不同pH值下红土的宏微观特性研究

发布时间：2018-09-19 10:57

【摘要】：本文在综合分析污染土的危害、污染土的宏观特性研究、土体的微结构特性研究以及污染土腐蚀机理研究的基础上,明确了目前污染土研究中存在的问题,针对云南红土,选取盐酸和氢氧化钠调节溶液的pH值,开展了pH值变化对云南红土性质影响的研究,主要包括红土的击实特性、直剪特性、压缩特性、微结构特性、影响机理,为有效防治水环境的安全以及基础设施工程的安全提供理论依据。击实红土的宏微观特性表明：浸润时间一定,随pH值升高,红土的最大干密度存在一个极大值和一个极小值,最优含水率逐渐减小。pH值一定,随养护时间延长,红土的最大干密度存在两个极大值和一个极小值,最优含水率存在一个极大值和两个极小值。随pH值增大,从酸性到碱性的过程,击实红土的微结构图像呈现出密实性变差的特征,对应的微结构参数呈现出孔隙率增大、颗粒数减小、颗粒分布分维存在极大值、颗粒定向度减小的特征。剪切红土的宏微观特性表明：养护时间一定,随pH值的升高,红土的抗剪强度、黏聚力、内摩擦角存在极大值。pH值一定,随养护时间延长,红土的抗剪强度、黏聚力、内摩擦角逐渐减小。偏酸性或偏碱性条件下,剪前和剪后红土微结构图像呈现出抗剪性变差特征,对应微结构参数孔隙率增大、颗粒数减小、颗粒分布分维和颗粒定向度减小。随着养护时间的延长,红土微结构图的孔隙增大、颗粒数减少、颗粒分布分维和颗粒定向度减小。压缩红土的宏微观特性表明：养护时间一定,pH值较低的酸性条件,红土不易被压缩；pH值较高,碱性浓度较低时,红土不易压缩,碱性浓度高时,红土易压缩。pH值一定,随养护时间延长,红土逐渐变得易压缩。随pH值增大,从酸性到碱性的过程,压缩前红土的微结构图像呈现出微结构参数孔隙率增大、颗粒数减小、颗粒分布分维和颗粒定向度减小,压缩后红土的微结构图像呈现出压缩性增强特征,对应的微结构参数孔隙率增大、颗粒数减小、颗粒分布分维减小、颗粒定向度减小。随养护时间延长,红土微结构图的孔隙增大、颗粒数减少、颗粒分布分维和定向度减小。pH值变化对红土的击实特性、抗剪特性、压缩特性的影响,可以从不同的pH值溶液与红土之间的浸润作用、侵蚀作用、水解胶结作用、溶解作用来说明,对应的微结构特性和化学组成成分也随之发生改变。
[Abstract]:On the basis of synthetically analyzing the harm of contaminated soil, the macroscopic characteristic of polluted soil, the microstructure of soil and the corrosion mechanism of contaminated soil, the problems existing in the study of contaminated soil are clarified in this paper, aiming at the red soil in Yunnan. The influence of the change of pH value on the properties of Yunnan laterite was studied by selecting the pH value of hydrochloric acid and sodium hydroxide adjusting solution, including compaction, direct shear, compression, microstructure and influence mechanism of laterite. It provides a theoretical basis for effectively preventing and controlling the safety of water environment and the safety of infrastructure engineering. The macroscopical and microscopic properties of compacted red soil indicate that the maximum dry density of red soil has a maximum value and a minimum value with the increase of pH value, and the optimum moisture content decreases gradually with the increase of curing time. There are two maximum values and one minimum value for the maximum dry density of the red soil and one maximum and two minimum values for the optimal moisture content. With the increase of pH value, the microstructural images of compacted laterite show the characteristics of poor compactness, the porosity increases, the number of particles decreases, and the fractal dimension of particle distribution is maximized. The characteristic of decreasing particle orientation. The macroscopical and microscopic properties of the shear laterite show that the shear strength, cohesion and internal friction angle of the red soil have a maximum value of pH value with the increase of pH value, and the shear strength and cohesion force of the red soil increase with the curing time. The angle of internal friction decreases gradually. Under the condition of partial acidity or alkalinity, the microstructural images of laterite before and after shearing showed a variation of shear resistance, the porosity of the corresponding microstructural parameters increased, the number of particles decreased, the distribution of particles and the orientation of particles decreased. With the prolongation of curing time, the pore size increases, the number of particles decreases, and the particle distribution and particle orientation decrease. The macroscopical and microscopic properties of compressed laterite show that the curing time is constant and the pH value is low, the pH value of red soil is not easy to be compressed, the red soil is not easy to compress when the alkaline concentration is low, and when the alkaline concentration is high, the red soil is easy to compress. With the increase of curing time, the red soil becomes more and more compressible. With the increase of pH value, the microstructural images of laterite before compression showed that the porosity of microstructural parameters increased, the number of particles decreased, the distribution of particles and the orientation of particles decreased during the process from acidity to alkalinity. The microstructural images of red soil show the characteristics of compressibility enhancement, the porosity of the corresponding microstructural parameters increases, the number of particles decreases, the fractal dimension of particle distribution decreases, and the orientation of particles decreases. With the increase of curing time, the pore size of red soil microstructural map increases, the number of particles decreases, and the particle distribution and orientation decrease. The effects of the change of particle distribution and orientation on the compaction, shear and compression properties of laterite are discussed. It can be explained from the infiltration, erosion, hydrolytic cementation and dissolution between different pH value solutions and laterite. The corresponding microstructure and chemical composition also change.
【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】：TU43;X53

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