Research On Deformation Control Technology Of High Railway Foundation In Construction Transition Section

With the rapid development of high-speed railways,the running speed of trains has been continuously improved.In order to meet the safety and comfort of driving,the differential settlement requirements of the transition section of high-speed railway foundation construction are also getting higher and higher.In this paper,numerical simulation and theoretical analysis are used as research methods to systematically analyze the differential settlement law of construction transition section.And put forward a treatment plan for the transition section of the high-speed railway construction on the soft foundation.This paper first discussed the deformation treatment measures of the construction transition section of the roadbed and foundation,contrasted and analyzed the advantages and disadvantages of various foundation treatment methods and adaptation conditions,and discussed the reinforcement mechanism of the CFG pile composite foundation,and concluded that the settlement control of the CFG pile composite foundation It is the most suitable treatment plan.Based on FLAC 3D,a three-dimensional finite element numerical model of the transition section of high-speed railway foundation construction was established,and the transverse and longitudinal settlement changes of the transition section of the construction transition section were calculated.At the same time,the influence of the structural form and subgrade parameters on the settlement and deformation of the top surface of the transition section of the construction transition section was studied.It was found that the influence of the slope gradient on the toe displacement of the inverted trapezoid transition section was much greater than that of the normal trapezoid.And some suggestions were given for the value of the cushion layer thickness.Based on the normal trapezoid construction transition section,several CFG pile composite foundation treatment schemes were proposed,and a three-dimensional numerical model of the subgrade-CFG pile composite foundation was established.The influence of pile layout,pile spacing,pile length and pile modulus on the top of the construction transition section was studied.According to the influence of surface settlement and deformation,the law of longitudinal settlement of the construction transition section was obtained.Through the comparison and analysis of several treatment schemes,it was obtained that by changing the pile length,pile spacing and pile modulus of each part of the transition section(from the transition section to the general road section)Where the pile spacing increases,the pile length and the pile body modulus decrease in order),the bearing capacity of the composite foundation can be effectively improved,and the purpose of smooth transition of the line can be achieved.According to the treatment plan proposed in the article,the dynamic analysis of the CFG pile composite foundation in the transition section of the construction under the cyclic load of the train was carried out,and the dynamic stress distribution law of the CFG pile composite foundation in the transition section under the train load was obtained along the depth direction,that is,the dynamic stress increases with The increase in depth continues to attenuate,and its effective impact depth is 9 m.The settlement of the top surface of the roadbed during the operation period was predicted.The results show that after the train has been running for 20 years,the cumulative settlement of the top surface of the roadbed will be 25.85 mm.