降雨诱发非饱和残积土滑坡研究

发布时间：2018-04-08 23:19

本文选题：降雨　切入点：残积土边坡　出处：《福州大学》2014年硕士论文

【摘要】：在我国东南沿海地区,广泛分布着非饱和残积土。由于建设需要,常常开挖山体,从而形成高陡边坡。边坡地下水位埋藏较深,在地下水位以上形成非饱和区,当受到持续的降雨入渗作用时,非饱和区土体含水量增加,吸力减小,甚至在局部形成暂态饱和区和暂时的附加孔隙水压力,从而诱发滑坡。因此,研究此类边坡在降雨下的渗流及其稳定性变化规律具有重要意义。论文以一典型的非饱和残积土边坡为研究对象,通过现场土样采集、室内测试、理论分析、以及有限元数值计算,开展降雨条件下非饱和残积土边坡渗流及其稳定性研究。获得的主要成果有：(1)采用压力板仪测试了吸湿过程残积土的土水特征曲线,结合Van Genuchten模型获得了吸湿过程中体积含水率和基质吸力关系的表达式,作为预测渗透性函数和稳定性计算的基础。(2)利用自行改装的渗气装置测试了残积土在不同体积含水率下的渗气系数,以分析气相流对边坡渗流及稳定性的影响；发现考虑气相流动的边坡内能够积聚气体从而形成一定的孔隙气压力,虽然减少了降雨的入渗,但也降低了边坡的安全系数。(3)借助于组装的蒸发模型,预设一恒定的环境条件,研究残积土试样在此环境中的蒸发规律,并以此探讨降雨前后蒸发作用对边坡稳定性的影响；蒸发作用使边坡趋于干燥,安全系数提高。(4)通过室内环刀法测试了残积土的田间持水量,确定了边坡稳定性数值计算中选用的初始孔隙水压力分布状态；初始状态较湿润的边坡在相同的降雨过程始终保持着较高的孔隙水压力,稳定性也较差。(5)利用慢剪试验获得了土样的有效抗剪强度参数,根据土水特征曲线预测了吸力内摩擦角的变化,从而得到非饱和土的抗剪强度表达式。(6)在试验的基础上,应用二维饱和-非饱和渗流有限元软件分析了降雨时不同雨强、不同初始状态、是否考虑气相流和是否考虑蒸发作用的工况下边坡渗流场的变化规律,最后,利用极限平衡条分法计算了相应的安全系数。(7)小雨强长历时的降雨对边坡稳定性影响最大,通常滑坡的发生是短期内多次降雨综合作用的结果。论文从多个角度进行了降雨下非饱和残积土滑坡研究,成果对进一步揭示残积土的工程特性、分析残积土坡失稳机制具有重要的理论及实际意义。
[Abstract]:Unsaturated residual soil is widely distributed in southeast coastal areas of China.Because of the need of construction, the mountain is often excavated to form a high-steep slope.The underground water level of the slope is deep and the unsaturated area is formed above the groundwater level. When the soil is subjected to the effect of continuous rainfall infiltration, the soil moisture content increases and the suction decreases in the unsaturated area.Even local transient saturation zone and temporary additional pore water pressure are formed, which induce landslide.Therefore, it is of great significance to study the seepage and stability of such slope under rainfall.Taking a typical unsaturated residual soil slope as an object of study, the seepage and stability of unsaturated residual soil slope under rainfall conditions are studied through field soil sample collection, laboratory test, theoretical analysis and finite element numerical calculation.The main results obtained are as follows: (1) the soil-water characteristic curves of residual soil in the process of moisture absorption are measured by pressure plate instrument, and the expression of the relationship between volume moisture content and the suction of matrix in the process of moisture absorption is obtained by using Van Genuchten model.As the basis of predicting permeability function and stability calculation, the permeability coefficient of residual soil under different volume water content was tested by using self-modified seepage device to analyze the influence of gas flow on slope seepage and stability.It is found that gas can be accumulated in the slope considering gas flow to form a certain pore gas pressure, although the infiltration of rainfall is reduced, but the safety factor of slope is also reduced.) by means of the assembled evaporation model, a constant environmental condition is preset.The evaporation law of residual soil samples in this environment is studied, and the influence of evaporation on slope stability before and after rainfall is discussed.The field water holding capacity of residual soil was measured by means of indoor annular knife method, and the initial pore water pressure distribution state was determined in the numerical calculation of slope stability.The slope with wetter initial state always maintains high pore water pressure in the same rainfall process, and the stability is also poor. 5) the effective shear strength parameters of soil samples are obtained by slow shear test.According to the characteristic curve of soil and water, the variation of internal friction angle of suction is predicted, and the expression of shear strength of unsaturated soil is obtained.Different initial states, whether to consider the gas flow and whether to consider the evaporative effect of the conditions of slope seepage field changes, finally,The limit equilibrium strip method is used to calculate the corresponding safety factor. 7) rainfall with long duration of light rain has the greatest influence on slope stability. Usually the occurrence of landslide is the result of multiple rainfall in a short period of time.In this paper, the landslide of unsaturated residual soil under rainfall is studied from many angles. The results have important theoretical and practical significance for further revealing the engineering characteristics of residual soil and analyzing the mechanism of slope instability.
【学位授予单位】：福州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU43;P642.22

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