Reserch On The Depth Of Local Scour At Bridge Piers Under The Actions Of Tidal Current At Estuaries

Bridges play a extremely important role in China’s transportation, the safeoperation of bridge is the basic guarantee for China’s economic development.According to statistics, flood damage is one of the important causes of bridge failure.However, local scour is one of the main factors causing the flood damage of bridge, soto accurately predict the depth of local scour and reasonable decorate embedded depthof piers are the guarantees of the bridge safe operation. The experts and scholars havebuilt on the river bridge pier local scour depth and a lot of in-depth scientific researchpreviously and greated multiple bridge pier local scour depth formula for the design ofbridge. However, with the constant innovation and development of bridge constructiontechnology in China and the rapid economic development of coastal areas, large andsuper large bridges are springing up in China’s coastal areas. Most of these piers in thetide of flow condition which is very complex and bridge structures are diversified andvarious, the old formula has been difficult to apply to the current situation. In order toensure building bridges safety in the area, there is urgent need to conduct acomprehensive and in-depth exploration on the local scour under the actions of tidalcurrent.Nowadays, the calculation of local scour depth are based on the characteristics ofthe bridge condition, the flow field near the piers and sediment conditions both bridgedesign and scientific research according to the standard formula to calculate thecorresponding results. However, because the water environment near the bridge pier isvery complicated, local scour mechanism and related theory still has not been adequate.Paper is intended to on the basis of induce the previous research results domestic andforeign, factors affecting the bridge pier local scour depth are summarized. Paper isgoing to elicit the bridge pier local scour formula by dimensional analysis and multiplelinear regression analysis and combining with a large number of measured data.According to the tide power characteristics of the Oujiang estuary region where77provincial highway extensions is located in, the sea area is numerical simulated bythe finite element mathematical model software. This paper has made detailedexplanations to the simulate the flow condition around the Doutouxia bridge，Shenmenbridge and Qianmen birdge. The methods of large and small models are nested toimprove the simulation accuracy of the mathematical model for the hydrodynamic characteristics of engineering area. The new formula of bridge pier local scour after thevalidation and some commonly used local scour formulas are adopted to theengineering calculation, and then the results are compared and analysis.According to the comparison and analysis on the calculation results between thenew formula and some commonly used local scour formulas, the new formula ofbridge pier local scour which build in this paper is simple and high calculationaccuracy. So it can be used to provide a reference basis in estimating the local scourdepth arund related areas.