不同初始干密度非饱和黏性土强度特性研究

发布时间：2018-03-20 22:53

本文选题：干密度　切入点：土-水特征曲线　出处：《湖北工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：地球地表环境(除海域面积外)大部分区域都是干旱或者半干旱地区,在这些地区中广泛存在的土体多处于非饱和状态。随着岩土力学理论研究的进步、科学技术的发展以及实际工程对非饱和土理论的需求,非饱和土的研究已经成为了国内外岩土界学者们关注的热点问题。目前非饱和土的强度理论众多,强度理论的特征参数的定义也各有不同,在选用强度公式和参数时也没有像饱和土有着统一广泛的标准。因此,针对非饱和土的强度特性展开定性的研究有着重要的意义。本文以非饱和土的经典强度理论为前提,历时一年半时间针对非饱和武汉黏性土展开了不同初始干密度下的土-水特征曲线试验、饱和土三轴试验以及非饱和土三轴试验。在试验数据处理的基础上,结合理论分析,对非饱和武汉黏性土强度参数的变化规律和经典非饱和土强度公式的适用性进行了探索研究,具体研究和结论如下:(1)通过压力板仪试验,对试验用土的土-水特征曲线特性展开了研究。试验表明,不同的初始干密度主要影响了试样的初始含水率和大孔径孔隙的数量,对小孔经孔隙的影响不明显;在低吸力区间的脱湿过程中,干密度较大的试样含水率以及脱湿速率都明显小于干密度小的试样;当吸力值逐渐增大,不同初始干密度试样的脱湿速率趋于一致且含水量差异减小。(2)对土-水特征曲线试验数据,利用模型拟合分析,发现试样的进气值与干密度呈现正相关,而残余含水率与干密度无明显相关性。(3)对试验用非饱和土展开不同试验环境下的三轴试验,试验结果表明黏性土的破坏为剪胀破坏,变形呈现明显的“鼓”形,变形受到干密度和基质吸力的抑制较为明显;应力应变曲线为应变硬化型,无明显峰值,15%的应力峰值与干密度、净围压以及基质吸力均表现出正相关。(4)通过处理和分析试验中的数据,发现土体强度参数b?与基质吸力和净围压均表现出负相关;其值受到干密度的影响,但无明显相关性。(5)通过对有效应力参数?的研究,发现其可以用来评价净法向力和基质吸力对强度贡献的相对程度;其预测值与干密度强度呈现正相关,实测值与净围压表现出负相关,受到干密度和基质吸力的影响却无明显相关性。(6)对于两种不同的预测方法和预测公式,结合试验数据,通过不同条件下的预测值和实测值的对比,针对非饱和武汉黏性土的强度预测研究给出定性的分析,并给出相应的方法和公式建议。
[Abstract]:Most of the earth's surface environment (except the sea area) is arid or semi-arid, in which the soil mass is mostly unsaturated. With the development of science and technology and the demand of unsaturated soil theory in practical engineering, the research of unsaturated soil has become a hot issue of geotechnical scholars at home and abroad. At present, there are many strength theories of unsaturated soil. The definition of characteristic parameters in strength theory is different, and there is no uniform and extensive standard in choosing strength formula and parameter as in saturated soil. The qualitative study on the strength characteristics of unsaturated soils is of great significance. In this paper, the classical strength theory of unsaturated soils is the premise. The soil-water characteristic curve test, saturated soil triaxial test and unsaturated soil triaxial test under different initial dry densities were carried out in a period of one and a half years for unsaturated Wuhan clay. The variation law of strength parameters of unsaturated clay in Wuhan and the applicability of classical unsaturated soil strength formula are studied. The concrete research and conclusion are as follows: 1) through the pressure plate test, The characteristics of soil-water characteristic curve of soil for test are studied. The results show that different initial dry density mainly affects the initial moisture content and the number of pore size of the sample, but has no obvious effect on the pore size. In the process of dehumidification in the low suction region, the moisture content and the dehumidification rate of the sample with higher dry density are obviously smaller than those of the sample with low dry density, and when the suction value increases gradually, The experimental data of soil-water characteristic curve of different initial dry density samples tend to be consistent and the difference of water content decreases. The model fitting analysis shows that the inlet air value of the sample has a positive correlation with the dry density. However, there is no obvious correlation between residual moisture content and dry density. The deformation was inhibited by dry density and matrix suction, the stress-strain curve was strain-hardening type, and there was no obvious peak value of 15% of stress peak and dry density. Net confining pressure and matrix suction showed positive correlation. There was a negative correlation with the matrix suction and net confining pressure, and its value was affected by the dry density, but not by the effective stress parameter. It is found that it can be used to evaluate the relative degree of net normal force and matrix suction contribution to strength, the predicted value is positively correlated with dry density strength, and the measured value is negatively correlated with net confining pressure. Affected by dry density and matrix suction, however, there is no obvious correlation.) for two different prediction methods and formulas, combined with experimental data, the predicted and measured values under different conditions are compared. Based on the strength prediction of unsaturated Wuhan clay soil, the qualitative analysis is given, and the corresponding methods and formula suggestions are given.
【学位授予单位】：湖北工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU43

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