[目的]由于天然孔隙介质中存在物理化学非均质性,在这种复杂的非均质性含水层中,以往的现场试验数据显示溶质在非均质介质运移过程中无法用菲克扩散定律对流弥散方程(Advection-Dispersion Equation,ADE)来描述.本研究采用高密度电法证实溶质在非均质介质中非菲克运移.[方法]本研究采用石英砂、沸石两种不同基质构建双重介质物理模型(Models of Dual-Domain Mass Transfer,DDMT),采用高密度电法测定系统ERT21实时检测和采集数据,在实验室利用Nacl溶液开展示踪试验,利用阿尔奇定律分析溶质运移试验研究.[结果]试验结果浓度穿透曲线在后期发生"拖尾"现象;在沸石柱实验中,观察到流体电导率(σf)和体积电导率(σb)之间的滞后现象,这表明流体在不可动领域和可动领域之间的交换.而在沙子柱试验中,未观察到σf和σb之间的滞后现象,可以忽略质量传递行为;滞后现象的形状与大小由水动力学特征和基质属性控制,水动力学是影响拖尾时长的因素之一,渗透系数会影响溶质运移的过程.[结论]通过试验观察和地球物理数据分析,直接量化了实验室尺度下的异常质量传递行为,通过地球物理方法测量的导电率(σb)对于移动和不动领域都具有敏感性,从而提供了与标准采样方法相比的独特优势.
Experimental Study on Solute Transport in Dual Porosity Model Based on Archie's Law
[Purposes]Due to the physical and chemical heterogeneity in natural porous media,conven-tional field test data indicates that solute transport in such complex,heterogeneous aquifers cannot be de-scribed by the Advection-Dispersion Equation(ADE)of Fick diffusion.This study employs high-density electrical methods to confirm non-Fickian solute transport in heterogeneous media.[Methods]The study constructs dual-domain mass transfer models by two different substrates,quartz sand,and zeolite.The ERT21 system is employed for real-time monitoring and data collection through high-density electrical methods.Tracer experiments with sodium chloride solution are conducted in the laboratory,and the solute transport experiments are analyzed using Archie's law.[Findings]The experiment reveals a"tail"phe-nomenon in the concentration breakthrough curve during the later stages.In the zeolite column experi-ment,a lag between fluid electrical conductivity(σf)and bulk electrical conductivity(σb)is observed,indicating exchanges between immobile and mobile domains.In the sand column experiment,no lag be-tween σf and σb is observed,suggesting negligible mass transfer behavior.The shape and size of the lag phenomenon are controlled by hydrodynamic characteristics and matrix properties,with hydraulic char-acteristics being one of the factors affecting the duration of the tailing.Permeability influences the solute transport process.[Conclusions]Through experimental observation and geophysical data analysis,this study quantifies abnormal mass transfer behavior at the laboratory scale.The conductivity measured through geophysical methods(σb)is sensitive to both mobile and immobile domains,offering unique ad-vantages compared to standard sampling methods.
万方数据
维普
