黄土边坡在降雨条件下的雨水入渗机理、力学特性研究和边坡稳定性评价对于降低滑坡等自然灾害发生的风险，保护黄土地区较为脆弱的生态环境，减少经济损失具有重要作用。以西安地区为研究背景，通过理论分析、室内试验和数值模拟相结合的方法，评价黄土边坡的稳定性，主要的研究成果如下：

通过分析降雨条件下黄土边坡的雨水渗流特点，建立降雨条件下黄土边坡物理模型，构建了考虑降雨时长、降雨强度、坡角和任意深度处的瞬态含水率表达式，探索了降雨条件下黄土边坡的入渗规律。

完成了非饱和黄土的三轴剪切试验，在试样含水率不断增加的过程中，土体的粘聚力会逐渐降低，内摩擦角也会降低，但是降低的速率要比粘聚力降低的速率要小。对于非饱和黄土，基质吸力和围压的变化，会引起强度的变化，随着基质吸力的不断增大，其粘聚力不断增大，内摩擦角变化不大，但是内摩擦角的度数是在缓慢变大的，表明基质吸力的变化对黄土内摩擦角的影响较小。将试验结果进行拟合，得出了随着基质吸力变化而变化的φ^b的表达式以及非饱和有效应力公式中参数的表达式。

通过使用压力板仪进行了土水特征曲线试验，研究分析了非饱和黄土的土水特性，将渗流场与应力场进行了耦合。在土水特征曲线的一整个减湿增湿的过程中，不同过程中的体积含水量与基质吸力之间不是完全对应的关系，存在一定的偏差，相同基质吸力下，在减湿的过程中体积含水率会高于增湿过程中的体积含水率，这个现象和土体的孔隙大小、空间骨架结构有关。通过拟合，得到了VG模型的相应的参数，在减湿过程中α=0.30325，q=2.0，R²=0.98823；在增湿的过程中，α=0.11773，q=2.43843，R²=0.98198。

基于渗流场与应力场的耦合，通过降雨强度、降雨历时、坡角等参数，采用边坡稳定性分析的条分法，得到降雨条件下黄土边坡的安全系数计算表达式，建立降雨条件下黄土边坡稳定性分析模型，探究边坡的失稳机理，评价降雨条件下黄土边坡的稳定性。

（5）基于GTS/NS有限元数值模拟软件，通过Galerkin方法构建起计算边坡稳定性的有限元方程。根据试验所得的数据建立起降雨条件下二维边坡的有限元分析模型，考虑坡角、坡高、降雨强度、降雨时长的因素，对每一种因素建立不同的分析工况，具体如下：坡角选择20°、30°、45°、60°、80°五种；坡高选择10m、15m、20m、25m、30m五种；降雨强度选择10mm/d、35mm/d、50mm/d、65mm/d、80mm/d，降雨时长选择0.5d、1d、1.5d、2d、3d。对于坡角、坡高、降雨强度来说，当它们都变大时，边坡的安全系数是逐渐减小的，但是坡角和坡高的变化所引起的安全系数的变化值要大于降雨强度的影响；对于降雨时长，在整个下雨的过程中，随着雨水的渗入，边坡的安全系数是逐渐减小的，减小值变化的幅度很小。  

The study of rainfall infiltration mechanism, mechanical properties and slope stability evaluation of loess slope under rainfall conditions plays an important role in reducing the risk of landslide and other natural disasters, protecting the fragile ecological environment and reducing economic losses. Taking Xi'an area as the research background, the stability of loess slope is evaluated by combining theoretical analysis, laboratory test and numerical simulation.The main research results are as follows:

(1) Based on the analysis of rainfall seepage characteristics of loess slope under rainfall condition, the physical model of loess slope under rainfall condition is established, and the transient water content expression considering rainfall duration, rainfall intensity, slope angle and arbitrary depth is constructed, and the infiltration law of loess slope under rainfall condition is explored.

(2) The triaxial shear test of unsaturated loess is completed. In the process of increasing the moisture content of the sample, the cohesion of the soil will gradually decrease, and the internal friction angle will also decrease, but the decreasing rate is smaller than that of the cohesion. For unsaturated loess, the change of matric suction and confining pressure will cause the change of strength. the degree of internal friction angle increases slowly, which indicates that the change of matric suction has little effect on the internal friction angle of loess. By fitting the experimental results, the relationship between the change of matric suction and the change of matric suction was obtainedφ^b .The expression of  of parameters in the unsaturated effective stress formula.

(3) The soil water characteristics of unsaturated loess are studied through the soil water characteristic curve test with pressure plate apparatus. In the whole process of soil water characteristic curve dehumidification and humidification, the relationship between volume water content and matric suction in different processes is not completely corresponding, and there is a certain deviation. Under the same matric suction, the volume water content in the process of dehumidification will be higher than that in the process of humidification, which is related to the pore size and spatial skeleton structure of soil. The experimental data are input into origin for fitting, and the corresponding parameters of VG model are obtained α=0.30325，q=2.0，R²=0.98823；In the process of humidification, α=0.11773，q=2.43843，R²=0.98198。

(4) Based on the coupling of seepage field and stress field, through the rainfall intensity, rainfall duration, slope angle and other parameters, the slice method of slope stability analysis is adopted to obtain the calculation expression of safety factor of loess slope under rainfall conditions, establish the stability analysis model of loess slope under rainfall conditions, explore the instability mechanism of slope, and evaluate the stability of loess slope under rainfall conditions.

(5) Based on GTS / NS finite element numerical simulation software, the finite element equation of slope stability is established by Galerkin method. According to the experimental data, the finite element analysis model of two-dimensional slope under rainfall condition is established. Considering the factors of slope angle, slope height, rainfall intensity and rainfall duration, different analysis conditions are established for each factor. The details are as follows: slope angle selection is 20°、30°、45°、60°、80°; The slope height is 10 m, 15 m, 20 m, 25 m and 30 m; The rainfall intensity is 10 mm / d, 35 mm / d, 50 mm / d, 65 mm / d and 80 mm / d, and the rainfall duration is 0.5 d, 1 d, 1.5 d, 2 d and 3 d. For slope angle, slope height and rainfall intensity, when they all increase, the safety factor of slope decreases gradually, but the change value of safety factor caused by the change of slope angle and slope height is greater than that of rainfall intensity; For the duration of rainfall, in the whole process of rainfall, with the infiltration of rainwater, the safety factor of the slope is gradually reduced, and the decreasing range is very small. 

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