重塑非饱和坡积黏土土水特征曲线及强度特性的试验研究

发布时间：2018-08-26 19:14

【摘要】：非饱和坡积土的力学性能和强度特性是目前岩土工程界研究的热点和难点,由于非饱和土的工程性质复杂,以及对非饱和土的研究理论还不够完善,由非饱和土引起的边坡塌陷和泥石流等灾害问题不断频发,这给人民的生命财产安全带来了严重的威胁。针对这一问题,本文以湘潭北站附近某边坡的坡积土为研究对象,开展了多组基质吸力、饱和度和干密度的抗剪强度试验及重塑非饱和坡积黏土的土水特征曲线试验,对其力学性能和强度特性进行了系统而深入的研究,并建立了各自的强度理论公式,可为工程实践提供参考,本文研究成果如下:(1)对所取的坡积土进行了基本的物理特性试验,确定该土样的比重、液限、塑限、最大干密度、最佳含水率、不均匀系数、曲率系数等基本物理指标,最终判定该坡积土为级配不良的含砂高液限黏土,代号为CHS。(2)建立了土水特征曲线数学模型,运用该模型预测出土水特征曲线的残余段,并与具有代表性的Gardner模型、Van Genucheten模型、Mckee和Bumb模型拟合的土水特征曲线进行了比较分析,论证了本文所建数学模型的可靠性和合理性。(3)通过非饱和应变控制式直剪仪试验,发现重塑非饱和坡积黏土的固结量随着荷载的施加而急剧增大,最终趋于稳定。剪应力应变曲线在较低应力下呈剪切软化,在较高应力下,先表现为剪切硬化,后表现为剪切塑性。抗剪强度随着基质吸力的增大呈分段特性,在各阶段呈线性增长。(4)在上述试验基础上,建立了重塑非饱和坡积黏土分段的抗剪强度破坏包络面和分段的重塑非饱和坡积黏土抗剪强度公式。其中,干密度越大,重塑非饱和坡积黏土的总应力抗剪强度越高。当饱和度从饱和状态到残余状态时,重塑非饱和坡积黏土的抗剪强度表现为先增加,后减小,最终趋于稳定。(5)重塑的坡积黏土的黏聚力从饱和状态到残余状态,也呈现增、减和稳定三个阶段,变化规律近似呈正态分布,内摩擦角随着饱和度的增大,呈现非线性减小。同时发现,黏聚力随着干密度的增大而增大,但是内摩擦角随干密度的增加,变化不大。
[Abstract]:The mechanical properties and strength characteristics of unsaturated slope soil are hot and difficult in geotechnical engineering field at present. Because of the complexity of engineering properties of unsaturated soil, and the research theory of unsaturated soil is not perfect enough, Slope collapse and debris flow caused by unsaturated soil are constantly occurring, which brings serious threat to the safety of people's life and property. In order to solve this problem, this paper takes the slope soil of a slope near Xiangtan North Station as the research object, and carries out the shear strength test of multiple groups of matrix suction, saturation and dry density, and the soil-water characteristic curve test of remolding unsaturated slope clay. The mechanical properties and strength properties of the soils are studied systematically and deeply, and their strength theoretical formulas are established, which can be used as reference for engineering practice. The research results are as follows: (1) the basic physical properties of the slope soil are tested. The specific gravity, liquid limit, plastic limit, maximum dry density, optimum moisture content, uneven coefficient, curvature coefficient and other basic physical indexes of the soil sample are determined. The mathematical model of soil-water characteristic curve was established by code name CHS. (2), and the residual section of soil-water characteristic curve was predicted by using this model. It was compared with the soil-water characteristic curve fitted by Gardner model Van Genucheten model and Bumb model. The reliability and reasonableness of the mathematical model established in this paper are demonstrated. (3) through the experiment of the unsaturated strain controlled direct shear instrument, it is found that the consolidation of the remolded unsaturated slope clay increases sharply with the application of the load, and finally tends to be stable. The shear stress-strain curve shows shear softening at lower stress and shear hardening at higher stress, then shear plasticity. The shear strength increases linearly with the increase of the matrix suction. (4) based on the above experiments, the shear strength increases linearly. The shear failure envelope surface of remolded unsaturated slope clay and the formula of shear strength of remolded unsaturated slope clay are established. The higher the dry density, the higher the total stress shear strength of remolded unsaturated slope clay. When saturation is from saturation state to residual state, the shear strength of remolded unsaturated slope clay increases first, then decreases, and finally tends to be stable. (5) the cohesive force of remolded slope clay increases from saturation state to residual state. In the three stages of subtraction and stabilization, the law of variation is approximately normal distribution, and the angle of internal friction decreases with the increase of saturation. It is also found that the cohesion increases with the increase of dry density, but the angle of internal friction does not change with the increase of dry density.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU43

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