Experimental Study on Dam Foundation Leakage Detection by Magnetoelectric Method Based on M Sequence
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摘要:
坝基渗漏问题是影响水库大坝整体安全的关键因素. 为有效、准确探测坝基渗漏,基于伪随机辨识原理,将M序列相关辨识的磁电法技术应用于堤坝渗漏探测. 首先,通过物理模型试验分析,获取不同渗漏深度下的磁感应强度分布、均方差及变异系数特征;然后,设计不同渗漏形态、高阻屏蔽层及渗漏通道数量条件,获取探测结果对倾斜通道、高阻屏蔽层以及多条渗漏通道的响应特征;最后,通过云南红石岩堰塞坝现场试验,分析该技术的可行性. 试验结果表明:在不同埋深条件下,磁感应强度最大值的变异系数均控制在2%以内;渗漏通道的倾斜引起磁感应强度沿渗漏方向缓慢降低,其磁场等值线图的脊线反映倾斜渗漏方向;高阻屏蔽层仅对磁感应强度产生影响,磁感应强度误差在10%~20%之间;多组渗漏通道会反映在磁场等值线图中异常场的多处集中分布;现场试验探测的渗流流向分别为NW300°,SW265°,W215°和NW305°.
Abstract:The dam foundation leakage problem has been a key factor affecting the overall safety of reservoir dams. To effectively and accurately detect dam foundation leakage, the magnetoelectric method based on M sequence correlation identification technology was applied to the dam leakage detection based on the pseudo-random identification principle. Firstly, the distribution of magnetic induction intensity, mean square error, and variation coefficient under various leakage depth conditions were characterized through the analysis of physical model experiments. Then, various leakage forms, high-resistance shielding layers, and leakage channel numbers were designed, so as to obtain the response characteristics of the detection results to the inclined channel, high-resistance shielding layer, and multiple leakage channels. Finally, the field test of Hongshiyan Dam in Yunnan Province was conducted to study the feasibility of this technology. The results show that under different burial depth conditions, the variation coefficients of maximum magnetic induction intensity vary within 2%. Along the inclined leakage channel, the magnetic induction intensity decreases slowly, and the ridge direction of the magnetic field contour map can be considered as the inclined leakage direction. The magnetic induction intensity is affected by the high-resistance shielding layer and has an error between 10% and 20%. The multiple leakage channels can be reflected by the concentrative distribution of abnormal zones in magnetic field contour maps. The leakage directions are observed in the field test, containing NW300°, SW265°, W215°, and NW305°, respectively.
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Key words:
- leakage identification /
- M sequence /
- magnetoelectric method /
- dam foundation leakage /
- soil bin test
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表 1 高精度磁电探测仪器性能指标
Table 1. Performance indexes of high-precision magnetoelectric detection instrument
项目 性能 发射功率/W 2000 发射电压/V 20 ~ 1200 发射电流/A 0.01~5.00 发射波形 M序列 位宽/ms 100~ 2000 阶数/阶 4~12 频带宽度/Hz 0.01~50.00 同步方式 GPS 同步 工作温度/℃ −20~70 磁力仪精度/T 1 × 10−9 最大测深/m 1000 表 2 模型试验方案设置
Table 2. Scheme setting of model test
试验组 渗漏通道电阻率/
(Ω·m)通道埋深/cm 通道数量/个 渗漏通道状态 屏蔽层 2.5 Ω•m土槽试验 2.5 5 1 平直 无 10 平直 20 平直 5 倾斜 高阻屏蔽层影响试验 2.5 10 1 平直 有 双渗漏土槽模型试验 2.5 10 2 平直,平行 无 平直,不平行 表 3 2.5 Ω•m模型试验均方差及变异系数
Table 3. Mean square error and variation coefficients in 2.5 Ω•m model test
渗漏埋深/cm S/( × 10−9 T) CV/% 5 2.78 0.41 10 3.16 0.94 20 3.32 1.93 表 4 渗漏磁感应强度最大值
Table 4. Maximum magnetic induction intensity of leakage
× 10−7 T 测线 测点 平行渗漏 非平行渗漏 1 5 2.38 2.19 9 2.36 2.07 2 17 2.30 2.11 21 2.23 2.04 3 29 2.28 2.13 33 2.39 1.98 4 41 2.35 2.06 45 2.26 1.99 表 5 磁感应强度极值大小及异常埋深
Table 5. Extreme value of magnetic induction intensity and abnormal burial depth
测点号 B/( × 10−9 T) 埋深/m 4 2.7 14.6 18 11.4 3.6 21 7.8 5.2 26 17.0 2.2 -
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