大变形固结条件下污染物迁移规律模型试验研究

发布时间：2018-10-31 20:30

【摘要】：我国对城市生活垃圾的处理方式主要是简易填埋,出于工程造价与技术难度等考虑,很多垃圾填埋场防渗垫层都是采用压实天然黏土作为防渗材料,因此如何防止垃圾渗滤液击穿黏土防渗层是垃圾填埋工程的关键所在。污染物迁移规律的研究是垃圾填埋场防渗设计的重点,对延长填埋场服役寿命,使环境免于破坏具有重要指导意义。本论文依托国家自然科学基金项目“饱和黏土大变形固结与污染物迁移多维耦合理论研究”,旨在研究饱和黏土大变形固结与污染物迁移耦合作用下污染物的运移扩散规律。首先基于相似定理,利用单因素分析、正交试验设计方法与敏感性分析方法,配制了符合模型试验条件的模型土;此外,对模型试验进行了自主设计,研究了土体在不同变形条件下非吸附性污染离子及吸附性污染离子的迁移规律;最后,基于COMSOL多场耦合数值软件,针对模型试验进行了数值模拟,实现了模型试验与数值模拟两者之间的相互验证。具体研究内容和结论如下:(1)以高岭石黏土、砂土、凡士林和硅油为基本材料,以砂土比1:2,骨胶比6:1,硅凡比1:1的质量比例关系成功配制出满足模型试验要求的模型土。该模型土具备模型试验要求的物理参数,同时也满足水理特性要求;(2)通过自主设计的模型试验,研究了土体变形条件对污染物迁移的影响。研究发现,对于非吸附性离子,土体固结变形(尤其是大变形)会对污染物迁移产生促进作用,大变形下的垃圾填埋场防渗能力弱于基于刚性介质与小变形假设的垃圾填埋场设计;(3)吸附性污染离子迁移深度较无吸附性离子浅,且吸附性离子的迁移虽然也会受到土体大变形固结的影响而加速自身迁移速率,但是相对于无吸附性离子来说,受土体变形影响已相对减小;(4)以模型试验实测数据为基础,拟合出衰减型污染物源浓度表达方程。这种污染源浓度处理方式更加贴近工程实际,所测出的污染物分布规律更加符合实际情况,在此基础上设计的模型试验更有研究价值;(5)以COMSOL Multiphysics软件为平台,以模型试验为基础,建立了黏土固结变形与污染物迁移耦合模型,并与模型试验所测得的污染物浓度分布等数据进行了对比分析。虽然试验数据与数值模拟计算数据存在一定差异,但是总体上对污染物迁移规律描述是相似的,基本实现了模型试验与数值模拟两者之间的相互验证。
[Abstract]:The main treatment of municipal solid waste in our country is simple landfill. In view of engineering cost and technical difficulty, many landfill sites use compacted natural clay as impervious material. Therefore, how to prevent landfill leachate from breaking through clay impervious layer is the key of landfill engineering. The study of pollutant migration law is the key point of landfill seepage control design. It is of great significance to prolong the service life of landfill site and avoid environmental damage. The purpose of this paper is to study the transport and diffusion law of saturated clay under the coupling action of large deformation consolidation and pollutant migration with the aid of the National Natural Science Foundation of China, "Multi-dimensional Coupling Theory Research on large deformation consolidation and Pollutant Migration of saturated Clay". Firstly, based on the similarity theorem, the model soil is prepared by using single factor analysis, orthogonal design method and sensitivity analysis method. In addition, the model tests were designed independently, and the migration laws of non-adsorptive contaminated ions and adsorptive contaminated ions in different deformation conditions were studied. Finally, based on the COMSOL multi-field coupling numerical software, the numerical simulation of the model test is carried out, and the mutual verification between the model test and the numerical simulation is realized. The specific research contents and conclusions are as follows: (1) with kaolinite clay, sand, vaseline and silicone oil as the basic materials, the ratio of sand to soil is 1: 2, and the ratio of bone to glue is 6: 1. The model soil which meets the requirements of model test has been successfully prepared according to the 1:1 mass ratio of silicon. The model soil has the physical parameters required by the model test and meets the requirements of the hydrological characteristics. (2) through the self-designed model test, the influence of the soil deformation conditions on the pollutant transport is studied. It has been found that, for non-adsorptive ions, consolidation deformation (especially large deformation) of soil can promote pollutant migration. The anti-seepage ability of landfill under large deformation is weaker than that of landfill design based on rigid medium and small deformation hypothesis. (3) the migration depth of adsorbed contaminated ions is lighter than that of non-adsorptive ions, and the migration of adsorptive ions will be accelerated by the large deformation and consolidation of soil, but compared with the non-adsorptive ions, The influence of soil deformation has been relatively reduced. (4) based on the measured data of model test, the expression equation of attenuated pollutant source concentration is fitted. The pollution source concentration treatment method is more close to the engineering practice, the measured pollutant distribution law is more in line with the actual situation, and the model test designed on this basis has more research value. (5) based on the COMSOL Multiphysics software and the model test, the coupling model of clay consolidation deformation and pollutant migration is established, and the data of pollutant concentration distribution measured by the model test are compared and analyzed. Although there are some differences between the experimental data and the numerical simulation data, the general description of the pollutant transport law is similar, which basically realizes the mutual verification between the model test and the numerical simulation.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X799.3

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