Abstract: In order to explore the comprehensive influence of spur dike construction and naturally unsteady incoming flow on the main streamline of the channel, the unsteady flow two-dimensional shallow water model was used to calculate the flow field distribution of the regulation reach of a single spur dike in the upper reaches of the Yangtze River during a typical flood process. And the characteristics of the mainstream line of the reach and its impact on navigation safety were analyzed. The spatial and temporal variation characteristics of the mainstream were defined and calculated. The research shows that the mainstream line of the spur dike regulation reach has significant characteristics of zoning along the way, and it is recommended to divide the reach along the flow direction into 6 characteristic intervals with the dam axis as the boundary. The mainstream line in the near area behind the dam is the most tortuous and unstable (the tortuous degree is severe, the wandering swing degree is drastic, and the maximum swing amplitude reaches 30% of the river width). A stable deflection of nearly 40° from the opposite bank to the bank where the dam is located occurs in the reach near the dam axis, which affects navigation safety. At a distance of 8.4 times the dam length at the upstream and 23.6 times the dam length at the downstream from the dam axis, the mainstream line is straight and stable, which does not affect the navigation safety during the flood.

Key words: waterway engineering; spur dike regulation reach; flood process; mainstream line; navigation safety; numerical calculation

摘要： 为探明丁坝的修建和天然非恒定来流对航道主流线的综合影响，采用非恒定流二维浅水模型，计算了典型洪水过程中长江上游单丁坝整治河段的流场分布，分析了河段主流线特征及其对通航安全的影响；定义并计算了主流线的空间和时间变化特征。研究表明：丁坝整治河段主流线具有显著的沿程分区特点，推荐以坝轴线为界将河段沿水流方向划分6个特征区间；在坝后近区主流线最曲折、最不稳定（曲折程度为重度，游荡摆动程度为剧烈，最大摆动幅度为河宽的30%），在坝轴线附近河段发生从对岸向坝所在岸近40°的稳定偏转，影响了通航安全；在上游距离坝轴线8.4倍坝长以外和下游距离坝轴线23.6倍坝长以外，主流线顺直稳定，不影响洪水期间的通航安全。

关键词: 航道工程；丁坝河段；洪水过程；主流线；通航安全；数值计算