可降解土体BCHM耦合模型研究

发布时间：2018-07-10 20:03

本文选题：可降解土体 + 生化降解　；参考：《浙江大学》2015年硕士论文

【摘要】：可降解土体是指土体中的固相颗粒会在外部环境作用下会出现质量损失、颗粒破碎的现象,引起孔隙率和颗粒组构的变化,进而导致土体的土工特性及参数改变。常见的可降解土体有填埋场中高有机质含量的城市固废、土石坝中可侵蚀颗粒以及农田中石灰性土壤等。可降解土体的可降解特性导致其在多场耦合问题中变得尤为复杂。以填埋场为例,与普通土工构筑物中的多场耦合相比,填埋场还需要考虑生化降解对多场耦合的影响,主要体现在两方面：(1)由于固废中可降解有机质降解的影响,固废的土工特性会随着降解程度不同而变化；(2)由于降解产生的水、气、液相溶质等物质也会作为源相参加到水气运移和溶质迁移等运动中。基于此,本文在原有的多场耦合研究基础上,重点研究了多组分气体运移过程,以及降解过程对于模型参数的影响,主要内容和研究成果包括： (1)基于填埋场中气体涉及生化反应的情况,本文建立了考虑多组分气体运移的气相运移控制方程,并基于前人对多场耦合中其他过程的研究,给出了可降解土体的生化降解-骨架变形-水气运移-溶质迁移(BCHM)多场耦合模型,并界定了模型中涉及的土工特性及参数； (2)基于已有的颗粒级配曲线描述函数,本文从颗粒组构以及孔隙比出发,建立了固有渗透系数、相对液相/气相渗透系数、体相扩散/液相溶质扩散系数、努森扩散系数以及应力应变关系与颗粒级配曲线和孔隙比之间的关系,并对已有的土水特征曲线与颗粒级配曲线和孔隙比的关系进行了改进。通过改变颗粒级配曲线描述函数中的特征参数得到不同降解程度下的颗粒级配曲线,进而得到不同降解程度下的土工特性及参数。利用该预测模型,本文首先对不同降解模式下的各个土工参数的变化规律进行的分析。同时,以某填埋场为例,对不同龄期固废的土水特征曲线、固有渗透系数、相对液相/气相渗透系数进行了预测,并与试验实测结果比对,结果显示土水特征曲线、相对液相/气相渗透系数的预测结果与试验结果较为接近,固有渗透系数预测结果偏大于试验结果。 (3)基于可降解土体多场耦合模型和可降解土体土工特性及参数预测方法,建立了可降解土体多场耦合模型,并给出了求解方法。以典型中国城市固废为研究对象,采用可降解土体多场耦合模型,利用数值分析软件OpenGeoSys和Matlab,分别研究了降解速率、土工特性及参数随降解变化以及初始状态对填埋体的影响。计算结果表明,生化降解速率越快,沉降发展、气体逸出速率和渗滤液下渗速率越快；若不考虑降解过程对应力应变关系的影响,会导致预测的沉降量小,饱和度偏低；若不考虑降解对土水特征曲线的影响,会低估固废的降解程度；若不考虑降解过程对固有渗透系数的影响,会低估固废的饱和度。初始孔隙比越小,初始基质吸力越小,固废降解速率越快。 (4)为研究填埋场覆盖层气相污染物迁移规律,将本文多场耦合模型中的生化降解、骨架变形、孔隙水运移以及溶质迁移等过程忽略,退化至多组分气体运移模型。利用该模型分析了不同有效二元扩散系数、不同顶部边界下达到稳态时覆盖层气体组分分布。结果表明,稳态下各组分气体分布形式与有效气体二元扩散系数和顶部边界气体组分密切相关,对顶部边界气压大小不敏感。为研究考虑固结下填埋场衬垫系统液相污染物迁移规律,将本文多场耦合模型中的生化降解和孔隙气运移过程忽略,退化至骨架变形-孔隙水运移-溶质迁移耦合模型。利用该模型的分析了不同上部荷载、不同上部水头以及不同排水条件下污染物迁移规律。结果表明,液相污染物在衬垫系统中的迁移受到排水条件、顶部荷载、上部水头等因素的影响,上部水头越高、荷载越大,渗流路径与迁移路径一致时,污染物击穿衬垫的时间越短。
[Abstract]:The degrading soil is the mass loss of solid particles in the soil and the fragmentation of the particles in the soil, which causes the change of the porosity and the structure of the particles, which leads to the change of the soil properties and the parameters of the soil. The degradability of the particles and the calcareous soil in the farmland. The degradability of the degradable soil causes it to become particularly complex in the multi field coupling problem. Taking the landfill as an example, compared with the multi field coupling in the common geotextile structure, the landfill also needs to consider the effects of biochemical degradation on the multi field coupling, mainly in two aspects: (1) due to the solid waste. The effect of degradation of degradable organic matter will change with the degradation degree of the solid waste. (2) due to the degradation of water, gas, liquid phase solute and other substances will also participate in the movement of water gas and solute migration as the source phase. Based on this, this paper focuses on the study of multi component gas on the basis of the existing multi field coupling research. The main contents and achievements of the migration process and the effects of degradation process on the model parameters are as follows:
(1) based on the biochemical reaction of gas in the landfill, a gas migration control equation with multi component gas migration is established in this paper. Based on the previous studies of other processes in the multi field coupling, the multi field coupling model of biodegradability skeleton deformation, water gas migration and solute migration (BCHM), is given and the model is defined. The geotechnical characteristics and parameters involved in the model;
(2) based on the existing granular distribution curve description function, the intrinsic permeability coefficient, relative liquid / gas permeability coefficient, bulk diffusion / liquid phase solute diffusion coefficient, the relationship between the sudson diffusion coefficient and the relationship between the stress strain relationship and the grain gradation curve and the pore ratio are established. The relationship between the water characteristic curve and the grain gradation curve and the porosity ratio is improved. By changing the characteristic parameters of the particle grading curve, the particle gradation curves under different degradation degrees are obtained, and then the geotextile characteristics and parameters under different degradation degrees are obtained. At the same time, taking a landfill as an example, the soil water characteristic curve, intrinsic permeability coefficient, relative liquid / gas permeability coefficient of solid waste at different ages were predicted, and compared with the experimental results, the results showed the characteristic curve of soil water and the prediction result of relative liquid / gas permeability coefficient. Compared with the test results, the prediction results of intrinsic permeability coefficient are larger than the experimental results.
(3) based on the multi field coupling model of degradable soil and the geotechnical characteristics of degradable soil soil and parameter prediction method, the multi field coupling model of degradable soil is established and the solution method is given. Taking the typical Chinese urban solid waste as the research object, the multi field coupling model of degradable soil is adopted, and the numerical analysis software OpenGeoSys and Matlab are used to study respectively. The results show that the faster the biodegradation rate, the development of the sedimentation, the faster the gas escape rate and the leachate infiltration rate, and the smaller the predicted settlement and saturation, if the degradation process is not considered. If we do not consider the effect of degradation on the soil water characteristic curve, the degradation degree of solid waste will be underestimated. If the influence of the degradation process on the intrinsic permeability coefficient is not considered, the saturation of solid waste will be underestimated. The smaller the initial void ratio, the smaller the initial matrix suction, the faster the degradation rate of solid waste.
(4) in order to study the migration law of the gas phase pollutants in the cover layer of the landfill, the biochemical degradation, the skeleton deformation, the pore water migration and the solute migration in the multi field coupling model are ignored, and the gas migration model is degenerated to the multicomponent gas migration model. The different effective two element diffusion coefficients are analyzed with the model, and the steady state overlying under the different top boundary is reached. The distribution of gas components in the cover shows that the gas distribution of each component in the steady state is closely related to the two element diffusion coefficient of the effective gas and the gas component at the top boundary, and is insensitive to the pressure of the top boundary pressure. The process of solution and pore gas migration is neglected and degenerated to the skeleton deformation pore water transport coupling model. The model is used to analyze the different upper load, the different upper head and the transport of pollutants under different drainage conditions. The results show that the migration of liquid pollutants in the liner system is subjected to drainage conditions, top load, The influence of the upper head and other factors is that the higher the upper water head and the greater the load, the shorter the seepage path and the migration path.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU43

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