基于坡面冲刷的荆江典型岸坡稳定性分析

Stability Analysis of Typical Bank Slope Based on Slope Erosion in Jingjiang River

针对荆江典型二元结构的岸坡,采用横向冲刷计算公式探讨了不同水位升降阶段中,水流流速和含沙量对岸坡横向冲刷速率的影响以及岸坡断面形态的变化规律。在此基础上基于饱和-非饱和渗流理论,利用SEEP/w程序建立了二维非稳态渗流模型,模拟了其渗流场在水位升降条件下的变化过程,并基于摩根斯坦法计算分析了在考虑与不考虑坡面冲刷2种条件下岸坡稳定性的变化规律。结果表明:在水位上升期,当不考虑坡面冲刷时,岸坡稳定性是随水位上升而增大的,但当考虑坡面冲刷后,岸坡坡度逐渐增大,岸坡稳定性随水位上升而减小;在水位下降期,岸坡稳定性随水位下降而减小,且考虑坡面冲刷的安全系数下降速率明显大于未考虑冲刷时的情况。因此洪水期与水位下降末期是岸坡失稳的危险期,需重点监控。

According to the features of typical dual soil structure in the Jingjiang River,the calculation formula oftransverse erosion was employed to study the influences of flow velocity and sedimerosion rate of bank slope, as well as the variation law^ of morphologic changes of bank slope under fluctuation of wa-ter level.On the basis of saturated- unsaturated seepage theory, a two-dimensional unsteady seepage model was es-tablished by using SEEP//w program and the change process of seepage field of bank slope was simulated. Further-more, on the basis of calculation of pore-water pressure field,the change law of slope stability in consideration of bank erosion or not was analyzed by using Morgenstem, s method.Results show that when bank erosion is not con-sidered , slope stability increases with the raise of water level and declines with the drawdown of water level; butwhen bank erosion is considered,slope stability decreases both with the raise and the the falling rate of safety factors is obviously larger than that without considering bank flood period and the final stage of water level falling are two dangerous periods of slopmonitored specially.