水泥土无侧限抗压强度影响因素研究

发布时间：2018-02-23 21:31

本文关键词： 水泥土无侧限抗压强度应力-应变关系影响因素　出处：《西北农林科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着西北大开发的深入,在我国西北地区修建了大量的道路工程和水利工程。黄土是西北地区主要的建筑材料之一,然而由于黄土具有湿陷性、非饱和性、震陷性等特性,黄土的强度往往不能满足实际建筑工程的需要,例如地基沉降和路基承载力问题。为了满足工程要求,实际工程中一般掺入水泥、石灰等,对黄土进行改良。水泥土是以土为主要骨料,以硅酸盐水泥为胶凝材料,以外加剂为改善其工程性能的补充添加物,以水为反应媒介所组成的混合物,经过拌和、振捣和养护而形成的具有特殊工程特性的坚硬材料。它具有抗压强度高,抗冻、抗渗、抗蚀和抗冲刷、耐久性能好等优点,被广泛用于路面基层、边坡加固、防渗里衬、地基稳定和夯土建筑的墙体材料中。本文依据前人的成果,以陕西延安安塞玉泉寺水库筑坝土料为加固对象,以无侧限抗压强度试验为试验方法,研究了水泥掺量、干密度、含水率、养护龄期和养护方式对水泥土无侧限抗压强度和应力-应变关系的影响,得出了以下结论。(1)随着水泥掺量的增加,水泥土的最大干密度和最优含水率都有很小幅度增加,而且水泥土的无侧限抗压强度呈线性增长。在同样水泥掺量的条件下,随着干密度的增加,水泥土无侧限抗压强度呈线性增长;随着含水率的增加,水泥土无侧限抗压强度呈二次函数形式衰减;随着养护龄期的增长,水泥土无侧限抗压强度呈幂函数形式增长。(2)水泥土应力-应变关系曲线都可分为压密阶段、弹性阶段、塑性强化阶段和应力衰减阶段4个阶段;水泥掺量和养护龄期的增加能够减小水泥土的弹塑性变形;干密度和含水率的增加能够增加水泥土的弹塑性变形。(3)采用不同组合盐溶液(Na2SiO3、NaOH和Na2SO4)浸泡养护水泥土,通过改变3种溶质的组合方式,研究出对水泥土无侧限抗压强度增强最显著的溶液组合。通过对正交试验结果的极差分析和方差分析,确定了盐溶液最优组合为(Na2SiO3)3(NaOH)1(Na2SO4)2,也可称为312溶液。(4)无论龄期如何变化,无侧限抗压强度由高到低的排序均为:312溶液浸泡养护→饱和石灰水浸泡养护→标准养护。312溶液浸泡养护和饱和石灰水浸泡养护水泥土试样的强度随着龄期的增加会趋于平缓。(5)标准养护下随着养护龄期的增加水泥土弹塑性变形减小,脆性越来越明显;312溶液浸泡养护可以增加水泥土弹塑性变形并提高其塑性,但会随着龄期的增加其提高幅度会趋于平缓;饱和石灰水浸泡养护不能增加水泥土的弹塑性变形,但能维持水泥土的塑性保持不变。
[Abstract]:With the development of Northwest China, a large number of road projects and water conservancy projects have been built in Northwest China. Loess is one of the main building materials in Northwest China. However, loess has the characteristics of collapsibility, unsaturated property, earthquake subsidence and so on. The strength of loess often can not meet the needs of actual construction projects, such as foundation settlement and subgrade bearing capacity. The cement soil is a mixture composed of soil as main aggregate, Portland cement as cementitious material, admixture as supplementary additive to improve its engineering performance, and water as reaction medium. A hard material with special engineering characteristics formed by vibration and maintenance. It has the advantages of high compressive strength, anti-freezing, impermeability, corrosion and erosion resistance, good durability, etc., and is widely used in pavement base, slope reinforcement, impermeable lining, etc. In the wall material of foundation stabilization and rammed earth building, based on the achievements of predecessors, this paper takes the earth material of Ansai Yuquan Reservoir in Yan'an, Shaanxi Province as the reinforcement object, takes the unconfined compressive strength test as the test method, studies the content of cement and the dry density. The influence of moisture content, curing age and curing mode on the unconfined compressive strength and stress-strain relationship of cement-soil is obtained. The following conclusion is drawn: (1) with the increase of cement content, The maximum dry density and optimum moisture content of cement-soil increased slightly, and the unconfined compressive strength of cement-soil increased linearly. The unconfined compressive strength of cement-soil increases linearly; with the increase of moisture content, the compressive strength of cement-soil decreases in the form of quadratic function; with the increase of curing age, the unconfined compressive strength of cement-soil decreases in the form of quadratic function. The stress-strain relationship curves of cement-soil can be divided into four stages: compaction stage, elastic stage, plastic strengthening stage and stress attenuation stage. The increase of cement content and curing age can reduce the elastoplastic deformation of cement-soil, and the increase of dry density and moisture content can increase the elastic-plastic deformation of cement-soil. By changing the combination of three solutes, the solution combination, which can enhance the compressive strength of cement-soil without lateral limit, is studied, and the results of orthogonal test are analyzed by means of range analysis and variance analysis. The optimum combination of salt solution was determined as Na2SiO3O3NNaOHN1Na2SO4Ni2, also called 312 solution. 4) No matter how the age changed, the order of unconfined compressive strength from high to low was that of soaking and curing in solution of: 312. 鈫扴aturated Limestone soaking maintenance. 鈫扵he strength of the cement soil sample treated with standard curing. 312 solution immersion and saturated lime water immersion curing will tend to be gentle with the increase of age.) under standard curing condition, the elastoplastic deformation of cement soil will decrease with the increase of curing age. Embrittlement is becoming more and more obvious. Soaking and curing in solution can increase the elastoplastic deformation and plasticity of cement-soil, but with the increase of age, the increase will tend to be gentle, and saturated lime water soaking and curing can not increase the elastic-plastic deformation of cement-soil. But it can keep the plasticity of cement soil unchanged.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU43

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