Calculation On The Local Scour Surrounding Steel Pipe Piles Of Sea-Crossing Bridges

Steel pipe piles are widely used in the fields of foundation engineering,bracket engineering and large-scale sea-crossing bridges because of their simple fabrication,high applicability,convenient construction and high strength.Bridge damage is one of the most important disasters faced by sea-crossing bridges,and its main cause is caused by local scouring.Accurate prediction of maximum scour depth around piles is the basis of safe operation of cross-sea bridges.Due to the complex flow field around piers,the scour depth of the pier is still unable to be accurately predicted.In recent years,the use of computational fluid dynamics software has become the main means of bridge foundation scouring research.In this paper,the local scour of steel pipe piles is deeply studied on the basis of cylindrical piers by means of test model and simulation.The main research contents and conclusions are as follows:(1)Based on the theoretical analysis of fluid mechanics and the interaction of water-pier-sand,the scour of steel pipe pile is analyzed theoretically,revealing the interaction mechanism of water-pier-sediment.Various calculation formulas of local scour of typical pier and their application scope are elaborated.The limitations of local scour prediction formulas for piers are pointed out by comparing with engineering design codes.(2)Based on Melville’s classical flume test,a three-dimensional simulation model with the same scale was established by FLOW-3D numerical simulation software.The experimental model is simulated and the results are analyzed.The flow field distribution,scouring range and scour depth are obtained.The accuracy of the simulation model for simulating flow field and scour around piers are verified.(3)The influence of scouring depth of double-cylinder pier and single-cylinder pier is studied.The results show that the scour depth of downstream piers decreases with the decrease of the angle between piers,and the maximum scour depth occurs on the unimpeded side.In addition,the protection of sacrificial piles is studied.The scour depth of downstream piers under the protection of sacrificial piles decreases obviously.With the increase of the diameter of sacrificial piles and the increase of the distance between sacrificial piles,the scour depth decreases first,then increases gradually until the formation of independent scour.