潮汐河段桥墩局部冲刷深度的试验研究

随着公路延伸到潮汐河道和近海海港,在桥梁设计中需要对潮汐河段桥墩的局部冲刷深度进行分析。在动床模型试验中使用了典型的潮汐水流条件和3种代表性的模型沙。使用拍照和测量记录下冲刷坑的形态和深度变化过程,得到了潮汐河段桥墩的冲刷过程,将潮流冲刷的深度与恒定流的深度进行比较,得出不同条件下冲刷深度的折减系数为0.75~0.92,建议以涨落急最大流速代替恒定流流速作为计算的标准,试验结果还表明泥沙粒径小于0.15 mm条件下的公式计算结果与试验结果有差别,建议对公式进行修正。

Experimental research on pier local scour depth over tidal waterways

As highway extends to tidal waterways and offshore harbors,analysis of the pier local scour depth over tidal waterways becomes necessary in design of a bridge.In this paper,typical condition of tidal flow and three kinds of representative model sand were used in the mobile bed model test.By photographing and measuring,the depth and shape of scour hole were recorded,thus obtaining the scour progress.Then by comparing the scour depth in tidal current and that in constant flow,the reduction factors of scour under different conditions were obtained,which were from 0.75 to 0.92.The maximum velocity of rising tide and tide ebb was suggested to replace constant flow velocity,which used to be a major factor in formula.Results of the experiment indicate that when the particle size of sand is smaller than 0.15 millimeter,deviation occurs between the result of formula calculation and that of the test,which recommend an improvement for the formula in standard.