【作者】 王文军；

【导师】 朱向荣；

【作者基本信息】 浙江大学 ， 岩土工程， 2004， 博士

【摘要】 水泥土工程应用广泛，然而工程实践表明，水泥土强度不够高、形成的复合地基后期变形较大等问题制约了水泥土的进一步应用，选择适宜的外掺剂改善水泥土性能是解决这些问题的重要途径。随着纳米科技的发展以及纳米材料在混凝土等水泥基材料中的应用研究，在水泥土中掺加性能优异的纳米级材料将成为一种新的尝试。本文在纳米矿粉水泥土力学特性试验研究的基础上，探讨了纳米矿粉水泥土固化机理，为纳米材料进一步应用于水泥土提供微观层次上的依据。 在总结纳米材料在水泥基材料中的应用现状以及应用前景的基础上，本文首先分析了三种纳米矿粉的微结构特性及其与普通矿粉的微结构特性异同；通过水泥土室内无侧限抗压强度试验，探讨了纳米矿粉掺入比和龄期对水泥土强度的影响规律。试验结果表明，适宜的纳米硅粉掺入比下，各个龄期的水泥土强度显著提高；纳米铝粉对水泥土的增强效果不明显；直至90d时，纳米钛粉仍然降低水泥土强度。根据试验结果，分析了纳米硅粉水泥土的变形特性，并对其应力应变曲线进行了二次抛物线拟合分析，推导了曲线上升段的表达式。 结合水泥石强度试验和XRD试验，从火山灰效应、填充效应、水泥水化促进作用和微结构改善作用等方面探讨了三种纳米矿粉在水泥水化硬化过程中的作用机理；从这四个方面出发，对比分析了纳米硅粉和普通硅粉作用机理的异同点，分析表明，纳米硅粉的优异特性主要表现为颗粒细度、晶体结构、表面羟基等特性。 设计了三组室内试验，分别探讨了纳米硅粉对粘性土物理力学性能的影响；结合试验结果和土质学基本理论，提出从水分子吸附作用、胶结作用、填充作用三个方面探讨纳米硅粉与粘性土之间的作用机理。 结合SEM试验，探讨了纳米硅粉水泥土的微结构特点。在研究水泥浆—纳米硅粉、纳米硅粉—粘性土、水泥浆—粘性土相互作用的基础上，将纳米硅粉水泥土的固化机理总结为：水泥水化物的胶结作用、粘土颗粒中的离子交换效应和“二次反应”、纳米硅粉的火山灰效应、纳米硅粉的填充效应、纳米硅粉的胶结作用。根据固化机理，解释了水泥土和水泥石强度试验中的一些现象和规律，分析了纳米硅粉改性水泥土的适用性。 最后，通过室内试验分析了纳米硅粉水泥土的细观损伤机制及其损伤特性，建立了无侧限轴向压缩条件下的弹塑性损伤模型，分析了损伤演化规律。研究表明，纳米硅粉水泥土内部存在明显的损伤现象，掺加纳米硅粉，水泥土损伤特性发生改变：与试验曲线的对比结果表明，本文采用的损伤变量和损伤模型能够较真实地反映纳米硅粉水泥土的损伤特性。更多还原

【Abstract】 Cemented soil has been extensively used to ground treatment, however, engineering experiences suggest that low strength and large deformation has restricted its further application in the engineering. To improve engineering properties, many additives have been added to cemented soil. With the progress of nanometer technology, nanometer materials have been applied to modify cement-based materials, so it is a trail to introduce nanometer material with particular characteristics to cemented soil as a new kind of additive. In the paper, three kinds of nanometer materials are used for the cemented soil. Based on laboratory tests and theoretical analysis, the paper discussed reinforcement mechanism of the cemented soils stabilized the nanometer materials, which will provide research foundation for further application of the nanometer materials in cemented soil.Based on analysis on research existing status and application foreground of nanometer materials in cemented based material, the paper firstly discusses the microstructure properties of the three nanometer materials and compares them with the corresponding ordinary crystals. By unconfining compression strength tests of the cemented soil stabilized with the nanometer materials, influencing rules of nanometer material addition ratio and curing period on the strength are individually analyzed. The results suggest that nanometer silica fume (nanometer SiOx) can greatly improve the strength of cemented soil at various curing period, nanometer aluminium fume (nanometer AljOs) can not improve the strength, and nanometer titanium fume (nanometer TiO2) still reduce the strength until curing period of 90d. According to testing results, the stress-strain curve of the cemented soil stabilized the nanometer silica fume is fitted using a quadratic parabolic curve and expression equation for upward sector of the stress-strain curve is given.Through strength tests and XRD tests for cemented stone, the paper presents action mechanism of the nanometer materials in the cement hydration and hardening process: pozzolanic effect, filling effect, acceleration action for the cement hydration, and improving action for microstructure. From the four aspects, the modified mechanism of the nanometer silica fume and ordinary silica fume in cement paste are compared. The analysis results show that the particular properties of the nanometer silica fume include particle fineness, crystal structure and surface hydroxy, etc.A serial of laboratory tests are performed to study physical and mechanic properties of the clay with the addition of the nanometer silica fume. Based on testing results and soil theory, the modified mechanism of the nanometer silica fume in the clay is proposed: water molecule adsorption action, cementation action and filling action.Combining the SEM tests, the microstructure features of the cemented soil of nanometer silica fume are concluded. On the basis of analysis on the pairwise action of cement paste, nanometer silica fume and clay, the paper proposes the reinforcement mechanism of the cemented soil stabilized with nanometer silica fume. The reinforcement mechanism includes cementation action of cement hydrate, ionic exchange and quadrate reaction of clay particle, pozzolanic effect, filling effect and cementation action of nanometer silica fume. According to the reinforcement mechanism, some experimental phenomena and rules in the strength tests of cemented soil and cemented stone are explained. The paper also discusses the applicability of the nanometer silica fume in the cemented soil as an additive.Based on the analysis of micro-damage mechanism and damage performance of the cemented soil stabilized with nanometer silica fume, an elasto-plasticity damage model under uniaxial compression condition is established. Damage evolution laws are analyzed by the load-unload tests. Analysis results show that obvious damage occurs in the inner of the cemented soil stabilized with nanometer silica fume and the added nanometer silica fume can improve the damage更多还原