长江口北支崇启大桥处潮位和盐度过程研究

位于长江口北支的崇启大桥处于盐淡水交替区,其混凝土桥墩易受海水腐蚀。为给桥墩抗腐试验提供必要的潮位变动区范围和盐度试验参数,建立了基于无结构网格的长江口盐水数值模型,计算分析了在不同径流量和外海潮汐边界条件下,崇启大桥断面潮位变幅及盐度变动过程。研究表明崇启大桥处潮位变幅大,潮汐是控制崇启大桥处水位变动范围的关键因素;桥墩处盐度整体取决于入海径流量,流量增加促使盐度降低,反之亦然;潮汐作用促使桥墩处呈现短周期性振荡盐度,盐度范围为10‰～26‰,其中枯季盐度平稳,洪季变幅大。

A modeling study on tidal and salinity process at Chongqi Bridge cross section located in North Branch of Yangtze Estuary

For the Chongqi Bridge located in the mixing zone of fresh-salt water in the North Branch of Yangtze Estuary,the concrete of piers can be eroded easily in the salt water.In order to provide the tidal fluctuation zone in vertical direction and the salinity values required in the anti-erosion tests of concrete,a hydrodynamic and saltwater intrusion model of Yangtze Estuary was developed and calibrated by the TELEMAC model.The tidal level and the salinity at the cross section of the bridge were simulated under conditions of the different characteristic discharges corresponding to the different cumulative frequencies.The results show that tide is the key factor resulting in the water level fluctuation,and the salinity at the cross section is decided by the runoff from Yangtze River watershed.The more flow rate is,the lower salinity is.The salinity also ranges within 10‰～26‰ in the same period with the tide under the action of tide.The fluctuation extent in spring season is larger than that in dry season although the salinity is smaller.