降雨条件下土体潜蚀机制及诱发滑坡研究

发布时间：2018-05-17 06:21

本文选题：降雨 + 边坡稳定性　；参考：《上海交通大学》2015年硕士论文

【摘要】：滑坡是一种具有突发性和灾难性的地质灾害,降雨是诱发滑坡灾害的主要原因。天然斜坡在沉积、风化等作用下呈现粗细夹杂的地层条件,具有显著的空间变异特性。在降雨入渗作用下土坡内细颗粒会随渗流发生运移产生潜蚀作用。因此,揭示降雨作用下土体潜蚀机制,研究渗流潜蚀对土坡稳定性的影响规律,具有重要的理论意义和工程实践价值。本文以无限边坡为研究对象,基于多孔介质动力学和非饱和土力学理论,采用数值分析的方法,进行了有限元模拟分析,探讨了潜蚀作用对雨水入渗和边坡稳定性的影响规律。主要研究内容和成果如下:1.通过联立颗粒运移方程与非饱和土渗流方程,结合非饱和土水力特性方程、土体潜蚀本构关系以及土壤转换函数,建立了渗流潜蚀耦合的边坡稳定性分析模型。2.利用COMSOL软件建立均质无限边坡有限元模型,对强降雨条件下边坡土体内细颗粒运移和潜蚀进行了模拟,研究了渗流潜蚀对孔压分布和边坡稳定性的影响,探讨了饱和渗透系数、进气值和潜蚀本构模型参数对渗流潜蚀的影响。结果表明:潜蚀主要发生在湿润锋范围内浅层土体,潜蚀加速了湿润锋下行速度,进一步降低边坡稳定性;饱和渗透系数、进气值是影响渗流潜蚀作用的主要因素;当降雨入渗强度大于饱和渗透系数时,饱和渗透系数越大,潜蚀对入渗和边坡稳定性的影响越显著;进气值越小,潜蚀作用对入渗和边坡稳定性的影响越显著。3.对四种不同颗粒成分土坡算例进行了渗流潜蚀模拟,引入基于非饱和土特性参数的土壤转换函数,考虑渗流潜蚀过程中颗粒成分动态变化的影响,分析了不同颗粒成分情况下,潜蚀作用对降雨入渗和边坡稳定性的影响规律。结果表明,当细颗粒含量大于30%的情况下,潜蚀作用对渗流和边坡稳定影响不明显;细颗粒含量小于30%的情况下,渗流潜蚀对边坡的稳定性有显著的影响。4.采用随机场模拟土的空间变异性,对土性参数进行离散化,生成空间各点土性参数样本。对不同类型非均质性土坡的渗流潜蚀进行了有限元分析模拟,揭示了非均匀性对潜蚀发展过程及局部和整体稳定性的影响规律。5.对试验配备的土样进行了土柱渗流潜蚀试验研究,观察潜蚀现象的发生,分析了土体渗流潜蚀的发展规律。观测结果表明:渗流速度与细颗粒流失累计量成非线性关系,随着渗流速度的增大,细颗粒会持续流出,但是流出量逐渐减小;累计流失质量是增加的,但其增加速率逐渐减小。
[Abstract]:Landslide is a sudden and catastrophic geological disaster, and rainfall is the main cause of landslide disaster. The natural slopes show thick and fine stratigraphic conditions under the action of sedimentation and weathering, and have remarkable spatial variation characteristics. Under the effect of rainfall infiltration, the fine particles in the soil slope will move with the seepage to produce the latent erosion. Therefore, it is of great theoretical significance and practical value to reveal the underlying erosion mechanism of soil under rainfall and to study the influence of seepage erosion on the stability of soil slope. Based on the dynamics of porous media and the theory of unsaturated soil mechanics, finite element simulation analysis of infinite slope is carried out by means of numerical analysis, and the influence of latent erosion on Rain Water infiltration and slope stability is discussed in this paper. The main research contents and results are as follows: 1. Through simultaneous particle transport equation and unsaturated soil seepage equation, combined with unsaturated soil hydraulic characteristic equation, soil latent erosion constitutive relation and soil transformation function, the slope stability analysis model of seepage and erosion coupling is established. The finite element model of homogeneous infinite slope is established by using COMSOL software. The fine particle migration and subsurface erosion in slope soil under heavy rainfall are simulated. The influence of seepage erosion on pore pressure distribution and slope stability is studied, and the saturated permeability coefficient is discussed. The influence of intake value and constitutive model parameters of latent erosion on seepage erosion. The results show that the subsurface erosion mainly occurs in shallow soil within the range of the wetting front, which accelerates the downward velocity of the wetting front and further reduces the slope stability, the saturation permeability coefficient and the intake value are the main factors affecting the seepage potential erosion. When the rainfall infiltration intensity is greater than the saturation permeability coefficient, the larger the saturation permeability coefficient, the more significant the influence of the latent erosion on the infiltration and slope stability, and the smaller the intake value, the more significant the influence of the latent erosion on the infiltration and slope stability. In this paper, four examples of soil slope with different particle composition are simulated. The soil transformation function based on the characteristic parameters of unsaturated soil is introduced, and the influence of the dynamic change of particle composition in the process of seepage erosion is considered, and the different particle composition is analyzed. The influence of latent erosion on rainfall infiltration and slope stability. The results show that when the content of fine particles is more than 30%, the effect of subsurface erosion on the seepage flow and slope stability is not obvious, and when the content of fine particles is less than 30%, the seepage erosion has a significant effect on the slope stability. The random field simulation of soil spatial variability is used to discretize soil parameters and to generate samples of soil parameters at various points in space. The seepage potential erosion of different types of heterogeneous soil slopes was simulated by finite element analysis, and the influence of heterogeneity on the development process and local and global stability of subsurface erosion was revealed. The experimental study of soil column seepage latent erosion was carried out on the soil samples, the occurrence of latent erosion phenomenon was observed, and the development law of soil seepage latent erosion was analyzed. The results show that the seepage velocity has a nonlinear relationship with the cumulative loss of fine particles. With the increase of the seepage velocity, the fine particles will continue to flow out, but the outflow volume will gradually decrease, and the cumulative loss mass will increase. But its increasing rate gradually decreased.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P642.22

【参考文献】