黄土边坡发生失稳破坏作为我国境内发生较多的地质灾害之一，其一旦发生，将造成不可估量的损失。通过统计黄土滑坡的资料可知，当滑坡发生时，大多伴随着降雨的形成。因此研究降雨作用下黄土边坡的破坏机制以及稳定性分析具有重要意义。本文以延安宝塔区某黄土边坡为研究对象，采用理论分析、室内试验以及数值计算相结合的方法分析降雨作用下边坡渗流、变形以及稳定性变化情况，并采取桩-锚联合支护方式对不安全边坡进行加固处理，优化其设计参数。主要研究结果有：

（1）通过饱和-非饱和渗流理论，优化降雨入渗模型Green-Ampt模型，得到湿润峰深度与时间的关系，建立边坡稳定性分析模型。

（2）通过地质勘查得到滑坡的基本特征，分析黄土边坡失稳的影响因素。采集研究区原状土样，利用室内试验滤纸法测定土水特征曲线，确定最适合的土水特征曲线模型为Van Genuchten模型。

（3）利用MIDAS/GTS软件分析不同降雨因素(降雨类型、降雨强度以及降雨持时)下黄土边坡渗流、变形以及稳定性变化情况，结果表明：降雨类型不同时，孔隙水压力均随降雨时间的增加而增大，边坡安全系数随着降雨的持续逐渐减小，且降雨峰值出现的越晚，越不利于边坡的稳定，停雨后，边坡安全系数依然出现缓慢的降低，表明降雨对边坡的影响具有滞后效应；降雨强度不同时，随着降雨强度的持续增强，边坡孔隙水压力增长幅度逐渐增大，雨水入渗范围逐渐扩大，边坡安全系数降低，在停止降雨后，小雨以及中雨工况下，安全系数只有很小幅度的降低，暴雨以及大暴雨工况下下，边坡安全系数出现较大幅度的降低；降雨持时不同时，降雨持续时间的长短与孔隙水压力变化幅度呈正相关，且雨水入渗范围随降雨时间的增大而扩大，降雨初期安全系数降低较快，后期较为缓慢。

（4）采取预应力锚索结合抗滑桩支护形式加固边坡，优化锚索设计参数(预应力大小、锚索布设角度以及锚固段长度)，选取最优加固方案，同时通过模拟计算验证方案的合理性。

As one of the more geological disasters in China, the instability and failure of loess slope will cause immeasurable losses once it occurs. According to the statistical data of loess landslide, when the landslide occurs, it is mostly accompanied by the formation of rainfall. Therefore, it is of great significance to study the failure mechanism and stability analysis of loess slope under rainfall. Taking a loess slope in Baota District of Yan'an as the research object, this paper uses the combination of theoretical analysis, indoor test and numerical calculation to analyze the seepage, adopts the combined support of pile and anchor to reinforce the unsafe slope and optimize its design parameters. The main results are as follows:

(1)Through the saturated unsaturated seepage theory, the rainfall infiltration model Green Ampt model is optimized, the relationship between wetting peak depth and time is obtained, and the slope stability analysis model is established.

(2)The basic characteristics of landslide are obtained through geological exploration, and the influencing factors of loess slope instability are analyzed. The undisturbed soil samples in the study area are collected, and the soil water characteristic curve is measured by indoor test filter paper method. It is determined that the most suitable soil water characteristic curve model is Van Genuchten model.

(3)Using MIDAS/GTS to analyze the changes of seepage, deformation and stability of loess slopes under different rainfall factors (rainfall type, rainfall intensity and rainfall duration), the results show that when the rainfall types are different, the pore water pressure increases with the increase of rainfall time, and the slope safety factor decreases gradually with the continuous rainfall. The later the rainfall peak appears, the more unfavorable to the stability of the slope. After the rain stops, the slope safety factor still decreases slowly, indicating that the impact of rainfall on the slope has a lag effect; When the rainfall intensity is different, with the continuous increase of the rainfall intensity, the increase of the slope pore water pressure gradually increases, the rainwater infiltration range gradually expands, and the slope safety factor decreases. The safety factor has only a small reduction, and the slope safety factor is greatly reduced under heavy rain and heavy rain conditions; When the duration of rainfall is different, the duration of rainfall is positively correlated with the variation range of pore water pressure, and the range of rainwater infiltration expands with the increase of rainfall time. The safety factor decreases rapidly in the initial stage of rainfall and slowly in the later stage.

(4)Adopt the form of prestressed anchor cable combined with anti slide pile support to strengthen the slope, optimize the anchor cable design parameters (prestress size, anchor cable layout angle and anchor section length), select the optimal reinforcement scheme, and verify the rationality of the scheme through simulation calculation.

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