桥墩对弯槽段冰塞形成的临界条件及冰厚变化影响的试验研究

发布时间：2018-07-16 22:28

【摘要】：冬季,我国北方寒冷地区的河流经常产生冰塞或冰坝现象,冰塞的出现会减小过水断面面积,减小冰盖下的过流能力,使河道中的水位显著壅高。水位的壅高,或者冰塞体解体溃决时导致的冰凌洪水,常常使河道的上、下游发生淹没灾害,给国计民生带来重大的损失。同时,河道中桥墩的存在进一步改变了原有的水力条件和边界条件,对冰塞形成及演变产生影响,加剧了河道中桥梁的安全威胁。因而开展桥墩对冰塞形成的临界条件及厚度变化的影响分析对预防冰凌灾害具有重要的意义。借助于实验室的试验水槽,通过改变水流条件和冰流量条件,研究了桥墩存在以及桥墩位置不同时对冰塞形成的临界条件和演变过程的影响。试验结果表明:桥墩的存在改变了桥墩附近的水流结构,使得桥墩附近水流输冰能力相对增大,同水流条件下,冰塞的形成将需要更大的冰流量条件;同水流条件下,与单墩放置于两弯连接处的直道段相比,单墩放置于弯道顶点处时,桥墩断面处冰塞形成需要更大的冰水流量比。相比于将桥墩安置在两弯连接直道段,将桥墩安置于弯道顶点处时,桥墩附近水流输冰能力增大;在两弯连接的直道段和弯道顶点处同时放置桥墩时,弯道平衡冰塞厚度介于单墩放置于两弯连接的直道段与单墩放置于弯道顶点处时的弯道平衡冰塞厚度之间。因此,当桥墩放置于弯道顶点处时,可将冰塞的不利影响减小到最低。
[Abstract]:In winter, ice jams or ice dams often occur in rivers in the cold regions of northern China. The appearance of ice jams will reduce the cross section area and reduce the overflow capacity under the ice cap, which will make the water level in the river stand significantly higher. The flood caused by the high water level or ice flood caused by the breakup and collapse of the ice slug often causes the flood disaster in the upper and lower reaches of the river and brings great losses to the national economy and the people's livelihood. At the same time, the existence of bridge piers in the river channel has further changed the original hydraulic conditions and boundary conditions, which has an impact on the formation and evolution of ice jams, and intensifies the threats to the safety of bridges in the river channels. Therefore, it is of great significance to analyze the influence of pier on the critical condition and thickness change of ice slug formation. By changing the conditions of flow and ice flow, the influence of the existence of piers and the location of piers on the critical conditions and evolution process of ice slug formation is studied by means of the experimental flume in the laboratory. The experimental results show that the existence of piers changes the flow structure near the piers, which makes the ice transport capacity of the bridge piers relatively larger. Under the same water flow conditions, the formation of ice slugs will require greater ice flow conditions, while under the same water flow conditions, the formation of ice slugs will require greater ice flow conditions. Compared with the straight section where the single pier is placed at the junction of two bends, when the single pier is placed at the top of the bend, the formation of ice slug at the section of the pier requires a larger ratio of ice to water flow. When the piers are placed in the straight section of the connection between two bends and the piers are placed at the top of the bend, the ice transport capacity near the piers increases, and the piers are placed at the straight section and the top of the bend at the same time. The thickness of the equilibrium ice plug is between the thickness of the single pier placed in the straight section of the connection between the two bends and the thickness of the equilibrium ice plug of the bend when the single pier is placed at the top of the bend. Therefore, when the pier is placed at the top of the bend, the adverse effects of the ice plug can be minimized.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U443.22;U442.3

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