低有效应力状态下饱和砂土渗透与变形特性研究

发布时间：2018-03-21 10:32

本文选题：砂土液化　切入点：低有效应力　出处：《中国矿业大学》2014年硕士论文　论文类型：学位论文

【摘要】：我国是一个地震多发国家，震后引起的饱和砂土液化问题是岩土工程界研究的热点与难点之一。目前针对砂土液化的影响因素、液化产生机理、液化势的判别等方面已有很多研究成果，并得到广泛认可。而对于饱和砂土液化后在低有效应力状态下土体的应力应变行为认识尚不充分，而且现有的研究中很少或没有考虑伴有超孔隙水压力的消散过程中，孔隙水渗流对液化后砂土受力变形特性的关联影响。基于此，本文采用了室内实验及数值模拟的技术深入研究了饱和砂土在低有效应力状态下渗透和变形特性。（1）以土体重固结理论为基础，结合砂沸机理，对常规常水头渗透试验装置做了改进，获得了一套可测定饱和砂土处于低有效应力状态下的渗透系数的渗透试验装置，并对该装置的使用方法及试验步骤做了详细介绍。（2）利用新的渗透试验装置进行渗透试验研究，对颗粒级配不同的三种砂土在低有效应力状态下的渗透特性做了研究。试验发现，在有效应力为零时，他们的渗透系数都有不同程度的增大。其中XZ砂变化最大，其渗透系数为液化前的4倍左右；1#砂增幅次之，为液化前的2.5倍左右；2#砂增幅最小，为液化前1.5倍左右。随着有效应力的增大，砂土的渗透系数也在慢慢减小，其中1#砂和2#砂最终都恢复到初始值左右，而XZ砂最终保持在初始渗透系数的2.2倍左右。（3）利用全自动三轴仪模拟饱和砂土在低有效应力状态下的静力加载过程。试验结果表明，在本试验条件下的饱和砂土在不同有效应力状态下的静力再加载应力应变曲线可分为三个阶段：低强度阶段、强度恢复阶段和应变软化阶段。文章中还从砂土的初始相对密实度、砂土液化程度的不同、土层的埋置深度等三个方面研究了它们对应力~应变曲线发展趋势的影响。（4）结合三轴试验结果以及渗透试验结果，，本文将有效应力与初始有效应力之比'0'50%的饱和砂土所处的应力状态定义为低有效应力状态。（5）将低有效应力状态下土体的渗透和变形特性研究成果整合到数值模拟分析中，研究了砂性土边坡在孔隙水压力作用下伴随着孔隙水自下而上的渗流的边坡安全稳定性。
[Abstract]:China is an earthquake-prone country. The problem of saturated sand liquefaction caused by earthquake is one of the hot and difficult problems in geotechnical engineering. Many research achievements have been made on the determination of liquefaction potential, which has been widely accepted. However, there is still insufficient understanding of the stress-strain behavior of saturated sandy soil under low effective stress state after liquefaction. Moreover, in the present research, the influence of pore water seepage on the deformation characteristics of sand soil after liquefaction is seldom or not taken into account in the process of dissipation with excess pore water pressure. In this paper, the permeability and deformation characteristics of saturated sand under low effective stress are studied by laboratory experiments and numerical simulation. 1) based on the consolidation theory of soil weight and combined with the mechanism of sand boiling, a set of permeation test equipment for measuring the permeability coefficient of saturated sand under low effective stress is obtained by improving the conventional constant head permeation test device. The application method and test procedure of the device are introduced in detail. 2) the permeability characteristics of three kinds of sand with different particle gradation under low effective stress state are studied by using a new permeation test device. The experimental results show that the effective stress is 00:00, Among them, XZ sand has the biggest change, and its permeability coefficient is about 4 times of that before liquefaction, followed by the increase of sand about 2.5 times before liquefaction and the smallest increase of sand before liquefaction. With the increase of effective stress, the permeability coefficient of sand is gradually decreasing, in which both 1# sand and 2# sand finally return to the initial value, while XZ sand is kept at 2.2 times of initial permeability coefficient. 3) the static loading process of saturated sand under low effective stress is simulated by fully automatic triaxial apparatus. The experimental results show that, The static reloading stress-strain curves of saturated sand under different effective stress states can be divided into three stages: low strength stage. In this paper, the influence of the initial relative compactness of sand, the different liquefaction of sand and the buried depth of soil layer on the development trend of stress-strain curve is also studied in terms of strength recovery stage and strain softening stage. 4) combined with the results of triaxial test and permeation test, the stress state of saturated sand with the ratio of effective stress to initial effective stress is defined as low effective stress state. 5) the research results of seepage and deformation characteristics of soil under low effective stress are integrated into the numerical simulation analysis, and the safety and stability of sandy soil slope under the action of pore water pressure accompanied by percolation of pore water from bottom to top are studied.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU441

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