FAILURE BEHAVIOR OF RIPRAP LAYER AT BRIDGE PIERS UNDER LIVE-BED CONDITIONS
FAILURE BEHAVIOR OF RIPRAP LAYER AT BRIDGE PIERS UNDER LIVE-BED CONDITIONS
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DOI：
10.1061/(asce)0733-9429(2000)126:1(43
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发表时间：
2000
影响因子：
2.4
通讯作者：
Y. Chiew;F. Lim
中科院分区：
文献类型：
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作者：
Y. Chiew;F. Lim
在活床条件下进行的实验表明，圆柱形桥墩处的抛石层将以以下两种模式之一失效：完全崩解或嵌入。前者是指整个抛石层的破碎，石块被桥墩处产生的流场冲走。后者与抛石层埋藏在沉积物床中的情况有关。该研究提出了一个标准来划分两种类型失效之间的限制条件。它还表明，嵌入破坏是活床条件下抛石层更常见的破坏模式。埋置失败的原因有两个：（1）地床特征不稳定； (2) 不同的迁移率。床面特征传播引起的床面波动导致床面失稳，而差异流动性则是由于抛石块和床面沉积物对流场的不同响应造成的。实验结果还表明，对于给定的流动条件，抛石层可以退化到平衡水平。最后，该研究提出了一个半经验方程来计算发生在沙丘上端的抛石退化的最大深度。
Experiments conducted under live-bed conditions show that a riprap layer at a cylindrical bridge pier will fail in either one of the following two modes: Total disintegration or embedment. The former refers to the break-up of the entire riprap layer where the stones are washed away by the flow field generated at the pier. The latter relates to the embedment of the riprap layer where it is buried in the sediment bed. The study proposes a criterion to demarcate the limiting condition between the two types of failure. It also identifies that embedment failure is a more common failure mode of riprap layer under live-bed conditions. The causes of embedment failure are twofold: (1) bed feature destabilization; and (2) differential mobility. Bed level fluctuations caused by the propagating bed features resulted in bed feature destabilization, whereas differential mobility is due to the different response of the riprap stones and bed sediments to the flow field. Experimental results also show that the riprap layer can degrade to an equilibrium level for a given flow condition. Finally, the study proposes a semiempirical equation to compute the maximum depth of riprap degradation, which occurs at the upper end of dune regime.