引用本文:申纪伟,毛海涛,王正成,闫 磊,唐 鑫.电极接触与间距对土壤电阻率测量的影响[J].土壤学报,2019,56(5):1247-1258.
SHEN Jiwei,MAO Haitao,WANG Zhengcheng,YAN Lei,TANG Xin.Influence of Electrode Contact and Distance on Soil Resistivity Measurement[J].Acta Pedologica Sinica,2019,56(5):1247-1258
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电极接触与间距对土壤电阻率测量的影响
申纪伟, 毛海涛, 王正成, 闫 磊, 唐 鑫
重庆三峡学院土木工程学院,重庆市三峡水库岸坡与工程结构灾变防控工程技术研究中心
摘要:
电阻率法在土壤测试的精确性方面存在较多不足,而电极是影响精度的重要原因,尤其是二极法。若能确定电极与土壤的接触程度及两电极间距离对测试结果的影响,将最大程度避免电极的干扰。基于米勒盒(Miller soil-box)测试模型,采用锌污染砂作为模拟土壤,以测试其交流电阻为例,进行系统的试验研究,建立了新的串联导电模型,分析了电极接触与间距对电阻的影响,又通过COMSOL软件仿真进行核准和补充,量化了测试误差。结果表明:试验研究和数值仿真能够相互验证和补充,说明建立的导电测试模型是正确的。导电模型划分了导电正常段与受电极影响的过渡段串联,过渡段长度随接触程度的增大而减小;过渡段中电流流网的变化产生了收缩电阻,随接触程度的增大而减弱,但二者不受电极间距的影响。过渡段长度与电流偏离程度又可借助仿真得出的径向电流密度精确表达,进而从数值上得出过渡段与正常段电阻率的偏差情况。误差分析中,测试所得的综合电阻率随着接触程度的增大和电极间距的增加而逐渐接近正常电阻率。上述研究可有效分析出因电极接触与间距而引起的测试偏差,得出正常电阻率,为测试中完善电极布置与提高测试精度提供合理建议。
关键词:  电阻率  精确性  COMSOL仿真  电极  电流密度
DOI:10.11766/trxb201810160413
分类号:
基金项目:重庆市教委科学技术研究项目(KJ1601017)、重庆市基础研究与前沿探索项目(cstc2018jcyjAX0673)和重庆市科委技术创新与应用示范项目(cstc2018jscx-msyb0517)资助
Influence of Electrode Contact and Distance on Soil Resistivity Measurement
SHEN Jiwei, MAO Haitao, WANG Zhengcheng, YAN Lei, TANG Xin
College of Civil Engineering, Chongqing Three Gorges University, Chongqing Engineering Research Center of Disaster Prevention & Control for Banks and Structures in Three Gorges Reservoir Area Chongqing
Abstract:
【Objective】The use of resistivity method in soil test has a number of shortcomings in accuracy and electrode is an important factor affecting accuracy of the test. In most tests, efforts are made to minimize contact and select appropriate electrode distance on the simple operational level. So accuracy of the test results is hard to correct and unify. Therefore, systematic analysis and quantification of these problems are required. If it is feasible to determine influences of contact and distance of the electrodes on test results, interference of the electrode can be avoided to the maximum extent, especially in pole-pole method. It is expected that this study may provide certain reasonable suggestions for electrode placement to minimize deviation of the test results in using the resistivity test device.【Method】In this paper, the soil-box resistivity test model was used to measure soil resistivity in zinc-contaminated sand used as simulated soil in the test. The test was designed to have three variables, i.e. soil water content, diameter of the electrode and distance between two electrodes for measurement of its AC resistance and resistivity (simply referred to as resistance and resistivity in the forthcoming paragraphs).Through the test with the indoor system and simulation of COMSOL physical field, influences of electrode contact degree and distance between electrodes on resistivity and its measurement were explored, a corresponding resistivity accuracy analysis model established, influences of contact and distance of electrodes on the test results discussed, and comparative analysis of errors and deviations of the test performed. 【Result】Results show that the experimental research and numerical simulation could verify and supplement each other, which indicates that the electric conductivity test model derived in this paper is correct. The electric conduction model could be divided into a normal section and transition sections at each end, connected in tandem. By means of the simulation, radial current density is used to reflect lengths of the transition sections and figured out the degree of current deviation. The change of current flow network produced shrinkage resistance in transition sections. Both shrinkage resistance and lengths of the transition sections decrease with the increase of contact degree, but are not affected by the distance between electrodes. After the length of the transition section was worked out, deviations of the resistivity of the transition and normal sections could be calculated numerically and accurately in line with the equation for calculation. Error analysis shows that the measured value of comprehensive resistivity gradually approaches that of normal resistivity with the expanding contact area and the extending distance of the electrodes. 【Conclusion】In summary, to keep electrodes in contact and properly apart is an effective way to reduce relative errors of the test to measure resistivity. In this study through numerical analysis, it is leant that deviation of the measurement of resistivity is caused by incomplete electrode contact and resistivity values of the normal sections can be worked out. All the findings in this study may serve as theoretical guidance and technical support for perfect electrodes arrangement and higher accuracy of the measurement of resistivity.
Key words:  Resistivity  Accuracy  COMSOL simulation  Electrode  Current density