针对当前三峡工程运用后坝下游河床的调整特点,将床面冲淤与河岸崩退的计算模块相结合,构建了基于断面尺度的河床纵向及横向变形的概化数学模型。以上荆江荆34断面为研究对象,采用概化模型计算了该断面2006年和2008年水文年的河床纵向与横向变形过程,计算的河床纵向冲刷量、河岸崩退总宽度及崩塌后岸坡形态等结果与实测结果吻合较好。此外还分析了考虑与不考虑床面冲淤2种情况下2006年荆34断面形态调整的计算结果,该断面河床冲刷主要集中在枯水河槽,床面冲刷下切导致河岸高度增大,最大增幅约1.9 m,且考虑河床冲淤后计算的河岸崩退总宽度比不考虑时的计算值偏大20%。表明了近岸床面冲刷下切导致滩槽高差增大,将会加剧崩岸的发生。

According to the adjustment characteristics of the downstream riverbed of dam after the operation of the Three Gorges Project, we developed a generalized mathematic model for predicting the longitudinal and lateral deformation of riverbed. The computational module of bed evolution is combined with that of bank retreat in this model. Taking cross-section Jing34 in the Upper Jingjiang Reach as a study object, we calculated the longitudinal and lateral deformation processes during the 2006 and 2008 hydrological years by using the generalized model. The predicated erosion volume of the riverbed, total bank retreat width and the failed bank profile were all in good agreement with the measured data. In addition, the effect of the riverbed evolution on the bank profile of cross-section Jing34 in 2006 was also investigated. Simulated results indicate that the position of river bed scouring is mainly concentrated in the low flow channel, and the maximum increase in height of river bank is about 1.9m induced by the river bed erosion. Moreover, the calculated total bank retreat width under the scenario with bed evolution is 20% greater than that under the scenario without bed evolution. Therefore, the bed evolution increases the relative bank height, which can reduce the safety factor of bank.