水分长期入渗诱发黄土滑坡的机理研究

以陕西省洛川县延炼黄土滑坡为例,通过实地调查和现场钻探,发现每年冬季热水管道凝结水的入渗导致了该滑坡的发生,分析探讨了这种长期间断性的水分入渗诱发黄土滑坡的机制。通过的室内试验获得用于斜坡渗流及稳定性分析的物理力学参数,将极限平衡法与有限元法相结合,计算不同渗水阶段斜坡稳定系数。结果表明:随着水分的入渗,非饱和黄土渗透性能的增强,长期间断性渗水过程中引起的斜坡水文响应明显;渗水期间,斜坡土体含水率增大,基质吸力减小,非饱和黄土的抗剪强度降低,局部地下水位上升,进而导致斜坡稳定性降低;停渗期间,土体含水率减小,基质吸力增大,非饱和黄土的抗剪强度升高,地下水位降低,斜坡稳定性升高;数十年的这种间断性渗水过程中,斜坡稳定性呈波动性降低,直至破坏。

Mechanism of Loess Landslide Induced by Long-term Water Infiltration

Taking Yanlian loess landslide in Luochuan County, Shaanxi Province as example, through the field examines and drilling, it has been found that moisture infiltration resulted in the landslide during every winter. This paper discusses its initiation mechanism. For one thing, the laboratory tests are carried out to obtain the parameters for seepage and stability analysis of the slope;for another, combining the limit equilibrium method and the finite element method, the corresponding slope stability factor during the different infiltrate phases is calculated. The results show that the slope has positive hydrological responses during the process of the moisture migration. When moisture infiltrating, the shear strength of unsaturated loess weakens due to the matrix suction decrease. As a result, the stability of the slope decreases and the groundwater table rises. After the moisture infiltration, the shear strength picks up owing to the matrix suction increase. Finally, the stability of the slope increases and the ground water is lowered. Overall, the stability of the slope declines gradually for decades. This phenomenon may also reveal the mechanics of the landslide induced by the long-term low intensity rain.