新开航槽对山区弯曲分汊河道水沙输移的影响

Effect of newly-developed channel on water and sediment transport in curved and branched rivers in mountainous areas

长江上游渣角河段是典型的分汊河段,具有弯、浅、险、急的枯水碍航特性。基于渣角滩的碍航特性,提出了两汊通航的航道整治方案。采用物理模型试验与二维水沙数值模型计算相结合的方法,分析开槽前后该河段的水流及泥沙运输特性。新开航槽后,左汊分流明显,滩口段流态得到明显改善;随着来流量的增加,新槽成为泥沙主要输移路径,且新槽内仅洪水期出现少量泥沙淤积现象;同时卵石推移质运动满足洪淤枯冲和年内冲淤平衡规律,两汊航槽稳定性较好。

The Zhajiao reach is a typical branching reach in the upper Yangtze River,which has low water obstruction to navigation of curving and shallow water channel with a high velocity.Based on the navigational characteristics,the regulation scheme of navigation by two branches is put forward.By a combination method of physical model experiment and two-dimensional numerical model calculation of water and sediment,the characteristics of water flow and sediment transport before and after excavation are analyzed.While excavating the new channel,the left branch diverges obviously,and the flow pattern in the beach mouth is improved.The new channel becomes the main transport path of sediment with the increase of the coming flow,and there is little sediment deposition.Meantime the bed load movement of pebbles meets the law of flood-silting and dry-scouring balance within a year,and the two branching channels stability is good.