饱和黏土一维压缩对离子扩散运移特性影响试验研究

论文总字数：62485字

摘 要

污染物在土体中的运移机制包括对流、扩散、弥散、吸附、降解和化学反应等。实际工程中，自重及上部荷载易使土体产生固结变形。一方面，污染土的固结变形将引起其中污染物溶液的对流；另一方面，随着固结变形的发展，土的孔隙比、渗透与固结系数亦随之改变，污染物在土体中的水动力弥散系数亦随之改变，进而影响污染物在其中的运移特性。

本文通过一维压缩试验，得到压缩变形过程不同孔隙比下的试样，然后对相应的试样进行纯扩散试验，获取不同孔隙比下离子扩散引起的水溶液浓度和电导率变化规律差异性；此外，尝试通过简化模型，利用POLLUTE获取试样扩散系数，进而建立孔隙比与扩散系数间量化经验关系；最后，通过压汞试验获得量化的孔径尺度及分布情况量化指标，为离子在黏土孔隙中的扩散运移性能提供参考。总结全文，得出的主要研究成果如下:

（1）内扩散试验过程中，由于烧杯溶液和试样孔隙溶液浓度梯度的存在，向土体当中运移。当烧杯溶液和试样孔隙溶液浓度相等时，扩散作用到达平衡状态。内外溶液浓度梯度越大，扩散速度越快。

（2）黏土孔隙比的改变会改变溶质在其中的运移特性，孔隙比越小的试样，扩散平衡时，烧杯中浓度越高，电导率越高，即离子向土体当中的扩散量越少。

（3）通过POLLUTE推得在试样中的扩散系数为0.004-0.008和其他学者得到的在土体中扩散系数为一个数量级。

（4）通过压汞试验得到，扩散所用高岭土试样微观孔隙以颗粒间孔隙为主。孔隙比为0.75、0.65、0.57、0.53的试样微孔部分以0.950、0.612、0.433、0.284为主。

关键词: 固结变形，污染物运移，POLLUTEv7，内扩散试验，有效扩散系数，压汞试验

Abstract

The mechanisms of contaminant transport in soil include advection, diffusion, dispersion, sorption, biological degradation, chemical reaction and so on. In engineering practice, deformation of consolidation will take place due to self-weight of soils and applied load. On the one hand，consolidation of contaminated soils will lead to advection of the contaminated pore fluid. On the other hand, the void ratio and consolidation coefficient of the soil as well as the hydrodynamic dispersion coefficient of the contaminant will also be changed with the development of deformation, which will comprehensively influence the transport behavior of the contaminants.

In this paper, one-dimensional compression experiments are conducted to make kaolinite samples with different porosity, which then will be used as porous medium in the coming inner-diffusion tests. Moreover, POLLUTEv7 software is used to estimate the diffusion coefficient of chloride, which can help build the empirical relationship between porosity with diffusion coefficient. Finally, pore scale for kaolinite samples are obtained using mercury intrusion(MIP) test, which also can support to the discussion of ions diffusion in the pore of clay. The following conclusions were drawn from these tests:

(1)In the inner-diffusion tests, because of the concentration gradient between samples and surround solution, diffuses from a region of greater to one of less concentration. When the concentration between these two regions is equal, the diffusion will be terminated. Higher the concentrate gradient is, faster the diffusion will be.

(2) Change of porosity of the kaolinite may change the transport character of solute in the kaolinite. Samples with smaller pore size, higher concentration and electrical conductivity may measure from outer solution, which means fewer diffuse into kaolinite.

(3) The effective diffusion coefficients of chloride estimated from POLLUTE software are found to vary from 0.004 to 0.008, a similar range to that observed by other researchers.

(4) MIP results indicate that pore structure of the kaolinite samples mainly consists of interparticle pores whose entrance pore diameter varies between 0.005-1.5. Corresponding peak values of such kind of micropores for samples with porosity of 0.75、0.65、0.57、0.53 are 0.950、0.612、0.433、0.284，respectively.

KEY WORDS: Consolidation, Contaminant transport, POLLUTEv7, Inner-diffusion test, Effective diffusion coefficient, Mercury intrusion test

目录

摘 要 I

Abstract II

第一章 绪论 1

1.1 研究背景和研究意义 1

1.2 研究现状分析 1

1.2.1理论研究进展 1

1.2.2 试验研究进展 3

1.3 工程应用 7

1.4本文主要研究内容 7

1.5 研究技术路线与结构框架图 8

第二章 饱和压缩高岭土的氯离子内扩散试验方案 9

2.1 概述 9

2.2 试验材料 9

2.2.1 高岭土 9

2.2.2 氯化钾 10

2.3 试验内容及方法 10

2.3.1 一维压缩试验 10

2.3.2 离子运移试验 12

2.3.3 微观性质试验 14

第三章 内扩散试验过程溶液池氯离子浓度变化 15

3.1 概述 15

3.2 离子运移试验数据 15

3.2.1 电导率值与氯离子浓度关系 15

3.2.2 氯离子浓度数据 16

3.2.3 电导率值数据 17

3.3 本章小结 18

第四章 基于内扩散试验结果的有效扩散系数分析 19

4.1 概述 19

4.2 有效扩散系数基本理论 19

4.3 基于有限溶质一维扩散理论的内扩散试验简化分析 20

4.3.1有限溶质一维扩散理论模型 20

4.3.2 内扩散试验简化计算模型及参数取值 21

4.3.3 POLLUTE计算步骤详述 22

4.3.4 POLLUTE计算结果 25

4.4 理论计算与试验结果对比分析 25

4.4.1 POLLUTE拟合曲线与试验结果比较 25

4.4.2 试验规律偏差讨论 28

4.5 本章小结 29

第五章 微观机理研究 30

5.1 概述 30

5.2 压汞试验（MIP）原理 30

5.3 压汞试验结果与分析 31

5.4 本章小结 33

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