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类型 应用研究 预答辩日期 2017-12-02
开始(开题)日期 2013-09-10 论文结束日期 2017-10-17
地点 岩土工程研究所二楼会议室 论文选题来源 国家社科规划、基金项目     论文字数 16.9 (万字)
题目 重金属作用下土-膨润土竖向隔离屏障化学相容性和防渗截污性能研究
主题词 竖向隔离,土-膨润土,重金属污染,化学相容性,防渗截污
摘要 我国存在大量重金属污染的城市工业污染场地,不仅污染环境,还严重制约城市可持续发展。土-膨润土竖向隔离屏障是具有代表性的一种原位竖向阻隔技术,可以有效控制地下水与土中污染物运移,是提高我国城市工业污染场地的综合处治和风险管控设计水平的重要需求。目前,土-膨润土竖向隔离屏障技术的关键技术问题在于:(1)我国商用膨润土以钠化改性钙基膨润土为主,工程性质与天然钠基膨润土存在明显差距,以此制备隔离屏障材料时,其膨润土设计掺量、施工和易性、压缩特性和防渗性能均尚不明确;(2)已有工程屏障材料化学相容性试验研究中普遍采用氯化钾和氯化钙溶液,重金属污染作用下土-膨润土竖向隔离屏障材料的化学相容性和防渗截污性能亟待明确。 基于此,论文以国家自然科学基金重点项目(No. 41330641)、国家自然科学基金项目(No. 51278100)、江苏省杰出青年基金项目(BK2012022)为依托,开展了土-膨润土竖向隔离屏障材料工程性质和典型重金属污染物作用下防渗截污性能的系统研究。主要研究内容和成果如下: (1)研究了膨润土浆液制备时膨润土的合理掺量,提出了基于膨润土液限的膨润土掺量预测方法;明确了隔离屏障材料满足施工和易性(塌落度)条件时的含水率分布规律,给出了基于隔离屏障材料液限和似液限的评价方法。 (2)明确了土-膨润土竖向隔离屏障材料压缩和固结特性。膨润土掺量和初始含水率是其控制因素。土-膨润土竖向隔离屏障材料的压缩指数与有效竖向应力为1 kPa时的孔隙比e1关系(Cc – e1关系)存在唯一性;其中,特征参数e1综合表征了初始含水率、膨润土掺量、膨润土品质和原位土土性对压缩指数的影响。提出了采用初始孔隙比和液限所对应孔隙比预测土-膨润土竖向隔离屏障材料压缩指数的方法。 (3)提出了满足防渗要求的钠化改性膨润土所制备土-膨润土竖向隔离屏障材料时的设计配比,揭示了膨润土掺量、膨润土品质、沸石掺量、天然黏土掺量、初始含水率和试验方法对隔离屏障渗透系数的影响规律。基于柯西-卡尔曼公式的预测方法对黏性土-膨润土竖向隔离屏障材料具有良好的适用性。提出了改进黏粒孔隙比以预测砂-膨润土和砂-黏性土-膨润土竖向隔离屏障材料渗透系数。 (4)阐述了重金属铅作用下黏性土-膨润土竖向隔离屏障材料压缩特性的变化规律,并明确了液限与压缩指数之间的内在联系。重金属铅对压缩指数的影响程度达12%~53%。污染作用下黏性土-膨润土竖向隔离屏障材料和其他土质工程屏障材料Cc – e1关系与未污染状态下土-膨润土竖向隔离屏障材料的试验结果一致。提出了基于扰动状态概念(DSC)的污染黏性土-膨润土竖向隔离屏障材料压缩模型。该模型采用单参数描述污染作用对压缩特性的影响。 (5)揭示了重金属铅、锌、铬作用下膨润土的渗透和膨胀特性。污染浓度超出10 mmol/L后膨润土渗透系数呈显著增大的趋势,且钠基膨润土渗透系数增幅明显高于钠化改性钙基膨润土试验结果。二价阳离子形式存在的重金属(例如铅、锌)与阴离子络合形态存在的六价铬对膨润土渗透系数的作用规律存在显著差异。自由膨胀指数良好地描述了无机盐溶液作用下膨润土的渗透系数变化规律。 (6)明确了重金属污染作用下土-膨润土竖向隔离屏障材料渗透系数的化学相容性。本文研究污染程度范围内,渗透系数的增幅不超过20倍,能够满足防渗要求(k < 10-9 m/s)。相同试验条件下,硝酸铅-硝酸锌溶液作用下砂-膨润土竖向隔离屏障材料渗透系数较氯化钙溶液作用下的试验结果高出2.9倍。分别就黏性土-膨润土和砂-膨润土、砂-黏性土-膨润土竖向隔离屏障材料提出了基于柯西-卡尔曼公式和改进黏粒孔隙比的渗透系数预测方法。 (7)提出了采用羧甲基纤维素钠(CMC)改性钠化改性膨润土。改性作用下CMC分子链插层于膨润土中蒙脱石黏土片层,有效提升了其膨胀和防渗性能。本文研究污染程度范围内,硝酸铅-硝酸锌、铬酸钾和氯化钙溶液作用下CMC改性膨润土渗透系数增幅小于1倍,远低于未改性膨润土试验结果。通过改进滤失试验测试了重金属作用下膨润土渗透系数,建立了污染前后滤失量与膨润土渗透系数的相关关系。 (8)研究了重金属铅、锌、铬运移通过砂-膨润土竖向隔离屏障的水动力弥散系数和阻滞因子。重金属铅、锌和铬在砂-膨润土竖向隔离屏障中的运移速率大小依次为:铬 > 锌 > 铅。通过van Genuchiten解分析了污染物运移参数、屏障厚度和污染物浓度阀值控制标准对击穿时间的作用规律,并给出了短期和中长期服役时间条件下的屏障厚度取值。在现有行业规范中屏障厚度设计方法基础上提出了1种基于van Genuchiten解的屏障厚度和服役年限简化计算方法。
英文题目 STUDY ON CHEMICAL COMPATIBILITY AND CONTAINMENT PERFORMANCE OF SOIL-BENTONITE CUTOFF WALL EXPOSED TO HEAVY METAL CONTAMINANTS
英文主题词 vertical barrier, soil-bentonite, heavy metal contamination, chemical compatibility, contaminant control
英文摘要 The heavy metal contaminated industrial sites not only pollute the environment but seriously restrict regional sustainable development and urbanization. Soil-bentonite cutoff wall is considered as an in-situ vertical engineered barrier used for controlling contaminant transport and enhancing risk control ability. Thus, it is a vital demand for China that contributes to raise capabilities of integrated treatment and risk management. After a review on testing results of engineering properties of soil-bentonite cutoff wall, it can be concluded that studies on the application of soil-bentonite cutoff wall still exist two main limitations as follows: (1) Bentonites available in China are generally sodium actived calcium-bentonites, whose swell potential and hydraulic conductivity are noticeably lower than natural sodium-bentonite used in all previous studies. However, the material composition, workability, compressibility and permeability of a soil-bentonite backfill created using sodium actived calcium-bentonite remain unknown. (2) Nontoxic salt solutions like potassium chloride and calcium chloride are popularly used in chemical compatibility testing of engineered barriers. None has been conducted on soil-bentonite backfills when exposed to heavy metal contaminants like lead, zinc and chromium. As a result, the main purpose of this study is to investigate the engineering properties and chemical compatibility of soil-bentonite backfills created using sodium actived calcium-bentonite, including clayey soil-bentonite, sand-bentonite and samd-natural clay- bentonite backfill. This study is financially supported by National Natural Science Foundation of China (Grant No. 41330641, 51278100), Natural Science Foundation of Jiangsu Province (BK2012022) and Scientific Research Foundation of Graduate School of SoutheastUniversity (Grant No. YBJJ1343). Main results are incorporated ad follows: (1) A series of workability testing is conducted to investigate the required bentonite content for bentonite-water slurry (BCS) and backfill water content range for construction (wB). Methods for predicting the workability parameters are proposed based on the correlations between workability parameters (i.e., BCS and wB) and physical index properties. (2) The compressibility and consolidation of the three types of soil-bentonite backfills are investigated via oedometer tests. Bentonite content and initial water content are two controlling factors that affect the compressibility. It is found that there exists a unique relationship between void ratio of σ’ = at 1 kPa and compression index, in which void ratio of σ’ = at 1 kPa reflects a compositive influence of initial water content, bentonite content, bentonite quality, and in-situ soil nature on the compression index of soil-bentonite backfills. According to this result, a method for predicting the compression index of various types of soil-bentonite backfills is proposed using initial water content and liquid limit. (3) Bentonite content required for achieving hydraulic conductivity limit regulatory (k < 10-9 m/s) is investigated. In addition, the influences of bentonite content, bentonite quality, zeolite content, natural clayey soil content, initial water content, and testing methods on the hydraulic conductivity are understood. Methods for predicting hydraulic conductivity of natural clayey soils in literature are adopted to predict the hydraulic conductivity of soil-bentonite backfills. An empirical method based on the framework of Kozeny-Carman equation is proposed to predict the hydraulic conductivity of the clayey soil-bentonite backfills. A new characteristic index, modified clay fraction void ratio, is proposed for predicting hydraulic conductivity of both sand-bentonite and sand/natural clay-bentonite backfills. The modified clay fraction void ratio reflects the influences of bentonite content, bentonite quality, and natural clayey soil content on the hydraulic conductivity. (4) Impact of presence of lead contamination in clayey soil-bentonite backfills on the compression behavior is investigated, which leads to a 12%~53% decrease in the compression index. The correlation between physical index properties and compression index (Cc) of both inorganic salts and organic compounds contaminated remolded clays, including clayey soil-bentonite backfills tested in this study, is understood. Liquid limit is an important index property that can reflect the chemical compatibility in terms of compressibility. Moreover, it is found that the unique relationship between the void ratio of σ’ at 1 kPa (e1) and compression index can be used for both inorganic salts and organic compounds contaminated remolded clays. An empirical equation is, therefore, proposed for predicting the compression index of clean, inorganic salts, and organic compounds contaminated remolded clays. In addition, the compression behaviour of inorganic salts and organic compounds contaminated remolded clays is also estimated via a Disturbed State Concept (DSC) model. A simplified form of the general model is proposed for inorganic salts and organic compounds contaminated remolded clays, in which one single parameter is used for describing the impacts of presence of contaminants in soil. (5) Impact of typical heavy metal contaminants on the permeability and swell potential of bentonites is investigated via modified fluid loss test and swell index test. A considerable increase in hydraulic conductivity of bentonites is found when the metal concentration increases to 10 mmol/L. Moreover, such trend is more noticeable in Na-bentonite compared with the results of Na activied Ca-bentonite. The different formations in metcal ions significantly affects the impact of metal concentration on hydraulic conductivity of bentonites. Metal cation obviously leads an increase in hydraulic conductivity. In contrast, metal exists in anionic complex, such as hexavalent chrome, could hardly change the hydraulic conductivity. In addition, it is found that swell index can well describe the influence of inorganc salt on the hydraulic conductivity of various bentonites. (6) The chemical compatibility of soil-bentonite backfills exposed to heavy metal contaminants, in terms of hydraulic conductivity, is understood. The increase in the hydraulic conductivity due to the presence of heavy metal contaminants with metal concentration upto 500 mmol/L is less than 20-times. The resulting hydraulic conductivity would underestimate the impact of heavy metal on the hydraulic conductivity of soil-bentonite backfills. The hydraulic conductivity of soil-bentonite backfills permeated with lead nitrate-zinc nitrate mixtures is 2.9-times higher than that permeated with calcium chloride for a given total metal concentration. Based on the methods for predicting the hydraulic conductivity of clean soil-bentonite backfills, empirical equations developed from the Kozeny-Carman equation and modified clay fraction void ratio are proposed for predicting the hydraulic conductivity of clayey soil-bentonite and sand-bentonite backfills when permeated with heavy metal solutions, respectively. (7) Carboxymethyle cellulose (CMC) treatment is applied to enhance the chemical compatibility of sodium actived calcium-bentonite in terms of swell potential and hydraulic conductivity when subjected to heavy metal contaminants. The mechanism of CMC treatment is understood via Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction analysis. Several series of index property tests, modi?ed fluid loss tests and flexible-wall hydraulic conductivity tests are conducted using CMC treated Ca-bentonite with deionized water, heavy metals-laden water, and actual landfill leachate. The result indicates that CMC treated Ca-bentonite yields a relatively lower hydraulic conductivity compared to the untreated Ca-bentonite under a given contamination condition. In addition, the modified fluid loss test can be considered as a quick method for estimating the chemical compatibility of bentonites in terms of hydraulic conductivity. (8) The transport parameters, hydrodynamic dispersion coefficient and retardation factor of heavy metal contaminants during their transport through soil-bentonite backfill are estimated. The order of the mobility of lead, zinc, and hexavalent chromium is: Cr(VI) > Zn > Pb. Factor analysis is conducted to understand the influences of transport parameters, wall thickness, and concentration criterion for breakthrough time on the breakthrough time according to van Genuchten’s analytic solution. Based on this, required wall thickness values for achieving either short-term or long-term service are given. In additon, a simplified method is developed based on the van Genuchten’s analytic solution for the calculation of the required wall thickness under different concentration criterion as well as service life for a given wall thickness.
学术讨论
主办单位时间地点报告人报告主题
东南大学 2012.11.29 南京 范日东 地下水曝气技术综述
东南大学 2013.11.25 南京 范日东 隔离屏障材料压缩特性试验研究
东南大学 2012.06.18 南京 范日东 隔离屏障材料吸附与沉降特性试验研究
东南大学 2012.04.10 南京 范日东 黏土与污染物相互作用
东南大学 2011.10.14 南京 范日东 半透膜效应综述
东南大学 2011.03.04 南京 范日东 竖向隔离墙综述
中国环境科学研究院 2015.10 北京 范日东 Workability, compressibility, hydraulic conductivity and chemical compatibility of soil-bentonite backfills for vertical cutoff walls
东南大学 2015.06.03 南京 范日东 Estimating the compression behaviour of metal-rich clays via a disturbed state concept (DSC) model
     
学术会议
会议名称时间地点本人报告本人报告题目
GeoChicago2016 2016.08.15 芝加哥 Evaluating Hydraulic Conductivity of Heavy Metal-Contaminated Bentonite Filter Cakes Using Modified Fluid Loss Test
中国土木工程学会第十二届全国土力学及岩土工程学术大会 2015.07.18 上海 土-膨润土竖向隔离墙中膨润土滤饼的化学相容性试验研究
7th International Congress on Environmental Geotechnics 2014.11.13 墨尔本 Workability, compressibility, hydraulic conductivity and chemical compatibility of soil-bentonite backfills for vertical cutoff walls
     
代表作
论文名称
受铅污染的土-膨润土竖向隔离墙材料的压缩及渗透特性试验研究
Engineering behavior and sedimentation behavior of lead contaminated soil-bentonite vertical cutoff
Compressibility and hydraulic conductivity of sand/clay-bentonite backfills
Compressibility and hydraulic conductivity of clayey soil mixed with calcium bentonite for slurry wa
添加沸石对黏性土-膨润土竖向隔离墙材料压缩和渗透特性的影响
Effects of addition of fine-grained zeolite on the compressibility and hydraulic conductivity of cla
Evaluation of the hydraulic conductivity of clayey soil mixed with calcium-bentonite using odeometer
钙基膨润系土竖向隔离墙材料压缩及渗透特性试验研究
Estimating the compression behaviour of metal-rich clays via a Disturbed State Concept (DSC) model
Modified fluid loss test to measure the hydraulic conductivity of heavy metal-contaminated bentonite
土-膨润土系竖向隔离墙的施工和易性分析
Analysis of the workability of soil-bentonite slurry-trench cutoff walls
Impacts of presence of lead contamination on settling behavior and microstructure of clayey soil - c
 
答辩委员会组成信息
姓名职称导师类别工作单位是否主席备注
施建勇 正高 教授 博导 河海大学
缪林昌 正高 教授 博导 东南大学
朱志铎 正高 教授 博导 东南大学
唐朝生 正高 教授 博导 南京大学
刘志彬 正高 副教授 博导 东南大学
      
答辩秘书信息
姓名职称工作单位备注
王菲 副高 副研究员 东南大学