Research On The Influence Of The Pile Foundation Settlement Of The Newly-built Cross-line Bridge On The Deformation Of The Existing High Railway Foundation

In recent years,with the rapid development of China's high-speed railway and highway construction,the density of the two road networks has continued to increase,which has also led to a gradual increase in the intersection between railway and highway.When a new expressway crosses an existing high-speed railway,it is necessary to adopt corresponding engineering schemes to complete the expressway crossing the high-speed railway line under the normal operation of the existing high-speed railway line,and use bridges to cross the high-speed railway line.Therefore,it is very important to study the influence of the construction of the cross-line bridge on the additional settlement of the high-speed railway foundation.In this paper,based on the theory of pile foundation settlement,taking the Haikou Ring Road Meilan Airport to Yanfeng section of the road as the engineering background,the bridge across the Hainan East Loop Railway is used as the engineering background.The influence of the construction stage of the bridge pile foundation,the construction stage of the superstructure and the operation stage of the bridge on the additional settlement of the U-groove embankment of the Hainan East Ring Road when the newly built expressway bridge crosses the existing high-speed railway line is studied.The Mindelin-Gades method was used for theoretical calculation of group pile settlement.The results of numerical simulation and theoretical calculation were compared and analyzed,and the effect of pile foundation settlement on the additional settlement of U-groove of high-speed railway was obtained.According to the results of numerical simulation and theoretical calculation,the treatment measures for isolation piles are proposed.Finally,the treatment effects of isolation piles are simulated and analyzed.The following conclusions are obtained through numerical simulation analysis and theoretical calculation:(1)In the absence of treatment measures,the overpass bridge will cause a maximum additional settlement of 10.9mm for the U-groove subgrade of the high-speed rail during the operation phase.(2)Due to the large number of Y1 and Z4 main pier piles and the long pile length of the bridge,the construction of the Y1 and Z4 main pier piles has a greater impact on the additional settlement of the U-groove subgrade;while the number of Y2 and Z3 small pier piles is small The length is short,so the construction of Y2 and Z3 small pier pile foundations has little effect on the additional settlement of U-groove subgrade.(3)The numerical simulation results show that in the lateral direction,due to the influence of the pile foundation settlement of the bridge main pier on both sides of theU-shaped groove,the additional surface settlement at the center of the bridge main pier on the left side of the U-shaped groove is the largest.Increase,the surface additional settlement value gradually decreases,decreases to the minimum at the U-groove subgrade,and then as the distance from the center of the main pier of the U-groove bridge decreases,the additional surface subsidence gradually increases,The maximum value is reached at the center of the main pier of the bridge on the right side of the U-shaped groove.(4)Under the combined action of the double main pier loads,the additional surface settlement law of each section calculated by the Mindlin-Gades method is the same as that obtained by numerical simulation.However,because the local reliable empirical coefficient of pile foundation settlement is not available,and the effect of the soil between the pile cap and the pile under the pile cap is ignored,the additional ground settlement calculated by the Mindlin-Gades method is greater than the result of numerical simulation,especially The additional settlement within the range of the bridge cap is much greater than the numerical simulation results.(5)Under the load of a single main pier,the effect of pile foundation settlement on the additional settlement of the ground surface shows that as the distance from the center of the main pier of the bridge increases,the additional settlement of the surface gradually decreases.(6)The numerical simulation results show that the construction of the cross-line bridge has a greater impact on the additional settlement of the U-groove embankment of the Hainan East Ring Road.Therefore,it is proposed to set up isolation piles at appropriate locations between the bridge pile foundation and the U-groove embankment of the Hainan East Ring Line to treat the isolation pile Use bored piles.The treatment effect of the isolation pile is simulated.The treatment effect of the isolation pile is simulated.The numerical simulation results show that: under the shielding effect of the isolation pile,the additional settlement of the U-shaped subgrade is reduced by 2.3 mm,and the isolation pile has a certain treatment effect.