重金属污染土体的微细观结构及宏观力学特性研究

With the development of the industrialization and urbanization in China, many strata polluted by heavy mental have been encountered in city construction, which seriously affects the safety of the engineering structures. The influence mechanism of heavy metal on the properties of strata and micro/meso-structure and macroscopical mechanical properties of soil pollued by heavy soil are important issues to be solved.This project takes the heavy metal polluted soil as the object of study, on the basis of analysing corrosion of heavy metal to soil, firstly the experiment on micro/meso-structure and macroscopical mechanical properties of soil pollued by heavy soil will be conducted.Furthermore, the physical and mechanical model is established based on the micro/meso-structure of the pollued soil. And the meso mechanical method can be adopted to investigate the global mechanical properties of the soil polluted by heavy metal. Meanwhile, to establish constitutive model of contaminated soil considering the effects of the structural characteristic parameters, and to strive to simulate the macroscopic properties by researching the micro/meso structure of soil, and to reveal the damage mechanism of contaminated soil and realize the unity and combination of the analysis of micro/meso structure and the characteristics of the macro physical mechanics, as well as to accurately describe the physical and mechanical behaviors. The study results can effectively guide the urban engineering construction with heavy metal polluted soil underlying, and fill in the blank of research of geotechnical engineering characteristics of heavy metal polluted soil at home and abroad. At the same time, the results of this research can provide more scientific and more fundamental explanation about geotechnical engineering problems and will play a certain role in promoting the development of the soil mechanics theory.

随着我国工业化和城市化进程的加速，在城市建设中遇到了众多的重金属污染地层，这些地层将严重影响工程质量和安全，重金属对土层性质的侵蚀机理及土性变异前后的微细宏观力学特性是当前亟待解决的重要课题。本项目以重金属污染土体为研究对象，在分析重金属对土体侵蚀机理的基础上，首先开展污染土体微细观结构及宏观力学特性试验研究，其次从细观力学角度出发建立描述其微细观结构变化的力学模型，采用细观数值分析方法探讨污染土体的宏观力学特性，并考虑结构特征参数影响建立土-水-污染物相互作用的污染土本构模型，力求通过对土体微细观结构的研究获得对其宏观力学特性的精确描述，揭示污染土体的破坏机理，实现微细观结构分析与宏观力学特性的统一和结合。研究成果能够有效指导重金属污染地层的城市工程建设，填补国内外污染地层工程特性研究的空白，为岩土工程出现的环境问题给予更科学、更本质的解释，对土力学理论的发展也将起到极大的促进作用。

随着城市化和工业化进程的加速，工程建设中遇到了越来越多的重金属污染地层，严重影响工程质量和安全，随之带来的一系列工程问题已日益引起高度重视。侵蚀土体力学特性变异机理、特征及模型研究是污染场地再利用的核心关键问题之一，也是环境岩土工程领域亟待解决的重要课题。本项目通过人工配置污染土样，采用三联式柔性壁渗透仪及三轴仪开展了室内试验。主要研究工作和成果如下：.（1）渗液中单一组分 Cu 2+ 存在情况下，CuCl 2 溶液浓度保持恒定时，渗透液无论采用纯净水还是 CuCl 2 溶液，土体渗透系数均随着施加围压的增大而减小。施加围压相同而渗透液浓度不同的情况下，土体渗透系数随着 CuCl 2 溶液浓度的增加先急剧减小随后则逐渐增大。微观结构分析结果表明，CuCl 2 溶液作为渗透液时土体渗透系数与纯净水渗透存在差异的主要原因是重金属 Cu 2+ 改变了粘土的内部结构，影响了粘土的孔隙大小，从而造成了宏观渗透性的差异。.（2）渗液中多组分 Cu 2+ 和 Cr 3+ 、Cu 2+ 和 Mn 2+ 共同存在情况下，试验结果表明，对可溶性 Cu 2+ 和 Cr 3+ 、Cu 2+ 和 Mn 2+ 混合溶液侵蚀后的粘性土，其渗透性均随着掺入离子浓度比例的增大而逐渐增强。.（3）室内高岭土与 CuCl 2 溶液拌合制备的重塑土样固结不排水三轴剪切试验。结果表明，随着 Cu 2+ 浓度的增大，土样的轴向应力差不断降低，有效抗剪强度指标黏聚力和内摩擦角均降低，土体抗剪强度呈现弱化趋势。.（4）贵州黏土和北京粉质黏土分别与不同浓度 CuCl 2 溶液拌合并击实制备重塑土样，三轴试验结果表明随着侵入 Cu 2+ 浓度的增大，试样轴向应力差、有效抗剪强度指标均呈现降低趋势。.（5）利用含硫材料与工业废渣和生物质材料组配形成新型稳定药剂，通过对比分析选用新型稳定化药剂 SR1 协同水泥固化稳定化重金属复合污染土壤。结果表明药剂.的最优配比为 PC 掺量 8%，SR1 掺量 2.5%。.（6）28 天最优配比下固化土体无侧限抗压强度比未固化复合污染土壤强度对应值高 9.6 倍，达到 1080kPa；随着水泥掺量增加，固化体的有效粘聚力及有效内摩擦角均不断增大。加入稳定剂 SR1 使固化体渗透系数增大，但随着水泥掺量增加，渗透系数急剧降低。