中文摘要：

针对渐进坍塌型崩岸，从土力学和河流动力学两方面理论出发，建立了岸坡稳定的力学模式，结合室内概化模拟试验和数值计算，分析了岸坡稳定或破坏的力学机制，揭示了缓坡出现崩岸的原因。结果表明，岸坡坡脚未受水流冲失时，若坡内渗流出逸坡降小于渗透破坏的临界坡降，岸坡处于稳定状态，当坡脚被水流冲失后，渗流渗径缩短，水土结合处坡面出逸坡降增大，大于临界坡降时则出现渗透破坏，引起局部小幅度土体崩塌，其后部土体失去支撑而陆续产生失稳破坏，随着时间的延长，土体崩塌现象逐步向后发展，最终导致岸坡整体崩塌破坏。

英文摘要：

In view of the gradual riverbank collapse, a hydrodynamic model for assessing riverbank stability is established on the base of soil mechanics and river dynamics theory. Combined with generalized model tests and numerical calculation, the mechanism of riverbank stability is analyzed, and the failure reason for slight slopes is explained. Re- suits show that the slope should be stable when the seepage exit gradient on the slope surface is less than the critical gradient of infiltration failure. After the toe of the slope was washed away by current, partial infiltration failures on the slope begin to appear and will develop with the increase of the seepage exit gradient due to the shortening in seepage path length. The back soil mass will fail successively due to lack of support. The gradual soil mass failure will develop backward with time leading to the collapse and destruction of the entire slope eventually.