论文总字数：29317字

摘 要

赤泥是制铝工业排出的污染性废渣，大量的赤泥不能充分有效的利用，只能依靠大面积的堆场堆放，既占用了大量土地，也对环境造成了严重的污染。在填埋场衬垫应用中，对于衬垫层的要求很高，一方面，需要衬垫有足够低的渗透系数，保证淋滤液不会渗出场地，造成对土体及水体的污染；另一方面，面对不均匀的应力分布，衬垫必须有足够的强度，以防止发生剪切破坏。因此，衬垫材料的选择对于堆场的稳定性具有重要意义。复合型的土工膜、土工织物等材料，具有较好的防渗性能，但是在应用中成本较高，对施工技术要求严格；击实粘土衬垫（CCL）成本相对较低，且在低离子浓度的环境中具有较低的渗透系数，但是赤泥堆场淋滤液含有大量的金属离子，PH值甚至高达13.0，在这样的环境中，CCL 的渗透系数会急剧上升，进而失效，达不到填埋场所规定的要求。因此，结合堆场往往位于北方荒芜的砂地的现实情况，采用击实砂-膨润土衬垫是阻滞赤泥堆场赤泥渗沥液污染土和地下水的最主要手段。

已有试验研究结果表明，各类聚合物改性膨润土在高浓度无机盐溶液作用下均表现出优于传统钠基膨润土的防渗性能，在高离子浓度的渗滤液环境中能够保持较低的渗透系数，更适合用于赤泥堆场高碱度环境中的应用。

本文通过无侧限抗压强度试验、API滤失仪改进滤失试验等系列试验，研究羧甲基纤维素钠（CMC）改性击实砂-膨润土的击实、强度和渗透特性，并对比传统砂-钠化钙基膨润土，得出了结论：（1）通过CMC改性膨润土较钠化钙基膨润土具有更好的膨胀和防渗性质；（2）CMC改性击实砂-膨润土的强度和防渗性能均明显优于砂-钠化改性钙基膨润土试验结果；（3）赤泥渗滤液作用下，采用CMC改性膨润土显著提升击实砂-膨润土防渗性能，渗透系数满足防渗要求（即k lt; 10-7 cm/s）。综述所述，CMC改性膨润土可用于赤泥堆场的底部防渗。

关键词：膨润土；聚合物改性；赤泥；渗透系数；化学相容性

Study on Strength and Chemical Compatibility of Compacted Sand-Bentonite Liner for Red Mud Disposal

Abstract

Red mud is the contaminated waste discharged from the aluminum industry. A large amount of red mud can not be fully and effectively utilized. It can only rely on a large area of dumping, taking up a large amount of land, and causing serious pollution to the environment. In landfill liner applications, the requirements for the liner layer are rigid. On the one hand, the liner needs to have sufficiently low permeability coefficient to ensure that the leachate does not leak out of the site and cause soil and water pollution; On the other hand, in the face of uneven stress distribution, the liner must have sufficient strength to prevent shear damage. Therefore, the choice of liner material is of great importance to the stability of the yard. Composite geomembrane, geotextiles and other materials have good anti-seepage performance, but the cost is high and strict construction technology requirements are needed in application. In contrast, the cost of compacted clay liner (CCL) is relatively low, and in the environment of low-ion concentration, CCL has a low permeability coefficient. But the leachate of the red mud dump contains a lot of metal ions, and the pH is even as high as 13.0. In such an environment, the CCL's permeability coefficient will rise sharply, failing to reach the standards of a landfill site. Therefore, combined with the fact that the dumping yard is often located in the deserted sands of the North, the use of compacted sand-bentonite liners is a most important means to retard the red mud leachate to contaminate soil and groundwater in the red mud dump.

Experimental results have shown that many types of polymer-modified bentonite have superior anti-permeability performance to conventional sodium bentonite under high concentration of inorganic salt solution, and can keep low permeability coefficient in high-ion concentration leachate environments, which is more suitable for the application in the high alkalinity environment of the red mud disposal.

In this paper, the compaction, strength and permeability of the mixture of sand and CMC-modified bentonite were investigated by carrying out a series of tests such as the unconfined compression strength test and improved API filtration test. Comparison was made with the mixture of sand and untreated-bentonite and the conclusion was drawn :

(1)CMC- modified bentonite has grater properties of expansion and seepage resistance than the untreated one; (2) The strength and permeability of compacted sand-CMC -modified bentonite are obviously better than the mixture of sand and sodium-treated calcium bentonite; (3) Under the environment of red mud leachate, CMC-modified bentonite can significantly improve the impervious performance of compacted sand -bentonite liner, and the permeability coefficient still meets the impervious requirements(k lt; 10^-7 cm/s). In summary, CMC-modified bentonite can be used to prevent seepage as the liner for red mud disposal.

Key words: bentonite; polymer treatment; red mud; permeability; chemical compatibility.

目 录

摘要 I

Abstract II

第一章 绪论 1

1.1 水平衬垫系统技术 1

1.2 聚合物改性膨润土在工程屏障中的应用研究 2

1.2.1 聚合物改性膨润土材料研究现状 3

1.2.2 改性工艺 4

1.2.3 改性机理 5

1.3 磷矿尾砂 6

1.4 赤泥渗沥液的环境污染 7

1.5 问题的提出 8

第二章 试验内容试验方法 9

2.1 试验材料 9

2.1.1 钠化膨润土 9

2.1.2 羧甲基纤维素钠改性膨润土 10

2.1.3 磷矿尾砂 10

2.1.4 污染液 12

2.2 试验过程 13

2.2.1 制备CMC改性膨润土 13

2.2.2 碟式液限仪测量液限试验 14

2.2.3 击实试验确定最大干密度 16

2.2.4 无侧限抗压强度实验 21

2.2.5 改进滤失试验测定渗透系数 24

2.2.6化学相容性试验 29

第三章 结论与展望 31

3.1 主要结论 31

3.2 不足与展望 32

致 谢 33

参考文献 34

第一章 绪论

1.1 水平衬垫系统技术

随着城市化进程的发展，我国固体废物的产量越来越大，其中包括了城市生活垃圾、工业固体废物，等等。面对我国大量的城市生活垃圾和废弃物堆场，填埋技术成为了我国处理这些固体废物的主要方式^[1]。

经过数十年的发展，垃圾填埋场从简单填埋发展到卫生填埋，一个现代化的卫生填埋场主要由5个系统组成：气体收集与控制系统、封顶系统、衬垫系统与渗滤液收集与排放系统、填埋气体与渗滤液处理系统等，分别起防、堵、排、治的功能。其中，水平衬垫系统的作用是将垃圾与周围环境隔开以免垃圾中的有害物质污染周围的土和地下水，是填埋技术最重要和最基本的防护系统^[2]。在卫生填埋场的整个系统中，为了避免垃圾填埋场中的渗滤液浸出污染土壤和地下水，进而引发一系列的环境岩土工程问题，选择好防渗衬垫材料是保证系统运行可靠性的关键一步。

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