自然电位法实时监测地下流体运移实验研究

Lab-based experiment on real-time monitoring of underground fluid migration by self-potential measurement

查清地下流体运移的规模和渗透路径对工程渗漏检测以及水文地质调查具有重要意义.流体流动产生的动电效应会引发电荷的自然极化,通过定性或定量解释自然电位信号可表征地下水流的运移情况.本研究基于三维多通道自然电位观测系统搭建了室内沙箱实验平台,通过沙箱进水和排水试验,实时监测了非饱和-饱和以及饱和-非饱和过程的自然电位信号.实验结果表明自然电位偶极性分布特征与流体运移方向有着显著的相关性,符合动电效应理论.采用最小二乘正则化梯度算法反演实验测量数据,获得流动电流源密度并解释沙箱内部水流分布.此外还对野外堤坝渗流过程的自然电位数据进行类似的定量解释,反演的流动电流源所构建的水流指向与现场观测一致.本文从理论、方法、室内实验以及野外实测数据处理等多个角度论证了自然电位法在渗流监测中的效用,表明自然电位法是一种极具潜力的地下流体运移探测工具.

Examining the scale and pathways of underground fluid migration holds significant importance in engineering leakage detection and hydrogeological investigations.As the electrokinetic effect resulting from subsurface fluid flow can induce natural charge polarization,the qualitative or quantitative interpretation of self-potential(SP)data aids in characterizing the movement of underground water flow.In this study,we constructed an indoor sandbox experiment platform with a 3D multi-channel SP measurement system.Real-time 3D SP data was collected during the imbibition process of dry quartz sand and the drainage process of saturated sand,covering the transition from unsaturated to saturated and saturated to unsaturated conditions.The experimental results demonstrate a significant correlation between the polarity characteristics of the measured SP signals and the fluid direction,consistent with the theory of the electrokinetic effect.To quantitatively interpret the experimental measured SP data,we employed the least square regularized gradient inversion algorithm,enabling the determination of streaming current density and demonstrations of water flow distribution within the tank.In addition,we conducted a similar quantitative interpretation of field SP data obtained from seepage detection in an earth-filled dam,and the recovered SP current density and fluid direction are consistent with field observations.This paper showcases the effectiveness of the SP method in monitoring seepage by comprehensively addressing the aspects of theory,method,lab-based experiments,and field data processing,highlighting the applicability of SP surveys in detecting subsurface fluid migration.