Analysis On The Influence Of Foundation Reinforcement On The Operation Performance Of Heavy-haul Railway Bridge

With the rapid development of China's freight railway,the increasing axle load and annual traffic volume of the train put forward higher traffic requirements for the bridge and culvert engineering structure of the existing railway.Due to the weak foundation caused by the low early design standard,poor construction quality,operation damage and natural disasters(such as scouring)and other reasons,the railway transportation safety has been affected to a certain extent.Some existing railway bridges can no longer meet the development trend of heavy load transportation and the demand of safe operation.It is urgent to strengthen it and improve its performance.At present,in view of the existing heavy-duty railway bridge foundation reinforcement,especially the foundation reinforcement carried out on the premise of not interrupting the railway freight transportation,it will inevitably have a certain degree of impact on the normal operation of the railway bridge.This paper is based on the project of pile foundation reinforcement by impact drilling method of Cihe Grand Bridge of Shuohuang heavy-haul railway.The main research contents and conclusions are as follows:(1)Considering the factors such as low clearance under the bridge,soil condition of river bed,convenience of site construction and little disturbance to the structure and operation train,the paper puts forward the pile foundation expansion and reinforcement technology based on the impact drilling method,formulates the construction process and key construction process of the reinforcement method,and studies the different axle load and no load during the foundation reinforcement construction through theoretical analysis the influence rule of the same speed train and normal traffic on the operation performance parameters of the bridge,and according to the analysis results,the speed limit Countermeasures of the train crossing the bridge are put forward.(2)Based on MIDAS/GTS software,the finite element model of the whole process of foundation reinforcement construction of Cihe Grand Bridge is established.The influence of construction factors such as excavation method,excavation depth,impact drilling position and hole forming sequence around the bearing platform on the evaluation parameters of railway bridge operation performance,such as transverse amplitude of main beam in midspan and pier top,is analyzed.Taking the allowable value of normal operation performance as the optimization objective,the optimal foundation is obtained the relationship between the reinforcement scheme and the maximum running speed of different axle load trains passing through the bridge.(3)The monitoring scheme for the foundation reinforcement construction of Cihe Grand Bridge of heavy-haul railway in service is formulated,and the static and dynamic observation parameters,key positions and numbers of measurement points and observation frequency in the reinforcement construction of the bridge are proposed and optimized.The real-time evaluation and early warning system for the operation performance of the bridge is established by combining the numerical analysis.By comparing the measured data with the theoretical analysis results,the applicability and correctness of the numerical analysis of the finite element model in the optimization of the railway bridge foundation reinforcement construction are verified.The optimized construction scheme and the proposed speed limit scheme also ensure that the transverse amplitude of the main beam in the middle of the span and the transverse amplitude of the pier top are controlled within the reasonable allowable range,thus realizing the foundation reinforcement without interrupting the heavy-haul railway transportation Mark.