ISSN 1000-3665 CN 11-2202/P

    三峡库区典型逆向岩质岸坡塌岸-滑坡破坏机理研究

    Bank collapse-landslide failure mechanism of typical reverse rock bank slope in Three Gorges Reservoir area

    • 摘要: 现阶段大多数逆向岩质岸坡倾倒失稳破坏均被解释为受倾角和结构面控制的渐进式整体失稳破坏机制,但据调查表明一些库区逆向岸坡倾倒变形加剧或失稳前,都普遍存在前缘塌岸现象。为深入研究塌岸约束条件下塌岸-滑坡破坏机制及其灾变过程,本研究以三峡库区巫峡段龚家坊滑坡为例构建二维物理模型进行试验,开展典型逆向岩质岸坡在库水位侵蚀下发生塌岸-滑坡破坏机理研究。研究结果表明:(1)在滑坡失稳演化过程中塌岸改变了坡形、坡体结构、应力分布,并且为上部变形体提供了重要临空条件,是逆向岩质岸坡滑坡破坏的灾变加速诱因;(2)形成滑坡的主要原因在于反倾岩层重力时效的累计下弯曲倾倒产生大量拉张裂隙,蓄水后纵横两向裂隙逐渐在塌岸的影响下产出并贯通形成多级滑面;(3)塌岸-滑坡链式演化过程中,塌岸发生前岸坡各点的应力、位移均无明显波动,塌岸发生后坡内应力集中现象明显,坡表变形,破裂面逐步贯通;(4)不同深度的坡脚侵蚀区在塌岸-滑坡演化过程中失稳坡体均有明显的分级滑移现象,滑移前,侵蚀区顶部岩梁在上覆荷载的挤压下岩层层理面累计弯曲角度达到15°~23°时,斜坡后缘卸荷裂缝发育,进一步贯通形成深度约为侵蚀区深度2.5~3倍的滑面;(5)滑坡破坏规模与坡脚侵蚀深度正相关,坡脚侵蚀深度深,塌岸出现越早,形成潜在破坏区范围越大,岩层变形破坏过程中弯曲滑移现象越明显。相关成果可为库区逆向岩质岸坡倾倒破坏机制的研究提供新视野,为库区类似岸坡的防治工作提供理论依据。

       

      Abstract: At present, most of the reverse rock slope toppling instability failure is interpreted as a progressive overall instability failure controlled by dip angle and structural plane. However, the phenomenon of leading edge collapse is common in some reservoir areas before the toppling deformation of reverse rock slope is intensified or destabilized. To further analyze the failure mechanism and disaster process of bank collapse-landslide under the constraint condition of bank collapse, this study constructed a two-dimensional model of Gongjiafang landslide in Wuxia section of Three Gorges Reservoir area to analyze the failure mechanism of bank collapse-landslide of typical reverse rock bank slope under the erosion of reservoir water level. The results show that in the process of landslide instability evolution, the bank collapse changes the slope shape, slope structure, and stress distribution. It provides important free-face conditions for the upper deformation body, which is the disaster acceleration inducement of reverse rock slope landslide failure. The main reason for the formation of landslide is that a large number of tensile cracks are produced by the cumulative bending and toppling of the anti-dip rock strata. After impoundment, the vertical and horizontal cracks are gradually produced under the influence of bank collapse and form a multi-stage sliding surface. In the process of bank collapse-landslide chain evolution, the stress and displacement of each point of the bank slope before the bank collapse did not fluctuate significantly. After the bank collapse, the stress concentration in the slope was significant with deformed slope surface, and the fracture surface was gradually penetrated. The slope toe erosion area at different depths has obvious graded slip phenomenon in the process of bank collapse-landslide evolution. Before slip, when the cumulative bending angle of the bedding plane of the rock beam at the top of the erosion area reaches 15°~23° under the extrusion of the overlying load, the unloading cracks at the trailing edge of the slope develop, and further penetrate to form a sliding surface with a depth of about 2.5~3 times deeper than that of the erosion area. The scale of landslide failure is positively correlated with the erosion depth of slope toe. The deeper the erosion depth of slope toe is, the earlier the collapse occurs, the larger the range of potential failure zone is, and the more obvious the bending slip phenomenon is in the process of rock deformation and failure. This study can provide new insight into the study on the toppling failure mechanism of the reverse rock bank slope and a theoretical basis for the prevention and control of similar bank slopes in the reservoir area.

       

    /

    返回文章
    返回