并线桥墩局部冲刷试验研究

Experimental study on local erosion of bridge group piers

针对并线桥墩在多沙河流上的局部冲刷问题,采用1:100正态模型水槽对桥梁平面正交在不同形状、上下游不同桥梁间距的桥墩布置进行了系列试验研究,对上下游桥墩在不同水流强度、不同桥梁间距条件下的局部冲刷过程进行系统观测和分析。结果表明,桥墩并线时,桥墩周围水流流态较为复杂,受上游墩阻水绕流影响,下游墩周围水流紊动强度减小,流速减弱。当上下游桥墩距离较近时,上下游桥墩局部冲刷坑深度均小于相应单独桥墩,下游桥墩冲深小于上游桥墩冲深,这种差异随桥梁间距的增大而逐步减弱。随着水流强度及桥墩尺度的增大,下游桥墩不受上游桥墩影响的距离相应增大,当流速为2 m/s、墩径为2~8 m时,其影响距离约为350~660 m。

A series of experiment were carried out on piers with different shapes and different distances orthogonal bridges by a flume with a slope of 1: 100. The local scour processes of upstream and downstream piers under different flow intensities and bridge distances are studied. Results show that the flow regime around piers is rather complicate,and the flow intensity velocity of the flow turbulence around the downstream piers decreases due to the influence by the resistance of upstream piers to water flow when the piers are aligned. When the distance between the upstream pier and downstream pier are close relatively,the local scour pit depth of the upstream and downstream piers are smaller as the corresponding individual pier. Scour depths around the downstream pier are smaller than that of the upstream pier. With the increase of flow intensity and pier diameter,the distance of downstream pier unaffected by upstream pier also increases correspondingly. When the flow velocity is 2 m/s and the pier diameter is 2 ~ 8 m,the influence distance is about 350 ~ 660 m.