivity map can directly show the distribution of low resistance zone inside the dam.

关键词

堤坝渗漏 / 瞬变电磁法 / 多测道图 / 数值模拟 / 工程应用

Key words

dam leakage / transient electromagnetic method / multichannel map / numerical simulation / engineering application

基金资助

国家重点研发计划(2021YFC3090103)

广东省水利科技项目(RS2023-02)

南京市水务科技项目(202404)