含水量和含盐量对原状黄土力学特性的影响

发布时间：2018-04-25 04:00

本文选题：黄土 + 含水量　；参考：《华北水利水电大学》2017年硕士论文

【摘要】：近些年来,西部黄土地区(如甘肃、陕西等地)滑坡等地质灾害发生频繁,对当地人们的生命和财产安全带来了巨大的威胁,已成为制约当地经济发展的重要影响因素,因此分析滑坡的发生机理以及黄土力学特性的影响因素具有重要的理论与工程实际意义。本文以甘肃黑方台黄土为对象,通过现场调查、室内试验,研究了含水量及含盐量对黄土力学特性的影响规律。本文主要内容如下:(1)通过对不同含水量原状黄土的环剪试验,研究了黄土在不同含水量状态下的强度弱化规律,系统地分析了含水量对原状黄土力学特性的影响,分析发现:低含水量状态下的原状黄土呈应变软化特性,随着含水量的升高,其对应的应变软化特性逐渐减弱,剪应力-应变曲线逐渐向应变硬化型转变,在相同法向应力作用下,土样含水量越低,剪应力峰值越高,剪应力增长速度也越快,越快达到峰值;原状黄土的抗剪强度随着含水量的升高不断降低,但降低幅度逐渐减小,说明水对低含水量的黄土抗剪强度软化效应比高含水量黄土更加明显;随着含水量的升高,原状黄土的粘聚力逐渐下降,内摩擦角也逐渐降低,但降低幅度是不相同的,相对于粘聚力来说,内摩擦角随含水量增大而产生的降幅较小,这表明含水量对粘聚力具有较大的灵敏性。(2)通过对不同含盐量原状黄土的环剪试验,研究了黄土在不同含盐量下的强度变化规律,系统地分析了含盐量对原状黄土力学特性的影响,分析发现:在相同法向应力作用下,土样含盐量越高,剪应力峰值越高,剪应力增长速度也越快,同一含盐量状态下,法向应力越大,剪应力峰值越大,剪应力增大速度越快;随着含盐量的降低,原状黄土的抗剪强度不断降低,减小值随法向应力的增大而增大,此外盐分降低对高含盐量的黄土抗剪强度弱化作用比低含盐量黄土更明显;随着含盐量的降低,土体粘聚力和内摩擦角均逐渐降低,但内摩擦角降低幅度很小,这表明含盐量对粘聚力具有较大的灵敏性。
[Abstract]:In recent years, geological disasters such as landslides in the loess region of western China (such as Gansu, Shaanxi and other places) have occurred frequently, which have brought a great threat to the safety of local people's lives and property, and have become an important influencing factor restricting the development of local economy. Therefore, it is of great theoretical and practical significance to analyze the occurrence mechanism of landslide and the influencing factors of loess mechanical properties. Taking Heifangtai loess in Gansu province as an example, the influence of water content and salt content on the mechanical properties of loess was studied by field investigation and laboratory tests. The main contents of this paper are as follows: (1) through the annular shear test of loess with different moisture content, the strength weakening law of loess under different water content is studied, and the influence of water content on the mechanical properties of undisturbed loess is systematically analyzed. It is found that under the condition of low water content, the undisturbed loess shows strain-softening characteristics. With the increase of water content, the corresponding strain-softening characteristic decreases gradually, and the shear stress-strain curve gradually changes to the strain-hardening type. Under the same normal stress, the lower the water content of soil sample, the higher the peak value of shear stress, the faster the growth rate of shear stress and the faster the peak value of shear stress, the shear strength of undisturbed loess decreases with the increase of water content, but the decreasing range decreases gradually. The results show that the softening effect of water on the shear strength of loess with low water content is more obvious than that of loess with high water content, and with the increase of water content, the cohesion and internal friction angle of undisturbed loess decrease gradually, but the decrease range is different. Relative to cohesion, the decrease of internal friction angle is smaller with the increase of water content, which indicates that water content has greater sensitivity to cohesion. In this paper, the strength variation law of loess under different salt content is studied, and the influence of salt content on the mechanical properties of undisturbed loess is systematically analyzed. It is found that under the same normal stress, the higher the salt content of soil sample is, the higher the peak value of shear stress is. Under the same salt content, the greater the normal stress, the greater the peak value of shear stress and the faster the increase of shear stress, and with the decrease of salt content, the shear strength of undisturbed loess decreases continuously. The decreasing value increases with the increase of normal stress, in addition, the weakening effect of salinity on the shear strength of loess with high salt content is more obvious than that of loess with low salt content, and with the decrease of salt content, the cohesive force and internal friction angle of soil gradually decrease. However, the reduction of internal friction angle is very small, which indicates that salt content is sensitive to cohesion.
【学位授予单位】：华北水利水电大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S152

【参考文献】