污染土工程性质变异过程的电化学响应及其腐蚀性评价研究

Contaminated soil can be considered as a porous medium and special electrochemical system since the pore water of the soil could behave as electrolyte. In this study, the equations for electrochemical impedance characteristics, including Nyquist diagrams and Bode chart, of contaminated soils was obtained by using soil mechanics, chemical, electrochemical and microscopic analysis. The analysis is implemented in light of the relationship between mineral composition, microstructure, macro-performance and electrochemical characteristics of contaminated soil. The parameters for physical, mechanical and electrochemical properties were then obtained based on the EIS characteristic. By theoretical EIS analysis, the relationship between electrochemical properties and soil properties was determined. As a result, the equivalent circuit model and corrosion evaluation system for the contaminated soil were established, which can evaluate the soil contaminations and provide advices on electric double layer, electrode material, solid electrolyte and corrosion protections of metallic materials embedded in the soils. The results show that the EIS method is effective to evaluate the corrosions of contaminated soil by varying the soil parameters (moisture, porosity etc.) and simulating environmental influences (the type and content of contaminated media etc.). The results will broaden the theoretical foundation of soil mechanics and promote the applications of EIS method in geotechnical engineering.

污染土体可视为一种多孔介质体系，由于污染土体的孔隙液具有电解质的作用，可把污染土看成一个特殊的电化学体系，因此采用电化学阻抗谱法研究污染土的物理力学参数和外部环境因素对其腐蚀性的影响具有可行性。本项目通过土力学、化学、电化学及微观分析相结合的试验手段，以污染土矿物成分-微观结构-宏观性能-电化学特性四者之间的相互关系为主线，获取不同类型、不同湿度及不同污染源污染土的物理、力学及电化学参数，模拟试验得到的阻抗函数方程，应用电化学阻抗谱理论解析污染土的电解质电阻、电荷传递电阻、双电层电容和扩散阻抗系数与矿物成份、土体湿度、微观结构、孔隙分布及强度的关系规律；建立污染土电化学体系的等效电路模型和工程性质的评价体系，且该体系能够综合反映污染土的腐蚀过程动力学、双电层、电极材料、固体电解质以及腐蚀防护等内容。研究成果将进一步深化传统土力学理论，扩展了电化学方法在岩土工程中的应用范围。

污染土/重金属污染土作为一种特殊的电化学体系，应用电化学阻抗谱(EIS)法研究污染土的工程及物理化学性质具有一定的理论基础。本项目着重研究污染土工程性质变异过程的电化学响应。主要研究结果如下：（1）深化电化学原理及EIS技术在污染土中的关键理论，结合室内、现场试验结果，初步建立并完善了污染土EIS理论。（2）通过试验研究了典型砂土盐渍土和高岭土的EIS特征，建立了两种污染土体的等效电路模型，揭示了污染土的电化学腐蚀机理。（3）针对项目拟解决的关键技术问题，系统分析了污染土的电化学腐蚀行为，研发了一种土壤-钢材电化学腐蚀体系的测试装置。（4）初步探究了基于EIS理论及技术的重金属污染土固化效果，探讨了各因素对污染土物理力学及电化学性质的影响，进一步验证了EIS在污染土腐蚀性评价过程中的适用性。（5）通过试验研究了氯化钠污染粉土受毛细作用下的电化学腐蚀行为，掌握了盐渍土的物理化学性质与电化学性质之间的规律，建立了盐渍土在毛细作用下的等效电路模型，初步揭示了盐渍土中盐分迁移规律及其腐蚀机理。上述成果，可为应用EIS法研究污染土工程性质的可行性提供理论支撑，为丰富、拓展EIS法在环境岩土工程领域应用奠定理论基础和技术支持，技术成熟后可以了解岩土工程的变形破坏前兆，为判断工程的稳定性服务。