强降雨作用下黄土-泥岩接触面滑坡模型试验及稳定性研究

Model tests and stability analysis of loess-mudstoneinterface landslides under heavy rainfall

摘要:

为探究黄土-泥岩接触面滑坡在强降雨作用下的破坏特征并对其进行稳定性评价,以甘肃省陇南市徽县某滑坡为依托,采用物理模型试验、有限元数值模拟及理论分析的手段,揭示黄土-泥岩接触面滑坡的变形破坏特征，并改进理论分析计算方法。研究表明:(1)在持续性强降雨作用下,黄土与泥岩交界面附近土体一直处于饱和状态,黄土-泥岩接触面滑坡的主要变形过程为滑移拉裂,坡体的破坏模式为牵引-推移复合式;(2)滑坡稳定性随着降雨强度的增加逐渐降低,通过多组滑坡模型试验,得到不同降雨强度下滑坡启动时间,发现降雨强度与滑坡启动时间呈对数关系;(3)通过模拟滑坡位移变化,发现黄土-泥岩接触面处孔隙水压力最高并向周围不断扩散降低,符合黄土-泥岩接触面滑坡实际入渗特征,验证了滑坡模型试验所得结论的准确性;(4)基于传统的不平衡推力法,考虑降雨入渗所产生渗透力的影响,改进稳定性计算方法,并对滑坡稳定性进行评估,结果显示滑坡稳定性系数明显低于规范所求,表明坡体从降雨开始至发生失稳所需时间明显小于常规预测值。研究结论可以为滑坡灾害的研究与防治提供重要依据。

Abstract:

In this study, the failure characteristics of loess-mudstone interface landslides under heavy rainfall were investigated, and their stability was evaluated. In particular, physical model tests, finite element numerical simulation, and theoretical analysis were conducted to reveal the deformation and failure characteristics of loess-mudstone interface landslides and improve the theoretical analysis and calculation methods, taking a landslide incident that occurred in Hui County, Longnan City, Gansu Province, as a case study. Several results were obtained. (1) Under the action of continuous heavy rainfall, the soil near the loess-mudstone interface is always in a saturated state. The main deformation process of loess-mudstone interface landslide is sliding-crack, with a composite failure mode of traction-push. (2) Landslide stability gradually decreases with the increase in rainfall intensity. After conducting multiple sets of landslide model tests to determine the landslide initiation times under different rainfall intensities, the results reveal that rainfall intensity and the landslide initiation time are logarithmically related. (3) Upon simulating the displacement changes of loess-mudstone interface landslide, it is revealed that the pore water pressure at the interface between loess and mudstone is the highest and gradually diffuses and decreases. This result is consistent with the actual infiltration characteristics of loess-mudstone interface landslides, thus verifying the accuracy of the conclusions obtained from the landslide model test. (4) Based on the traditional unbalanced thrust force method, the stability calculation method is improved, and the landslide stability is evaluated considering the influence of the seepage force generated by rainfall infiltration. The results indicate that the landslide stability coefficient is significantly lower than that required by the code, indicating that the time from the beginning of rainfall to slope instability is shorter than the conventional prediction value. The research conclusions provide an important basis for the research and prevention of landslide disasters.