黄土填方边坡降雨入渗特征及变形破坏模式的模型试验

平山造城、填沟造地等形成大范围近直立的高填方体,这些新型工程为黄土高原带来重要发展机遇的同时,在降雨条件下也将带来前所未有的重大灾变隐患,针对这一状况,开展黄土填方边坡降雨过程中坡体基质吸力、体积含水率、孔隙水压力、湿润锋以及变形等动态响应规律的分析,并对坡体裂缝发育与演化及变形破坏模式进行模型试验研究.结果表明:湿润锋下移致使坡体内部的基质吸力减小而体积含水率和孔隙水压力增加,并且其达到峰值以后稳定,虽然基质吸力降低到最低时,坡体未发生滑塌,但随着雨水的继续入渗,坡体会发生局部和大规模的破坏,表明降雨诱发的黄土滑坡具有一定的滞后性;坡体裂缝体系演化机制为临空面附近产生张拉裂缝且向后扩展-坡体侧翼产生剪张裂缝-后缘产生贯通性的张拉裂缝,形成的拉裂缝不仅提供了优势入渗通道,而且也是每次滑塌的后缘边界;短时连续降雨诱发的填方边坡变形具有浅部间歇性和突发性破坏的特点,导致填方坡体产生多级块体滑动破坏;长时连续降雨诱发的填方边坡变形则具有深部渐变连续性破坏的特点,导致填方坡体产生冲蚀及流滑破坏.

Model Test on Seepage Characteristics and Deformation Failure Modes of Loess Fill Slope Under Rainfall

Cut-and-fill methods in mountain was used to build cities and ditch reclamation land which large-scale and near vertical high-fill slope were formed. While recent developments of the Loess Plateau have provided major opportunities for development, they have also led to the unprecedented risk of major catastrophe during rainfall. The dynamic responses of suction, volumetric moisture content, pore pressure, wetting front, and deformation of loess fill slope were analyzed during rainfall. In particular, the models for the development and evolution of slope cracks, deformation, and slope failure were analyzed. The study shows that during the wetting process, the matrix suction of the slope reduces, and the moisture content and pore water pressure increase till they attain a maximum value, and then they stabilize. Slope failure does not occur when the substrate suction is reduced to the lowest value. However, with the continued infiltration of rainwater, the slope will be damaged locally and on a large-scale, indicating that rainfall-induced loess landslide has a certain lag. The cracks on slopes develop in the following manner. Tensile fractures emerge near the surface of the free face and extend backwards, and then, shear fracture is produced near the slope flanking. The trailing edge produces a tensile crack, which not only provides the advantage of an infiltration channel, but also the trailing edge of each slip. The deformation of the fill slope, induced by short-term continuous rainfall, has the characteristics of intermittent and sudden shallow damages, resulting in multilevel block sliding damage of the fill slope. The deformation of the fill slope, induced by the long-term continuous rainfall, has the characteristics of deep damage gradient continuity, resulting in erosion and slip of the slope.