Formation, Growth, and Failure of Debris Jams at Bridge Piers
Formation, Growth, and Failure of Debris Jams at Bridge Piers
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DOI：
10.1029/2017wr022177
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发表时间：
2018-09
影响因子：
5.4
通讯作者：
D. Panici;Gustavo A. M. de Almeida
中科院分区：
文献类型：
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作者：
D. Panici;Gustavo A. M. de Almeida
桥墩周围堆积的大量木屑阻碍水流，导致上游水位升高、水平结构荷载增大以及流场改变，从而大大加剧冲刷。这些影响经常被认为是造成世界各地大量桥梁倒塌以及邻近地区洪水泛滥风险增加的原因。然而，目前对这些碎片堆的形成和增长的时间演变和过程知之甚少。本文的目的是通过一套详尽的570个实验，其中碎片元素被单独引入水槽和积累在下游的桥墩模型，破译整个寿命的碎片积累。我们的研究结果表明，在所有的实验中，积累的增长是停止在一个关键阶段，之后的堵塞是从码头的流动。这个条件通常与累积的维数达到最大值的时间一致。累积最大尺寸的值显示出明显的依赖于流动特性和碎片长度分布。另一方面，其他变量对堆积的几何形状的影响要弱得多。对于一个给定的碎片长度，积累是宽，浅，长在低流速，但变得更窄，更深，更短的速度增加。对大小分布均匀和不均匀的碎片所形成的堆积物的结果进行比较后发现，前者的宽度可达后者的2.5倍。
The accumulation of large wood debris around bridge piers obstructs the flow, producing increased upstream water levels, large horizontal structural loadings, and flow field modifications that can considerably exacerbate scour. These effects have frequently been held responsible for the failure of a large number of bridges around the world, as well as for increased risk of flooding of adjacent areas. Yet little is currently known about the time evolution and processes responsible for the formation and growth of these debris piles. This paper is aimed at deciphering the whole life of debris accumulations through an exhaustive set of 570 experiments in which debris elements were individually introduced into a flume and accumulated at a pier model downstream. Our findings show that in all experiments, the growth of accumulations is halted at a critical stage, after which the jam is removed from the pier by the flow. This condition typically coincides with the time when the dimensions of the accumulations are maxima. The values of the accumulation maximum size display a clear dependence on flow characteristics and debris length distribution. On the other hand, other variables have shown much weaker effects on the geometry of the accumulations. For a given debris length, accumulations are wide, shallow, and long at low flow velocities but become narrower, deeper, and shorter with increasing velocities. A comparison of results of accumulations formed with debris of uniform and nonuniform size distributions has revealed that the former can be up to 2.5 times wider than the latter.