持续降雨入渗对黄土边坡稳定性的影响

Study on the Influence of Continuous Rainfall Infiltration on the Loess Slope Stability

为探索黄土边坡在持续降雨条件下的入渗规律及其对边坡稳定性的影响,采集陕北治沟造地工程中开挖边坡的土样,在室内模拟土体垂直方向一维降雨积水入渗过程,观测分析土体含水率的变化和湿润锋运移特征,研究含水率变化对边坡土体抗剪强度的影响。根据降雨积水入渗试验得到的不同时刻土体饱和区分布情况,结合饱和区土体重度、黏聚力、内摩擦角的具体数值,采用FLAC3D岩土工程数值计算软件分析了持续降雨条件下边坡的安全稳定性以及潜在滑动面的变化情况。研究结果表明:在降雨积水入渗条件下,浅层土体中湿润锋运移速度较快,随着深度增大,湿润锋运移速度逐渐减缓;当湿润锋到达时,不同深度土体含水率均呈现先陡升再趋于平缓上升的变化规律,土体的饱和度可达到80%。降雨入渗使土体的抗剪强度显著降低,随着降雨历时的增加,边坡土体中的饱和区域增大,土体局部的剪切变形增大,进而局部发生塑性变形逐步扩展形成剪切带,从而导致滑坡。因此,黄土边坡应设置排水措施,避免降雨入渗引发滑坡等自然灾害。

In order to explore the mechanism of continuous rainfall infiltration in loess soil and its influence on the loess slope stability,soil samples were collected on the excavated loess slope in the engineering of land reclamation in loess hilly and gully region in Northern Shaanxi.The laboratory tests were conducted to simulate the vertical one-dimensional continuous rainfall infiltration process,the change of soil moisture content and the characteristics of wetting front movement were observed and tested,and the effect of moisture content on shear strength of slope soil was analyzed by direct shear test. According to the distribution of soil saturation area at different time points obtained from the rainfall infiltration test and the specific values of unit weight,cohesion and internal friction angle in saturated zone,the changes of potential sliding surface and the stability of slope under continuous rainfall infiltration conditions were calculated and analyzed by FLAC3D software. The results show that the wetting front moves faster in the shallow soil under the condition of rainfall infiltration,and the velocity of the wetting front gradually decreases with the depth increasing. When the wetting front arrives,the water content of the soils at different depths shows a first steep rise and then a gradual increase,and the soil saturation can reach 80%. The rainfall infiltration reduces the shear strength of the soil,and with the increase of the rainfall duration,the saturated area in the slope soil increases,and the deformation of some parts in slope soil increase,and then the deformation of those parts gradually expands to form a shear band,resulting in landslides. Therefore,the loess slope should be set drainage measures to avoid landslides caused by rainfall infiltration and other natural disasters.