合肥地区重金属污染膨胀土性能演变与改性土劣化机制

Heavy metal contaminants existed in the expansive soils may change its engineering properties. In order to improve expansive soil and solidification/stabilization of pollutants, it is necessary to fully understand the change law of the engineering properties of the contaminated expansive soil and the mechanism of strengthening and improving. Fistly, the project studies the engineering properties evolution of contaminated expansive soils. Based on the investigation using microscopic methods, distribution of grain size, specific surface area, mineral composition, etc. the change of engineering properties of contaminated expansive soil is recognized. Secondly, revealing the interaction between contaminants and expansive soils. Combining electrical resistivity, cation exchange capacity and Zeta-potential with microstructure analysis to establish the specified parameters referred to the evolution of soil engineering properties, which can generally illustrate the mechanism of engineering properties evolution. Thirdly, based on the study of improvement and solidification of contaminated expansive soil by using lime and industrial waste, the coupling mechanism of the improvement of expansive soil and the solidification / stabilization of pollutants was revealed. Finally, drying and wetting cycling test, leaching test with respect to the aggresive environment and carbonification test are conducted on the specimens to assess the long-term stability of stabilized contaminated expansive soil. Meanwhile, degradation mode will be proposed in both macroscopic and microscopic way, as well as the mechanism of degradation. In conclusion, this project will accelerate people to understand the evolution of engineering properties and solidified mechanism of contaminated expansive soil, and Promoting the development of contaminated site remediation and the theory of expansive soil improvement.

膨胀土受到重金属污染后，其工程性质如何演化、如何在改良膨胀土的同时有效固化/稳定污染物，是解决污染膨胀土地基难题的核心科学问题。本课题首先研究污染膨胀土的工程性质演化规律，从粒径分布、比表面积和矿物组成等微观角度，初步揭示膨胀土的工程性质变化机理；其次，分析污染物与膨胀土之间的相互作用，将电阻率、阳离子交换容量、zeta电位、比表面积、微结构分析等相结合，构建能全面反映土体工程性质变化的特征参数，全面揭示其工程性质变化机理；第三，研究基于石灰与工业废渣的污染膨胀土加固改良技术，揭示膨胀土改良与污染物固化/稳定的耦合作用机理；第四，通过加固改良污染膨胀土在干湿循环、化学物质渗淋、碳化等复杂环境因素耦合作用下的稳定性分析，提出由表及里、由浅入深的工程性质劣化模式，揭示其劣化机理。本课题将促进人们对污染膨胀土工程性质演化规律及加固改良机理的深入认识，推动污染场地修复与膨胀土改良理论的发展和完善。

随着城市发展，膨胀土地区污染企业搬迁带来了严重的场地污染问题。膨胀土是一种特殊的黏性土，受到重金属污染后，其工程性质如何演化、如何在改良膨胀土的同时，有效固化/稳定污染物，是解决污染膨胀土地基难题的核心科学问题。本项目阐明了重金属污染膨胀土工程性质演化规律、改良修复机理与改良膨胀土在复杂环境条件下的工程性质劣化机制，进而提出了重金属污染膨胀土地基改良修复方法。.（1）试验研究了不同类型、不同浓度重金属离子污染膨胀土的工程性质，阐明了其演化规律，并从粒径分布、比表面积和矿物组成等微观角度，揭示了膨胀土的工程性质变化机理。.（2）采用电阻率、阳离子交换容量、zeta电位、微结构分析等相结合方法，系统研究了污染物与膨胀土之间的相互作用，全面揭示了重金属污染土膨胀土工程性质变化微观作用机理。.（3）提出了基于石灰、碱渣、钢渣的重金属污染膨胀土固化技术，明晰了固化土的强度、胀缩性、化学稳定性等工程性能，获得了固化剂配比方案及改良方法，并通过矿物成分、微观结构、电阻率等分析，揭示了膨胀土改良与污染物固化/稳定的耦合作用机理。.（4）通过加固改良污染膨胀土在干湿循环、化学物质渗淋、碳化等复杂环境因素影响下的耐久性研究，阐明了加固改良污染膨胀土在复杂环境条件下的强度、化学与微结构稳定性，建立了由表及里、由浅入深的工程性质劣化模式，揭示了固化土工程性质劣化机制。.项目研究成果已发表学术论文22篇，其中SCI收录论文18篇，授权/申请发明专利5项（已授权3项），培养研究生6名。.本项目研究有利于促进对污染膨胀土工程性质演化规律及加固改良机理的深入认识，推动污染场地修复与膨胀土改良理论的发展和完善，推广应用前景广阔。