生活源污染质渗流-化学协同作用下土体性质结构研究

发布时间：2018-05-24 03:45

本文选题：生活源污染质 + 粉质黏土　；参考：《中国矿业大学》2017年硕士论文

【摘要】：生活污水和垃圾渗滤液在土体入渗的过程中,既存在物理渗流作用,又存在污染质与土体颗粒间的化学作用,对土体产生渗流、化学方面的侵蚀,导致土体的水理力学性质和结构发生重大变化。本文以粉质黏土为研究对象,选取对土体性质结构影响最为显著的CH_3COOH和Ca-CO_3为切入点,试验研究了粉质黏土的渗透性、抗剪强度、压缩性和微观结构随渗流压力、轴向压力、渗流深度以及污染质浓度的变化规律,并对生活源污染质渗流-化学协同作用影响粉质黏土水理力学性质和结构的规律与机理进行了阐释。研究表明:(1)生活源污染质不同降解阶段的主要有机和无机产物是CH_3COO~-和CO_3~(2-),并因此选定CH_3COOH和Ca-CO_3为本文研究的生活源污染质成分。(2)蒸馏水、CH_3COOH和Ca-CO_3污染液(Ca Cl_2与Na_2CO_3混合溶液)三组流体在粉质黏土渗流过程中,渗流压力和轴向压力对土体力学性质的作用效果相似,表现为渗流压力与粉质黏土的渗透性和压缩性正相关,与抗剪强度负相关,轴向压力与粉质黏土的渗透系数、压缩系数负相关,与抗剪强度正相关;就渗流深度而言,蒸馏水作用下土体的渗透性、抗剪强度和压缩性基本不随渗流深度而变化,CH_3COOH污染液作用下深度与渗透性负相关,与抗剪强度和压缩性正相关,Ca-CO_3污染液作用下深度与渗透性和压缩性负相关,与抗剪强度正相关;对于浓度而言,CH_3COOH污染液渗流下,CH_3COOH浓度与土体渗透性正相关,与抗剪强度和压缩性负相关,而Ca-CO_3污染液渗流下Ca-CO_3浓度与土体渗透性和压缩性负相关,与抗剪强度正相关。(3)渗流作用使粉质黏土的渗透性和压缩性提高,抗剪强度降低;CH_3COOH的化学作用使粉质黏土的渗透性提高,使抗剪强度和压缩性降低;Ca-CO_3的化学作用使粉质黏土的渗透性和压缩性降低,黏聚力增大而内摩擦角有所减小。CH_3COOH的化学作用对粉质黏土渗透性质、力学性质的影响效果强于Ca-CO_3。(4)生活源污染质的渗流-化学协同作用表现出空间分布的阶段性和影响工程地质性质参数的复杂性等特征。在渗流深度较低的阶段,生活源污染质对土体的作用主要体现为CH_3COOH的化学作用,使土体渗透性提高,抗剪强度和压缩性降低;在高渗流深度阶段,生活源污染质的作用主要表现为生活源污染质的降解物质与土体反应生成沉淀物质的化学作用,使土体渗透性和压缩性降低,黏聚力提高。Ca-CO_3污染液对粉质黏土黏聚力和内摩擦角的渗流-化学协同作用规律并不一致,体现了生活源污染质渗流-化学协同作用的复杂性。(5)渗流作用和CH_3COOH的化学作用增强了土体的孔隙发育程度,使土体孔隙总面积、孔隙平均面积、孔隙度和孔隙比等参数显著增大,分形维数减小。在渗流深度较低的范围内,CH_3COOH的化学作用对土体微观结构起主导作用,并随着深度的增加逐渐减弱。Ca-CO_3污染液对粉质黏土微观结构的渗流-化学协同作用规律与CH_3COOH相反。(6)渗流作用影响土体性质和结构的机制是通过渗透压力改变土体孔隙分布,CH_3COOH则是通过改变颗粒吸附电荷平衡、溶解、腐蚀大量黏土矿物影响土体性质结构,而Ca-CO_3是通过生成碳酸盐沉淀填充孔隙对土体性质结构产生影响。生活源污染质渗流-化学协同作用在深度上的作用机制是,低深度阶段,污染液渗流力改变土体孔径和孔隙的作用较大,同时CH_3COOH对土体的化学作用也显现。随着污染液渗流深度的增大,CH_3COOH的降解和发酵产物发挥作用,表现为Ca-CO_3对土体的化学作用。
[Abstract]:In the process of soil infiltration of domestic sewage and landfill leachate, there are both physical percolation and chemical action between pollutants and soil particles. The seepage of soil and chemical erosion have resulted in great changes in the mechanical properties and structure of soil. This paper takes the clay as the research object and selects the soil properties. CH_3COOH and Ca-CO_3, which have the most significant influence on the quality structure, have been tested to study the permeability, shear strength, compressibility and microstructure of the clay with percolation pressure, axial pressure, percolation depth and concentration of contaminants, and the effect of chemical synergism on the pollution of living sources and the effect of chemical synergism on the mechanical properties of silty clay. The law and mechanism of the quality and structure were explained. The study showed that: (1) the main organic and inorganic products of different degradation stages of the source of life pollution were CH_3COO~- and CO_3~ (2-), and CH_3COOH and Ca-CO_3 were selected as the sources of pollution in this paper. (2) distilled water, CH_3COOH and Ca-CO_3 contamination solution (mixed solution of Ca Cl_2 and Na_2CO_3) During the percolation process of the three groups of fluid, the effect of the seepage pressure and the axial pressure on the mechanical properties of the soil is similar, which shows that the seepage pressure is positively related to the permeability and compressibility of the silty clay, and is negatively correlated with the shear strength. The axial pressure is negatively correlated with the permeability coefficient of the silty clay and the compression coefficient, and is positive with the shear strength. As far as seepage depth is concerned, the permeability, shear strength and compressibility of soil under the action of distilled water do not change with the depth of seepage. The depth of CH_3COOH contamination is negatively correlated with permeability, and is positively related to shear strength and compressibility. The depth of Ca-CO_3 contamination is negatively correlated with permeability and compressibility, and positive phase of shear strength. For the concentration of CH_3COOH, the concentration of CH_3COOH is positively related to the permeability of soil, which is negatively related to the shear strength and compressibility, while the Ca-CO_3 concentration under the percolation of Ca-CO_3 is negatively related to the permeability and compressibility of the soil, and is positively related to the shear strength. (3) the permeability and compressibility of the silt clay are improved by percolation. The shear strength is reduced, and the chemical action of CH_3COOH makes the permeability and compressibility of the silty clay lower, the chemical action of Ca-CO_3 reduces the permeability and compressibility of the silty clay, the cohesiveness increases and the internal friction angle decreases with the.CH_3COOH, which has a strong effect on the mechanical properties of the silty clay. The percolation chemical synergistic effect of the Ca-CO_3. (4) source of pollution shows the characteristics of the spatial distribution and the complexity of the engineering geological parameters. In the stage of low seepage depth, the effect of the source of pollution on the soil is mainly reflected by the chemical action of CH_3COOH, which makes the soil permeability, shear strength and pressure. In the stage of high seepage depth, the effect of pollution in the source of life is mainly the chemical action of the degradation substance of the source of pollution and the reaction of the soil to the sediment, which reduces the permeability and compressibility of the soil, and the cohesiveness enhances the percolation chemical synergy of the cohescohesion and the internal friction angle of the.Ca-CO_3 contamination solution to the silt clay. The regularity is not consistent, which embodies the complexity of the chemical synergism of the pollution of the source of life. (5) the pore development of the soil is enhanced by the seepage action and the chemical action of CH_3COOH, which makes the total pore area, the pore average area, the porosity and the porosity ratio significantly increase, the fractal dimension decreases and the range of the seepage depth is low. The chemical action of CH_3COOH plays a leading role in the microstructure of soil. With the increase of depth, the seepage chemical synergistic action of.Ca-CO_3 contaminant on the microstructure of silty clay is opposite to that of CH_3COOH. (6) the mechanism of the effect of seepage effect on soil properties and structure is to change the pore distribution of soil through the permeation pressure, CH_3CO OH is by changing particles to adsorb charge balance, dissolving and corroding a large number of clay minerals to influence the soil properties, while Ca-CO_3 is an effect on the structure of soil by the formation of pores filled with carbonate precipitation. The effect of the pore size and pore size of the soil is larger, and the chemical effect of CH_3COOH on the soil is also apparent. With the increase of the seepage depth of the polluted liquid, the degradation of CH_3COOH and the fermentation product play a role, which is the chemical effect of Ca-CO_3 on the soil.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU43

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