Analysis On The Influence Of Foundation Scouring On Mechanical Property Of Heavy Haul Railway Bridge And Protective Measures

With the fast development of railway transport in China,a large number of river-crossing and railway bridges were built one after another.River water scours bridge piers and foundation,which will further shallow the embedded depth of foundation,reduce the stiffness of bridge,pier and foundation and influence the stability of the bridge superstructure.In addition,the lateral swing force of the heavy-haul railway transport increases due to the increment of train axle load,which further affects the stability of the bridge superstructure.Under the common effect,it is easy to excess the limit of later amplitude on the pier's top.This paper focuses on the study of the influence of scouring effect on the mechanical property of heavy haul railway bridges and the protective measures.The main research contents and the conclusions are shown as follows:(1)The accuracy of the calculation formulas for the local scour of bridge piers commonly used at home and abroad was compared and analyzed based on the engineering examples.The analysis results show that the local scour calculation formula 65-1 in the “Code for Rating Existing Railway Bridges” considers too many correction factors.Although the formula has a complex calculation,the calculation results are secure and accurate;and Bao's formula has limited accuracy,but it involves low security risks with easy calculation,and is suitable for rapid calculation in the project.(2)The basic stiffness of the bridge was studied using the m method.The calculation results show that: under the same design form,the foundation piles of high-pile pile foundations have larger diameters and greater stiffness;the greater the center distance of the pile foundations,the greater the rigidity;the foundation piles of low-pile pile caps are in the same design form and are circular.The larger the diameter of the shape of the pier,the greater the stiffness;for different piers,the calculation method of stiffness is basically the same.(3)The finite element model of the bridge was established,with the Cihe Grand Bridge as the engineering background,to analyze the influence of the scouring depth,the train axle load and the train speed on the lateral amplitude on the the pier top.The results show that the lateral amplitude on the pier top gradually increases with the increase of the scouring depth and the train axial load;when the scouring depth reaches the maximum local scour line,the lateral amplitude on the pier top increases approximately twice as compared with the part that is not scoured;the lateral amplitude under the effect of the train axle load 27 t is about 30% larger than that of the train axle load 21 t;in the range of 35 km/h to 60 km/h,the lateral amplitude on the pier top increases and then decreases with the speed of the train,and the minimum value of the lateral amplitude on the pier top is about 50% of the maximum value.(4)The applicable anti-scouring measures were studied for the bridge foundations with different degrees of scour,and were verified by the reinforcement measures and protective measures of the heavy haul railway bridge Cihe Grand Bridge after scouring.