Analysis of bridge failures due to scouring has been extensively studied by different researchers in recent years and as a result various methods of controlling local scour cavity have been given. Since most of the research in this field has been done on straight paths and also the complexity of the flow pattern in bends, studying the scouring pattern around the bridge piers located in the bends has become a necessity. Therefore, one of the main objectives of this study is to investigate the scouring around the circular piers which are protected by collars at the river bends. The performance of the collar significantly depends on its level around the pier, which has been studied in this study. The results showed that the optimal performance of this structure, in positions 60°, 90° and 120° at the level of 0.2 pier width under the bed with 3 mm thickness (0.06 of pier width) by approximately 68, 63 and 70% of the maximum pier scour depth was reduced compared with collarless pier, respectively. By analyzing the results of this research, it was observed that the optimum level range of collar around the pier at various bend angles is the initial bed level up to 0.4 times the pier width at the bottom of the incipient level of the bed. Moreover, getting closer to the plate placement level toward the initial bed elevation enhances the collar’s function in decreasing scouring.

近年来，不同的研究人员对桥梁冲刷破坏分析进行了广泛的研究，并提出了各种控制局部冲刷空洞的方法。由于该领域的大部分研究都是在直线路径上进行的，而且弯道处流型的复杂性，研究位于弯道处的桥墩周围的冲刷模式已成为必要。因此，本研究的主要目标之一是调查河湾处受项圈保护的圆形桥墩周围的冲刷情况。项圈的性能很大程度上取决于其在桥墩周围的水平面，本研究对此进行了研究。结果表明，该结构在3 mm厚度（0.06墩宽）床身下0.2墩宽水平处的60°、90°和120°位置上的性能最佳，分别为3mm厚（0.06墩宽）的68%、63%和70%。与无领桥墩相比，最大桥墩冲刷深度有所减小。通过分析本研究的结果，发现在不同弯曲角度下，桥墩周围接箍的最佳水平范围是初始河床水平至河床初始水平底部的桥墩宽度的0.4倍。此外，越接近初始床高程的板放置水平增强了套环减少冲刷的功能。