固化重金属污染土的工程性质与作用机理研究

发布时间：2018-07-05 19:29

本文选题：固化重金属污染土 + 强度　；参考：《合肥工业大学》2015年硕士论文

【摘要】：由于我国工业领域的快速发展,土壤重金属污染问题日益严重。因此开展重金属污染土的固化修复技术研究,并将其广泛应用于重金属污染场地的修复与再利用具有重要的意义。本文采用水泥、粉煤灰作为固化剂,通过系统的试验和深入的理论分析,研究固化重金属污染土的工程性质、淋滤特性,电阻率特性及微结构变化规律。得到的主要结论如下：(1)对比分析了养护龄期、固化剂类型及掺量和重金属类型及掺量对固化重金属污染土无侧限抗压强度和压缩指标的影响。结果表明：水泥／粉煤灰固化重金属污染土的无侧限抗压强度和压缩模量均随养护龄期的增大而增大,压缩系数随之减小；固化土体的无侧限抗压强度和压缩模量随着水泥掺量的增大而增大,压缩系数随之减小,随着粉煤灰掺量的增大土体的强度及压缩性变差；重金属离子浓度越高,固化效果越差。(2)对水泥／粉煤灰固化重金属污染土的三轴应力-应变特性进行了研究。得知固化重金属污染土的变形大体上可分为三个阶段：弹性变形阶段、塑性屈服阶段和破坏阶段。三种固化重金属污染土的破坏应力大小顺序为：PbCrZn;破坏应变大小顺序为：CrZnPb.水泥／粉煤灰固化锌污染土的破坏应力随Zn2+浓度的增大而减小；破坏应变则相反。水泥固化锌污染土的破坏应力比水泥+粉煤灰的破坏应力大,而破坏应变则相反。(3)通过TCLP试验对比分析了养护龄期、固化剂类型及掺量和重金属类型及掺量对固化重金属污染土淋滤特性的影响。结果表明：固化污染土的滤出液中重金属离子浓度随着养护龄期的增大而减小；对于水泥和水泥+粉煤灰固化铅和锌污染土,当重金属离子浓度小于5000mg/kg时滤出液重金属浓度均满足环境要求；水泥和水泥+粉煤灰固化铬污染土滤出液重金属浓度均满足环境要求；粉煤灰固化效果较差；水泥和粉煤灰对重金属离子包裹吸附作用的大小顺序为：CrZnPb.(4)对水泥／粉煤灰固化重金属污染土的平均电阻率、孔隙液电阻率及电阻率结构参数的变化规律进行了研究,并对固化污染土的平均电阻率与强度特性和淋滤特性之间的关系进行了分析。结果表明：不同固化剂固化污染土的电阻率大小为：水泥水泥+粉煤灰粉煤灰；固化土体的平均电阻率和孔隙液电阻率均随着养护龄期的增大而增大；平均结构因子和平均形状因子随养护龄期的增大而增大,各向异性系数相反；平均电阻率与强度及压缩性呈正相关,与滤出液中重金属离子浓度呈负相关。(5)对比分析了不同养护龄期和不同重金属及掺量下水泥和水泥+粉煤灰固化重金属污染土的微结构特征。结果表明：水泥／粉煤灰固化污染土中有大量水化产物生成,其孔隙数量及大小随着养护龄期的增大逐渐减小,结构逐渐变得致密；水泥+粉煤灰固化污染土中存在大量的微珠结构；随着固化污染土中的Zn2+浓度的增大,土体中的水化产物减少,孔隙数量增多,土体变得较为疏松。
[Abstract]:Because of the rapid development in the field of heavy metal pollution in China , the problem of heavy metal pollution in soils is becoming more and more serious . Therefore , it is of great significance to carry out the research on curing and repairing of heavy metal contaminated soil . The main conclusions are as follows : ( 1 ) The effect of curing age , type of curing agent and the type and content of heavy metals on the compressive strength and compression index of solidified heavy metal contaminated soil is studied .
The compressive strength and compressive modulus of the solidified soil mass increase with the increase of cement content , and the compressive coefficient decreases . As the content of fly ash increases , the strength and compressibility of soil are worse .
The higher the concentration of heavy metal ions , the worse the curing effect . ( 2 ) The three - axis stress - strain characteristic of the solidified heavy metal contaminated soil is studied . It is found that the damage stress of the solidified heavy metal contaminated soil can be divided into three stages : the elastic deformation stage , the plastic yield phase and the failure stage . The order of breaking stress of three kinds of solidified heavy metal polluted soil is :
The results show that the concentration of heavy metal ions in the filtrate of solidified polluted soil decreases with the increase of curing age .
For cement and cement + fly ash solidified lead and zinc polluted soil , when heavy metal ion concentration is less than 5000mg / kg , the heavy metal concentration of filtrate meets the environmental requirements ;
the heavy metal concentration of the cement and cement + fly ash solidified chromium polluted soil filter liquor meets the environmental requirements ;
the curing effect of the fly ash is poor ;
The order of the adsorption of heavy metal ions by cement and fly ash is as follows : CrZnPb . ( 4 ) The change law of the average resistivity , pore liquid resistivity and resistivity structure parameters of the heavy metal contaminated soil of cement / fly ash cured , and the relationship between the average resistivity and the strength characteristic and the leaching characteristic of the solidified polluted soil is analyzed . The results show that the resistivity of the solidified polluted soil of different curing agents is : cement cement + fly ash fly ash ;
The average resistivity of solidified soil and the resistivity of pore liquid increase with the increase of curing age ;
The average structure factor and the average shape factor increase with the increase of curing age , and the anisotropy coefficient is opposite ;
The average resistivity is positively correlated with the strength and compressibility , negatively correlated with the concentration of heavy metal ions in the filtrate .
There is a lot of microbead structure in cement + fly ash solidification polluted soil .
With the increase of Zn ~ ( 2 + ) concentration in solidified polluted soil , the hydration products in the soil decreased , the number of pores increased , and the soil became more loose .
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU41;X53

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