钩环式护圈对冰盖下桥墩局部冲刷影响的试验研究

基于桥墩局部冲刷原理，在水平护圈防冲措施的基础上，设计了一种能改变桥墩周围水流流态的新型防冲设施—钩环式护圈。为探究钩环式护圈对圆柱形桥墩局部冲刷的防护效果，采用不同形状的钩环式护圈进行室内物理模型试验，分析了桥墩周围的冲刷特征和水力特性。试验结果表明：当钩环式护圈的高度为1 cm、角度为135°且安装在床面时，防护效果最好；与光墩相比，桥墩安装钩环式护圈后，最大冲刷深度最多可减小62.2%,桥墩底部垂向流速、垂向紊动强度均明显减小。通过多元回归分析建立了计算桥墩周围无量纲最大冲刷深度的经验方程，该方程对明流和冰盖条件下水流均适用。

Experimental study of influence of ridged collar on local scour of bridge piers under ice sheet

Based on the principle of local scour of bridge piers, and on the basis of the anti-scour measures of horizontal collars, a new anti-scour protection measure, called ridged collar, which can change the water flow around the piers was designed. In order to explore the protective effect of the ridged collar on the local scour of cylindrical bridge piers, indoor physical model tests were conducted using ridged collars of different shapes, and the scour characteristics and hydraulic properties around the pier were studied. The test results show that, the protection effect is the best for a ridged collar installed on the bed surface with a height of 1 cm and an angle of 135°. Compared with cases of no protective measures, after the ridged collar is installed on the bridge pier, the maximum scour depth reduction can reach 62.2%, and the vertical flow velocity and vertical turbulence intensity at the bottom of the pier can be significantly reduced. Through multivariate analysis, an empirical equation for calculating the non-dimensional maximum scour depth around the pier is established, which is applicable to both open channel flows and flows under ice sheet.