摘要
三峡工程运用后,上荆江河段河床冲刷较为剧烈,枯水(5 000 m3/s流量)河槽形态相应发生调整,对航运产生了较大影响。本文通过1维水动力学模型确定了各固定断面的枯水河槽形态参数。由于不同断面的河槽形态沿程存在显著差异,故采用基于对数转换的几何平均与断面间距加权平均相结合的河段平均方法,计算了2002—2015年上荆江河段尺度的枯水河槽形态参数。计算结果表明:受大范围护岸及护滩工程的影响,研究时段内上荆江枯水河槽宽度仅有小幅度增加,而相应的水深和面积增加约0.68 m及870 m2,增幅分别达12%及15%,航道条件总体上有所改善;枯水河槽宽深比呈持续减小趋势,由2002年的5.73减小至2015年的5.17,故近期上荆江枯水河槽形态趋于窄深;在火箭洲、沙市及公安弯道等局部河段,江心洲或凸岸边滩的剧烈冲刷导致河槽展宽,宽深比明显增加,引起局部水深不足、航槽不稳定等现象。此外通过分析河槽形态调整对前期水沙条件的滞后响应,建立河段尺度的枯水河槽形态参数与前6年平均汛期水流冲刷强度之间的经验关系。结果表明:受人类活动干扰,上荆江河段尺度的枯水河槽宽度与前期水沙条件的相关程度较低,故建立的枯水河槽宽度公式不能反映水沙条件变化对河宽调整的影响;上荆江河段尺度的枯水河槽水深、面积、宽深比与前6年平均汛期水流冲刷强度的相关程度分别为0.92、0.95及0.85,故这3个参数均可较好地对由于三峡工程运用引起的水沙条件改变做出快速响应。
Significant channel degradation has occurred along the Upper Jingjiang Reach( UJR) because of the operation of the Three Gorges Project( TGP),leading to the corresponding adjustments in low-water channel geometry. The section-scale low-water channel dimensions at each section in the UJR were first calculated by a one-dimensional hydrodynamic model. Due to the remarkable longitudinal variability in cross-sectional geometry,a reach-averaged method was adopted to calculate the reach-scale low-water channel dimensions in this reach annually from 2002 to 2015. Calculation results indicated that:( i) the reach-scale low-water width changed slightly owing to the restriction of various river regulation practices,and the corresponding depth and cross-sectional area increased by 0. 68 m and 870m2,respectively,which led to a continuous decrease in the width-depth ratio from 5. 73 in 2002 to 5. 17 in 2015. Therefore,the low-water channel gradually developed into a narrow and deep shape in the UJR,with the low-water navigation condition being generally improved;( ii) however,the width-depth ratio at low water significantly increased in some sub-reaches such as the site of Huojianzhou,as well as the Shashi and Gongan bends. It was further explained that the central-bar and convex point-bar in these regions underwent dramatic degradation,which finally contributed to deteriorating the navigation condition. In addition,the empirical relationships were developed between the reach-scale low-water channel dimensions and the previous flow and sediment regime. The results showed that( i) the degree of correlation between the reach-scale low-water width and the previous flow and sediment regime was only 0. 37,and thus the developed relationship couldnot be applied to predict the variation in the low-water width;( ii) the reach-scale low-water depth,crosssectional area and width-depth ratio had a close correlation with the flow strength in the past 6 years,with the high correlation degrees of0. 92,0. 95 and 0. 85,respectively. Therefore,these low-water channel dimensions can respond well to the altered flow and sediment regime caused by the TGP operation.
出处
《四川大学学报（工程科学版）》
CSCD
北大核心
2017年第S2期74-82,共9页
Journal of Sichuan University (Engineering Science Edition)
基金
国家自然科学基金资助项目(51579186
51339001)
国家重点研发计划课题资助项目(2016YFC0402303/05)
关键词
枯水河槽
水沙条件
河床调整
航道条件
上荆江
三峡工程
low-water channel geometry
flow and sediment regime
channel adjustments
navigation condition
Upper Jingjiang Reach
Three Gorges Project
