全吸力范围内桂林红黏土的土-水特征曲线及微观结构演化规律研究

发布时间：2018-05-21 00:25

本文选题：非饱和土 + 桂林红黏土　；参考：《北京交通大学》2017年硕士论文

【摘要】：土-水特征曲线(Soil Water Retention Curve)是描述非饱和土水力特性的重要关系曲线,它对非饱和土的诸多特性有影响,如渗透性、体变以及强度等。同时,作为解释非饱和土行为的一项基本本构关系,土-水特征曲线是将理论、试验及预测方法有机结合的重要关系之一,也是构筑非饱和土各种重要关系的基础。因此,通过土-水特征曲线研究非饱和土的相关性质具有重要的意义。影响土-水特征曲线的影响因素众多,包括土的类型、应力状态、孔隙比、孔隙分布、初始含水量、吸力范围、温度以及化学成分等等。现有研究表明,对于某一特定土样,孔隙比是影响土-水特征曲线最为直接和重要的因素。然而,当孔隙比相同时,不同微观孔隙结构的土样却表现出不同的土-水特征曲线性状。地基、路基以及边坡等实际工程中的土体,一方面由于受荷载作用而引起孔隙体积的减小;另一方面由于降雨、蒸发等气候因素影响,天然土体处于干湿循环过程之中,其孔隙比和微观孔隙结构也将发生改变,从而导致其工程响应的差异。为了研究不同孔隙结构对非饱和土土-水特征曲线的影响,以桂林红黏土为研究对象,首先自主研制单孔结构泥浆土制样装置,利用固结法和压实法分别制备单孔和双孔结构的土样。随后,基于轴平移法、滤纸法和饱和盐溶液蒸汽平衡法3种不同控制吸力的方法,对上述两种不同孔隙结构以及不同初始孔隙比的共计129个桂林红黏土土样的土-水特征曲线开展了试验研究。最后,利用压汞法与扫描电镜法,对泥浆土与压实土样在干化、湿化和干湿循环过程中不同吸力阶段的微观孔隙结构进行了试验研究,揭示了单、双孔结构土样在水力作用过程中微观孔隙结构的演化规律。取得的主要研究成果如下:(1)自主研制了单孔结构泥浆土制样装置,对不同孔隙结构土样制备方法进行了优化。自主开发研制了一种单孔结构泥浆土制样装置,其原理简单、使用方便,能够灵活地通过砝码或千斤顶控制固结压力,并可通过制样桶的刻度以及量筒所测排水量,对所制备土样的密度进行有效控制;同时,基于所研制的泥浆土制样装置和传统的压实样制样器,对单孔结构泥浆土和双孔结构压实土试样的制备方法进行了优化。(2)利用不同的吸力控制技术,开展了全吸力范围内不同孔隙结构桂林红黏土的土-水特征曲线试验研究,揭示了初始孔隙比和微观孔隙结构对土-水特征曲线的影响规律。针对桂林红黏土,通过单孔结构泥浆土制样装置制备3种初始孔隙比的单孔结构重塑土,通过击实法制备3种初始孔隙比的双孔结构重塑土。分别利用轴平移技术、滤纸法和饱和盐溶液蒸汽平衡法,对不同吸力水平的吸力进行控制,获取了不同孔隙结构和不同初始孔隙比条件下桂林红黏土的土-水特征曲线,揭示了微观孔隙结构和初始孔隙比对土-水特征曲线的影响规律,包括对干化曲线、湿化曲线以及滞回特性的影响。(3)通过对土样在干湿循环过程中的不同阶段开展压汞实验和电镜扫描实验,揭示了单、双孔结构的桂林红黏土在干湿循环过程中微观结构演化规律。利用压汞实验和扫描电镜实验,分别测试了 3种初始孔隙比的泥浆土样与压实土样在干湿循环过程中不同吸力阶段的微观孔隙结构,包括干化过程和湿化过程,从而揭示了两种不同孔隙结构桂林红黏土微观孔隙结构的演化规律,并重点分析了孔隙结构类型对土-水特征曲线滞回特性的影响。
[Abstract]:The soil water characteristic curve (Soil Water Retention Curve) is an important relation curve to describe the hydraulic characteristics of unsaturated soils. It affects many properties of unsaturated soils, such as permeability, volume change and strength. At the same time, as a basic constitutive relation of unsaturated soil behavior, the soil water characteristic curve is the theory, test and prediction method. One of the important relationships of organic combination is also the basis for the construction of various important relationships of unsaturated soils. Therefore, it is of great significance to study the related properties of unsaturated soils by the soil water characteristic curve. There are many factors affecting the soil water characteristic curve, including soil type, stress state, pore ratio, pore distribution, initial water content and suction. Scope, temperature and chemical composition and so on. Existing studies have shown that the ratio of pores is the most direct and important factor affecting the soil water characteristic curve for a specific soil sample. However, the soil samples with different micro pore structures show different characteristics of soil water characteristic curve when the pores are compared with phase. On the one hand, the volume of the soil is reduced by the load action. On the other hand, due to the influence of rainfall and evaporation, the natural soil is in the dry and wet cycle, and the pore ratio and micropore structure will also change, which leads to the difference in the response of the soil. With the soil water characteristic curve and the soil water characteristic curve, Guilin red clay is the research object. First, single hole structure mud and soil sample preparation device is independently developed. The single hole and double hole structure are prepared by consolidation method and compaction method respectively. Then, 3 different methods of controlling suction based on axial translation method, filter paper method and saturated salt solution steam balance method are used. The soil water characteristic curves of 129 Guilin red clay samples with different pore structures and different initial pore ratios were studied. Finally, the micro pore structure of the mud soil and the compacted soil samples at different suction stages during dry, wet and dry wet cycles were studied by using the method of mercury injection and scanning electron microscopy. The evolution law of micro pore structure of single and double pore structure soil samples during hydraulic action is revealed. The main achievements are as follows: (1) the single hole structure mud and soil sample preparation device has been independently developed, and the preparation methods of soil samples with different pore structures have been optimized. It is simple in principle and convenient to use. It can control consolidation pressure by weight or Jack flexibly, and can control the density of the prepared soil by making the scale of the sample barrel and measuring the amount of water in the cylinder. At the same time, the mud soil and the traditional compacted sample are developed for the single hole structure mud soil and the double hole. The preparation method of the compacted soil sample was optimized. (2) the soil water characteristic curve of the Guilin red clay with different pore structure in the full suction range was carried out by using different suction control techniques, and the influence of the initial pore ratio and the micro pore structure on the soil water characteristic curve was revealed. In view of the Guilin red clay, the single soil water characteristic curve was revealed. A single pore structure remolded soil with 3 initial pore ratios is prepared by a hole structure mud soil sample preparation device. A double pore structure remolding soil with 3 initial pore ratios is prepared by compaction method. The suction forces of different suction levels are controlled by axial translation technique, filter paper method and saturated salt solution vapor equilibrium method, and different pore structures and different initial stages are obtained. The soil water characteristic curve of Guilin red clay under the initial pore ratio revealed the influence of the micro pore structure and initial pore ratio on the soil water characteristic curve, including the influence on the drying curve, the wetting curve and the hysteresis characteristics. (3) the pressure mercury experiment and the SEM scanning were carried out at different stages during the dry and wet cycle of the soil sample. The microscopic structure evolution of the single, double pore structure of Guilin red clay in the dry and wet cycle was revealed. The micro pore structure of the mud soil samples and compacted soil samples at different suction stages during the dry and wet cycle were measured by the mercury pressure test and the scanning electron microscope. The drying process and the wetting process were also tested, respectively. The evolution of micro pore structure of two different pore structures of Guilin red clay is revealed, and the effect of pore structure type on the hysteresis characteristics of soil water characteristic curve is analyzed.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU446

【参考文献】