连续弯曲河道段桥位布置及通航安全分析

Bridge layout over the continuous meandering river sects and analysis of the navigation safety concerned

基于MMG船舶操纵运动数学模型基本理论,利用龙格-库塔方法进行积分计算求解方程组,将船舶的各受力方程结合流场数学模型计算的表面流场数据在MATlAB软件中编制成船舶操纵运动数值模拟可视化程序,以洞庭湖澧水洪道安乡大桥建设工程为背景,计算分析桥梁建设后航道弯曲半径及桥前直线段距离对通航安全的影响。结果表明,船队通过连续弯曲河道出弯时占用的航宽增大,千吨级航道中的弯曲半径取《内河通航标准》中单弯情况规定的最小值480 m时,上游出弯口与大桥间的安全直线段距离需6倍船长以上。距离为5倍船长时,航道弯曲半径应增大至550 m,无法达到相应的航道弯曲半径时,下游桥孔的通航跨距应相应增加15.8%。

This paper is inclined to analyze the impacts of the bridge layout over the continuous meandering river sects and the navigation safety concerned.To solve the above mentioned research task,we have taken the construction project of Anxiang Bridge over Lishui Flood Passage on the Dongting Lake,Hunan,as a study sample.To solve the complicated calculation program,we have resorted to the Runge-Kutta method to solve the integral equations based on the fundamental theory of MMG mathematical model of ship maneuvering motion in the construction typical of the continuous downstream bends.To accomplish the tremendous calculation volume,we have worked out each force equation of the ship and the data on the surface flow field by the fluid field mathematical model.In addition,we have also adopted a visual program for numerical simulation of ship maneuvering motions via a MATLAB software.As can be seen from the calculated results,when the ship passes through a bend exit of the continuous meandering river section,there may exist a series of factors affecting the navigation safety,such as the ship position and the deviation distance change under the impact of the curvature radius of the downstream bends.Thus,a problem may come about as the curvature radius decreases：the width of waterway needed for the ship to pass through the bend and the straight-line distance for the ship to adjust its own position with other ships when they get closer.Thus,to ensure the navigation safety,problems are to be solved as to the straight-line distance in front of the bridge and the navigable span of the downstream bridge opening in relation to the curvature radius of the upstream bend or bends.Therefore,if the minimum curvature radius of a single-bend river section is taken for a 1 000 t waterway as specified in the Navigation Standard of Inland Waterway,i.e.480 m,the safe straight-line distance from the upstream bend exit to the bridge itself should be over 6 times as much as the length of the ship for a standard navigable span.Moreover,if the distance is 5 times as much as the ship length,the curvature radius of the waterway should be made to reach 550 m.What is more,if the corresponding curvature radius of the waterway fails to reach the specified standard,it would be necessary for the navigable span of the downstream bridge opening to increase by 15.8%,accordingly.