饱和-非饱和重塑黄土变形强度特征

发布时间：2018-01-30 22:51

本文关键词： 重塑黄土含水量三轴试验强度特性应力-应变体应变　出处：《长安大学》2014年硕士论文　论文类型：学位论文

【摘要】：黄土是一种特殊性土，属于我国西北地区一种最常见的土工材料，既可以作为建筑材料使用，又是多种建筑依存的工程环境。诸多学者对黄土的分布、成因、行为特性和变形强度特性等方面的研究和实践均取得了显著成果，但是对于以初始含水量作为状态变量的饱和-非饱和黄土的应力-应变、体应变和强度特性的研究较少。本文在借鉴已有研究成果的基础上，以陕西省延安市Q2黄土为研究对象，应用改进后的非饱和土三轴试验仪，进行了控制含水量的饱和-非饱和重塑黄土（ρd=1.6g/cm3）常规三轴压缩应力路径（CTC）下的固结排水剪切试验。分别就不同初始含水量和围压状态下的应变结果定性进行了应力-应变特性和变形特性分析，就不同初始含水量条件下应力结果定量进行了强度特性分析。得出的结论如下：（1）重塑黄土的应力-应变曲线随初始含水量的增大逐渐由应变软化型向稳定型和应变硬化型转变，相应的直线、双曲函数和幂函数对其分别具有较好的拟合效果；围压对于重塑黄土的应力-应变形式不产生显著影响。（2）重塑黄土在受力时抵抗变形的能力随着含水量的增加而降低，产生的体积变化量也与含水量密切相关，低含水量的土体在剪切过程中发生“剪胀”现象，高含水量土体在剪切过程中产生“剪缩”现象；土体由膨胀到收缩的体积变化趋势还可以通过增加围压来实现。（3）重塑黄土粘聚力和内摩擦因数均随含水量的增加非线性降低，存在含水量特殊状态点控制着粘聚力与内摩擦角的转折和发展趋势，可利用特殊状态点将非线性关系表达为幂函数。本文采用含水量作为状态变量，对非饱和重塑黄土抗剪强度和极限荷载进行拟合，该拟合公式形式简单，参数少，，物理意义明确，拟合结果偏安全，因此，在工程实用中是一条计算任意含水量条件下土体强度的简便途径。
[Abstract]:Loess is a kind of special soil, which belongs to the most common geotechnical material in Northwest China. It can be used as building materials, and it is also a kind of engineering environment dependent on many kinds of buildings. Many scholars have studied the distribution and origin of loess. Remarkable achievements have been made in the research and practice of behavior characteristics and deformation strength characteristics, but the stress-strain of saturated-unsaturated loess with initial water content as the state variable has been obtained. There are few studies on bulk strain and strength characteristics. Based on the existing research results, this paper takes Q2 loess in Yanan City, Shaanxi Province as the research object, and applies the improved unsaturated soil triaxial test instrument. Saturated unsaturated remolded loess (蟻 _ d _ (1.6 g / cm ~ (3)) under normal triaxial compression stress path (CTC) was carried out to control water content. The stress-strain characteristics and deformation characteristics of strain results under different initial water content and confining pressure were qualitatively analyzed. The strength characteristics of the stress results under different initial water contents are analyzed quantitatively. The conclusions are as follows: 1) the stress-strain curve of remolded loess changes gradually from strain softening type to stable type and strain hardening type with the increase of initial water content. Hyperbolic function and power function have better fitting effect respectively. Confining pressure has no significant effect on the stress-strain form of remolded loess. (2) the ability to resist deformation of remolded loess decreases with the increase of water content, and the volume change is closely related to water content. The phenomenon of "shear expansion" occurs in the shear process of the soil with low water content, and the phenomenon of "shearing shrinkage" occurs in the shear process of the soil with high water content. The change of soil volume from expansion to contraction can also be achieved by increasing confining pressure. 3) the cohesive force and internal friction coefficient of remolded loess decrease nonlinear with the increase of water content, and there is a special point of water content controlling the turning point and developing trend of cohesion and internal friction angle. The nonlinear relation can be expressed as a power function by using special state points. In this paper, the water content is used as the state variable to fit the shear strength and ultimate load of unsaturated remolded loess. The fitting formula is simple in form, few in parameters, clear in physical meaning and safe in fitting results. It is a simple and convenient way to calculate the strength of soil under the condition of arbitrary water content in engineering practice.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU444;TU411

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