粘性土渗透破坏及长期渗透劣化试验研究
发布时间：2018-08-22 20:17
【摘要】：随着城市化进程的不断加快,全国各地高楼大厦相继拔地而起,城市轨道交通建设也迎来发展高峰,各地水利堤防工程也相继建设完善,这些工程大多都涉及到复杂多变的粘性土地层。由于粘性土地层长期经受地下水的渗透作用,粘性土的物理力学性能、结构等都会发生缓慢劣化,大量岩土工程事故也都证明了土体渗透破坏产生的危害巨大。因此探究粘性土渗透破坏和长期渗透条件下损伤劣化实质具有重要意义。本文主要开展了以下几个方面研究:(1)针对粘性土进行了界限含水率、比重、颗粒分析、击实、固结、直剪等一系列基本物理力学性质试验,重点阐述了粘性土的压缩性能和抗剪强度。试验得出粘性土变形量随着含水率和竖向荷载的增大而增大;土样粘聚力随着干密度的增大而增大,随着均值粒径的增大而减小;内摩擦角随着干密度的增大而减小,随着均值粒径的增大而增大,但相关性和幅度均较小;粘聚力随不均匀系数的增大而较小,内摩擦角随不均匀系数的增大而增大;粘聚力随曲率系数的增大而减小,内摩擦角随曲率系数的增大基本不变;(2)利用自制的渗透破坏仪研究了各单一粒径和混合粒径土样在各干密度下的渗透破坏临界坡降大小。对于单一粒径级土样,干密度对土体渗透破坏临界坡降影响最为显著,均值粒径次之,临界坡降随干密度三次方的增加而线性增加,随均值粒径的增加而线性减小;对于混合粒径的粘性土,不均匀系数对土体渗透破坏临界坡降影响较为显著,曲率系数次之,临界坡降随不均匀系数、曲率系数的增加而线性减小;(3)采用变水头渗透仪对不同干密度土样在不同PH值渗透液下进行长期渗透试验。试验得到各干密度土样在各PH值的渗透液长期渗透作用下,渗透系数均随着渗透时间得增大而减小;以PH=7的蒸馏水为液渗透的土样初始渗透系数总是大于以PH=3的盐酸为渗透液土样的初始渗透系数;经过长期渗透后,较小干密度土样在酸性渗透液渗透后其渗透系数大于以蒸馏水为渗透液渗透后的土样,较大干密度的土样则相反;高压实度土体在各PH值渗透液渗透后,其土体浸出液所含钠、钾、钙、镁离子浓度均小于低压实度土体;且土体浸出液中钙离子含量最高,钠、镁离子浓度次之,钾离子浓度最低。
[Abstract]:With the continuous acceleration of the urbanization process, the high-rise buildings in various parts of the country have emerged one after another, the construction of urban rail transit has also ushered in the peak of development, and the water conservancy and levee projects in various places have been built and perfected one after another. Most of these projects involve complex and changeable clay layers. Because the viscous soil layer is subjected to the infiltration of groundwater for a long time, the physical and mechanical properties, structure and so on of clay soil will slowly deteriorate. A large number of geotechnical engineering accidents have also proved that the damage caused by soil seepage failure is great. Therefore, it is of great significance to explore the essence of permeability failure and damage deterioration of cohesive soil under long-term permeation conditions. In this paper, the following aspects have been studied: (1) A series of basic physical and mechanical properties such as limit moisture content, specific gravity, particle analysis, compaction, consolidation, direct shear and so on have been carried out for cohesive soils. The compressive properties and shear strength of clay are described in detail. The results show that the deformation of cohesive soil increases with the increase of moisture content and vertical load, the cohesive force increases with the increase of dry density and decreases with the increase of mean particle size, and the angle of internal friction decreases with the increase of dry density. With the increase of the mean particle size, the correlation and amplitude are smaller, the cohesion force is smaller with the increase of the non-uniform coefficient, the internal friction angle increases with the increase of the non-uniform coefficient, and the cohesion force decreases with the increase of the curvature coefficient. The angle of internal friction is almost unchanged with the increase of curvature coefficient. (2) the critical slope of permeation failure of soil samples with single particle size and mixed particle size at various dry densities is studied by using a self-made permeation failure instrument. For soil samples with single particle size, dry density has the most significant effect on the critical slope of soil permeability failure, the mean particle size is the second, the critical gradient increases linearly with the increase of dry density to the third power, and decreases linearly with the increase of mean particle size. For clayey soil with mixed particle size, the influence of inhomogeneous coefficient on the critical slope of soil seepage failure is significant, the curvature coefficient is the second, and the critical slope gradient is with the non-uniform coefficient. (3) soil samples with different dry densities were subjected to long-term permeation experiments with different PH values. (3) soil samples with different dry densities were subjected to long-term permeation tests with varying water head osmometers. The results showed that the permeability coefficient of soil samples with different PH values decreased with the increase of permeation time. The initial permeability coefficient of soil sample with distilled water of PH=7 is always higher than that with hydrochloric acid of PH=3. The permeability coefficient of soil samples with small dry density is larger than that of soil samples with distilled water as osmotic solution, but the soil sample with higher dry density has the opposite effect after permeation of acid osmotic solution, the sodium content of soil leachate of high pressure solid soil is higher than that of soil sample with higher dry density. The concentration of potassium, calcium and magnesium is lower than that of low compaction soil, and the content of calcium is the highest in the leachate, followed by the concentration of sodium and magnesium, and the concentration of potassium is the lowest.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU442
本文编号：2198187
[Abstract]:With the continuous acceleration of the urbanization process, the high-rise buildings in various parts of the country have emerged one after another, the construction of urban rail transit has also ushered in the peak of development, and the water conservancy and levee projects in various places have been built and perfected one after another. Most of these projects involve complex and changeable clay layers. Because the viscous soil layer is subjected to the infiltration of groundwater for a long time, the physical and mechanical properties, structure and so on of clay soil will slowly deteriorate. A large number of geotechnical engineering accidents have also proved that the damage caused by soil seepage failure is great. Therefore, it is of great significance to explore the essence of permeability failure and damage deterioration of cohesive soil under long-term permeation conditions. In this paper, the following aspects have been studied: (1) A series of basic physical and mechanical properties such as limit moisture content, specific gravity, particle analysis, compaction, consolidation, direct shear and so on have been carried out for cohesive soils. The compressive properties and shear strength of clay are described in detail. The results show that the deformation of cohesive soil increases with the increase of moisture content and vertical load, the cohesive force increases with the increase of dry density and decreases with the increase of mean particle size, and the angle of internal friction decreases with the increase of dry density. With the increase of the mean particle size, the correlation and amplitude are smaller, the cohesion force is smaller with the increase of the non-uniform coefficient, the internal friction angle increases with the increase of the non-uniform coefficient, and the cohesion force decreases with the increase of the curvature coefficient. The angle of internal friction is almost unchanged with the increase of curvature coefficient. (2) the critical slope of permeation failure of soil samples with single particle size and mixed particle size at various dry densities is studied by using a self-made permeation failure instrument. For soil samples with single particle size, dry density has the most significant effect on the critical slope of soil permeability failure, the mean particle size is the second, the critical gradient increases linearly with the increase of dry density to the third power, and decreases linearly with the increase of mean particle size. For clayey soil with mixed particle size, the influence of inhomogeneous coefficient on the critical slope of soil seepage failure is significant, the curvature coefficient is the second, and the critical slope gradient is with the non-uniform coefficient. (3) soil samples with different dry densities were subjected to long-term permeation experiments with different PH values. (3) soil samples with different dry densities were subjected to long-term permeation tests with varying water head osmometers. The results showed that the permeability coefficient of soil samples with different PH values decreased with the increase of permeation time. The initial permeability coefficient of soil sample with distilled water of PH=7 is always higher than that with hydrochloric acid of PH=3. The permeability coefficient of soil samples with small dry density is larger than that of soil samples with distilled water as osmotic solution, but the soil sample with higher dry density has the opposite effect after permeation of acid osmotic solution, the sodium content of soil leachate of high pressure solid soil is higher than that of soil sample with higher dry density. The concentration of potassium, calcium and magnesium is lower than that of low compaction soil, and the content of calcium is the highest in the leachate, followed by the concentration of sodium and magnesium, and the concentration of potassium is the lowest.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU442
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