磷污染红土的宏微观特性研究

发布时间：2018-08-12 08:32

【摘要】：以云南红土为研究对象,选择六偏磷酸钠为污染源,通过磷污染红土的土柱迁移试验,采用相对质量、颗粒组成、界限含水、矿化、离子浓度试验、微结构等试验方法,探讨了迁移条件下磷污染红土的宏微观特性；考虑六偏磷酸钠浓度和干密度的影响,采用击实、直剪、固结、渗透、微结构等试验方法,研究了受力件下磷污染红土的宏微观特性；结合磷与红土间的相互作用,阐明了磷土作用机理及其对宏微观特性的影响,揭示了磷污染红土的宏微观响应关系,对于有效防治污染红土中磷的迁移扩散、磷污染红土地区的用土安全提供理论依据。迁移条件下磷污染红土的宏观特性：磷污染红土相对质量、黏粒含量大于素红土,随土柱位置深度增加,磷污染红土的相对质量、黏粒含量减小,粉粒含量增加。液限、塑限和塑性指数土柱中上部处存在最小值,逐渐接近素红土。迁移条件下磷污染红土的物质组成特性：磷污染红土新生成不稳定的β-钠铁矿,对结晶较好的三水铝石、赤铁矿和锐钛矿的变化十分显著,红土中磷的含量在中上部处出现最大值,土柱表层氧化亚铁的含量最大；浸泡液的铁铝离子浓度随迁移时间延长而增大,渗流液中存在痕量的铁铝离子。迁移条件下磷污染红土的微结构特性：随土柱位置深度增加,磷污染红土微结构图像由上部致密的鳞片状单元向中部松散的蜂窝状进而向下部紧密的蜂凝状单元的变化,对应孔隙比在中上部处存在最大值；磷污染红土表面较为富集的元素为铁铝元素,红土的胶结堆聚体以包膜的形式包裹于颗粒基本单元外表面；磷污染红土颗粒面积减小、孔隙面积增加、颗粒的定向度和分维数先减小出现极值后增大。受力条件下磷污染红土的宏观物理力学特性：随磷浓度增加,磷污染红土的相对质量、黏粒含量增大,粉粒含量减小；界限含水率减小；最大干密度增大,最优含水率减小,存在最优浸润时间；红土的黏聚力降低,内摩擦角减小；压缩性增大；渗透性降低。受力条件下磷污染红土的微结构特性：随磷浓度增加,微结构单元体本身的胶结程度较高,单元间的联结程度较低,磷污染红土孔隙间、片状黏土矿物表面形成细小颗粒堆积物,形成新形式的红土结构体,磷污染红土的胶结堆聚体仍然以包膜的形式包裹于颗粒基本单元外表面,受力后磷污染红土微结构参数优于受力前的参数,磷污染红土力学性能变化是磷污染红土微结构弱化所致。磷与红土间的作用机理及其对宏微观特性的影响：磷污染对红土的作用机理及其对宏微观特性的影响可以从磷与红土间所存在的水解、吸附络合、还原氧化、成盐和溶解五个作用来解释,其综合作用的结果改变了磷污染红土的宏微观特性。
[Abstract]:Taking Yunnan laterite as the research object, the macroscopic and microscopic characteristics of phosphorus-contaminated laterite under the condition of migration were studied by the soil column migration test of phosphorus-contaminated laterite. The relative mass, particle composition, limiting water content, mineralization, ion concentration test and microstructure test were used to study the macroscopic and microscopic characteristics of phosphorus-contaminated laterite. The macro and micro characteristics of laterite contaminated by phosphorus were studied by compaction, direct shear, consolidation, infiltration, microstructure and other test methods. The interaction between phosphorus and laterite was combined to clarify the mechanism of action of phosphorus and its influence on macro and micro characteristics, and to reveal the macro and micro response relationship of phosphorus contaminated laterite. Macroscopic characteristics of phosphorus-contaminated laterite: the relative quality of phosphorus-contaminated laterite, clay content is greater than that of plain laterite. With the depth of soil column increasing, the relative quality of phosphorus-contaminated laterite, clay content decreases, and silt content increases. The material composition characteristics of phosphorus-contaminated laterite are as follows: the phosphorus-contaminated laterite is newly formed into unstable beta-sodalite, and the content of phosphorus in the laterite is the highest at the middle and upper part of the laterite. The content of iron oxide in the surface layer of the soil column is the highest at high value; the concentration of iron and aluminum ions in the soaking solution increases with the extension of migration time, and there are trace amounts of iron and aluminum ions in the percolating solution. Loose honeycomb-like structure in the upper part of the laterite, and then compact bee-like structure in the lower part of the laterite, corresponds to the maximum pore ratio in the middle and upper part of the laterite; Fe and Al are the most abundant elements on the surface of the phosphorus-contaminated laterite; the cement aggregate of the laterite is coated on the surface of the basic unit of the laterite; the area of phosphorus-contamin Macroscopic physical and mechanical properties of phosphorus-contaminated laterite under stress conditions: with the increase of phosphorus concentration, the relative quality of phosphorus-contaminated laterite, clay content increases, and silt content decreases; the limiting water content decreases; the maximum dry density increases, the optimal water content decreases, and exists. Microstructure characteristics of phosphorus-contaminated laterite: with the increase of phosphorus concentration, the cementation degree of microstructural units is higher, the bonding degree between units is lower, the porosity of phosphorus-contaminated laterite is lower, and the surface of flaky clay minerals is higher. Fine particle deposits are formed to form a new form of laterite structure. The cemented aggregates of phosphorus-contaminated laterite are still coated on the surface of the basic unit. The microstructure parameters of phosphorus-contaminated laterite are better than those before the loading. The change of mechanical properties of phosphorus-contaminated laterite is due to the weakening of the microstructure of phosphorus-contaminated laterite. The mechanism of action between laterite and its influence on macro and micro characteristics are as follows: the mechanism of action of phosphorus pollution on laterite and its influence on macro and micro characteristics can be explained by five actions of hydrolysis, adsorption complexation, reduction oxidation, salt formation and dissolution between phosphorus and laterite.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X53;TU43

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