河岸崩塌类型与崩塌模式的研究

Study of types and collapse modes of bank failures

崩岸是河流侧向演变的重要形式,包括滑崩、挫崩、落崩、窝崩等。滑崩一般发生于土质均匀和松散的岸滩,其崩塌过程较长,崩塌破坏面一般为曲面,可采用土力学中的条分法进行分析;挫崩主要发生在具有纵向裂隙的黏性岸滩,其崩塌过程较简单和短暂,崩塌破坏面为平面,可采用崩体力学平衡分析;在黏性岸滩的岸脚遭受水流淘刷,上部块体处于临空状态下发生落崩,崩塌破坏面为平面,其崩塌过程简单和短暂,分为剪切、旋转(倒崩)和拉伸三种落崩模式,落崩仍可按崩体力学平衡法进行分析;对于特定的河岸边界条件,当受到水流的剧烈淘刷或土体失去承载能力时,河岸可能发生窝崩,其崩塌过程连续复杂,可分为淘刷窝崩和液化窝崩。通过引入岸滩边坡形态坡度,分析了边坡形态坡度与稳定性的关系,指出岸滩崩塌坡度大于稳定坡度,岸滩边坡坡度介于崩塌坡度和稳定坡度之间,岸滩处于不稳定状态。

The bank failure is an important type of lateral river process and can be divided into sliding failure, sinking failure, falling failure, and ~ failure, etc. The sliding failure generally occurs on the bank with the well-distributed and loose soil. The sliding collapse takes long process with a collapse curve, and it can be analyzed with slice division methods. The sinking failure generally occurs on viscous banks with lengthwise cracks. Its collapse takes simple and short process with a plane. The lateral caving erosion at the bottom of the bank results in the upper part suspended and the falling failure will occur with a plane, which divided into shear, toppling and stress failures. The sinking failure and the falling failure can be analyzed with a force balance method. The ~ failures result from the strong caving-in or the soil liquefaction of the bank for the spe- cific soil bank with a continuous and complex collapsed process, and divides into the ~ caving failure and the f~ liquefaction failure. Using a slope form parameter of bank, the relationship between the slope form parame- ter and bank stability is analyzed. It is pointed out that the critical slope of bank failure is much greater than the stable critical slope, and the bank is in unstable state when the slope form parameter is between the critical slope of bank failure and the stable critical slope.