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中文核心期刊

桥墩-冰塞-局部冲刷相关问题研究进展

ADVANCES IN RESEARCH WORK REGARDING IMPACTS OF BRIDGE PIERS ON ICE ACCUMULATION AND LOCAL SCOUR PROCESSES

  • 摘要: 桥梁建设改变了河流的边界条件、水流条件和河床泥沙的运动状态,冬季河流中有冰塞出现时则产生相互影响作用.近年来,基于冰塞稳定性力学分析,开展了桥墩影响下冰塞稳定性研究,所得桥墩影响下冰塞稳定性判别公式计算结果和实测资料能够较好得吻合;研究了桥墩对河道卡封以及临界流凌密度的影响,计算得到的临界流凌密度与实验值较为接近;介绍了明流、冰盖下桥墩周围局部冲刷等方面的相关研究工作,得出了冰盖条件下桥墩局部最大冲刷深度的回归经验公式,结果表明该公式具有很好的适用范围.对冰塞条件下桥墩附近局部冲刷问题探索性地开展了试验研究,研究表明,冰塞条件下的局部冲刷与冰盖条件下有着很大不同,不仅冲刷深度要大的多,而且桥墩周围局部冲刷过程与冰塞厚度变化相关.在冰塞条件下,桥墩处的最大冲刷深度和最大冲刷长度均随流速增大而增大,冲刷坑尾部淤积沙丘高度也受到流速的影响.就相关研究难点和今后需要进一步开展的研究工作进行了分析和展望.

     

    Abstract: River ice is an important factor affecting alluvial channels in winter. The appearance of bridge piers in channel changes the flow condition, and therefore affects the accumulation or ice jam process around bridge pier. On the other side, under ice-covered conditions, due to the extra boundary imposed by ice cover, the location of the maximum flow velocity is closer to the riverbed. Consequently, the riverbed scour around bridge pier under ice cover should be greater than in the absence of ice cover. By means of mechanical analysis of the stability of ice jams around bridge piers, a formula has been proposed to assess the stability of ice jams under the influence of bridge piers. The calculated results using the proposed formula were in good agreement with those measured in laboratory. Experiments have been conducted to study the impacts of bridge piers on the initiation of an ice cover. A formula for determining the critical concentration of ice floes on water surface for initiating an ice cover around bridge piers was developed. The proposed equation has been validated by data collected in laboratory and natural rivers. The relevant research works with respect to the local scour process around bridge piers/bridge abutments under both open flow and ice-covered (ice-jammed) flow conditions have been carried out in laboratory. Considering different bed material, pier size and ice-cover roughness, empirical formulas have been developed to calculate the maximum scour depth in the vicinity of bridge piers under ice-covered condition. Laboratory experiments have been conducted to study the local scour process around bridge piers under the ice-jammed flow condition. Results show that, under an ice-jammed flow condition, the local scour depth around bridge piers is much more than that under a sheet-ice-covered flow condition. Also, the bed deformation interacts with ice accumulation; namely, the thicker the ice jam, the more the scour depth, and vice versa. Under an ice-jammed condition, both the maximum depth and length of scour holes around a bridge pier increase with the flow velocity. Also, the height of a deposition dune downstream of a scour hole is affected by flow velocity This paper also summarizes further research work that needs to be carried out in the future.

     

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