上荆江河岸崩退过程的概化模拟  

Conceptual model of bank retreat processes in the Upper Jingjiang Reach

作　　者：邓珊珊[1] 夏军强[1] 周美蓉[1] 李洁[1] 

机构地区：[1]武汉大学水资源与水电工程科学国家重点实验室,武汉430072

出　　处：《科学通报》2016年第33期3606-3615,共10页Chinese Science Bulletin

基　　金：国家自然科学基金(51579186;51339001);国家重点研发计划(2016YFC0402303)资助

摘　　要：崩岸是上荆江河段河床变形过程的一个重要方面,它与近岸水流冲刷及河岸土体特性等因素密切相关.三峡工程运用后该河段河床冲刷下切显著,导致局部河段的崩岸现象较为突出.本文改进了河岸崩退过程的概化模型,耦合了坡脚冲刷、潜水位变化及河岸稳定性计算模块,并在稳定性分析中考虑了侧向水压力、孔隙水压力及非饱和土体基质吸力的作用.采用该模型计算了2005年上荆江典型断面(荆34和荆55)的崩岸过程,计算结果表明:这两个断面的河岸分别发生6次和4次崩塌,且多发生于洪峰期和退水期;总崩退宽度为27和20 m,且计算与实测的岸坡形态较为符合.最后开展了相关河岸土体参数的敏感性数值试验,分析了土体物理力学特性变化对崩岸过程的影响:河岸崩退次数、宽度总体上随土体抗剪强度及渗透系数的增大而减小,前者基本呈单向变化,而后者还与崩塌时坡脚的冲刷幅度有关;此外潜水位滞后于河道水位的变化特点,降低了退水期的河岸稳定性.Bank retreat is always an important part of channel evolution in the Upper Jingjiang Reach（UJR）, which usually occurs due to a combination of bank-toe erosion caused by fluvial action and mass failure affected by non-fluvial factors, covering the variations in bank soil properties, in-channel water level and ground water level. After the operation of the Three Gorges Project, the variation in the flow and sediment regime, especially the dramatic reduction in sediment load, has caused significant channel degradation in the UJR, further leading to a higher frequency of bank retreat processes. In this study, an improved conceptual model for predicting the process of bank retreat was thus proposed, consisting of three submodules to simulate the processes of bank-toe erosion, mass failure and groundwater level variation, with the terms of hydrostatic confining pressure, pore water pressure and matrix suction of unsaturated soil being considered in the submodule of bank stability analysis. The proposed model was applied to simulate the bank retreat processes at two typical sections of Jing34 and Jing55 in the UJR in 2005. The results indicate that：（1） changes in ground water level lagged behind that in in-channel water level, with an obvious delayed time of 3–4 days being identified between the occurrence of peak values during the rising period at Jing55;（2） six and four bank collapses occurred at these two sections, respectively, with the calculated retreat widths of 27 m and 20 m, which were in close agreement with the measured data as well as the calculated bank profiles; and（3） a higher occurrence frequency of bank failure was identified during the flood peak and recession stages, due to intensive bank-toe erosion and high ground water level, while the failed soil-block volume was larger during the rising and flood-peak periods, affected by the bank-toe erosion degree at failure. Then, effects on the bank retreat were investigated of bank soil properties and delayed ground water level variation.

关 键 词：河道崩岸 河岸土体特性 水流冲刷 潜水位 概化模型 上荆江 

分 类 号：TV147[水利工程—水力学及河流动力学]