A Study On Foundation Reinforcement Technology Of The Bridge-subgrade Transition Section Of High-speed Railway

In recent years,with the rapid development of high speed railways,problems of the differential settlement of bridge-subgrade transition sections have become more and more obvious,especially as for the high speed railways built up under the special foundation conditions such as soft soil.In addition,with the continue increase of train speed and axle loads,more strict requirements are placed on the differential settlement of transition sections.The problem of "bump at bridge-head" has become one of the significant factors that affecting the safety of high speed train.In view of the present situation,this paper based on the theoretical analysis method and numerical calculation method,analyzed the settlement regularity of the bridge-subgrade transition section of high speed railway under the soft soil systematically,and put forward the corresponding method of foundation treatment.First,the paper discussed the common soft ground treatment methods and analyzed the advantages,disadvantages and applicability of each method.It is concluded that the CFG pile composite foundation is more suitable for the foundation treatment of bridge-subgrade transition section of the high speed railway in soft soil area.Then,based on the finite element method,the paper established the two-dimensional numerical model of transition section,and calculated the settlement regularity along the longitudinal of bridge-subgrade transition section roadbed.In addition,it analyzed the influence of the variation of transition section material parameters to subgrade settlement.On the basis,the paper put forward several CFG pile composite foundation treatments of transition section,and analyzed the transition effect for differential settlement of each method.The results could optimize the CFG pile composite foundation treatment methods of bridge-subgrade transition section of high speed railway under the soft foundation.Finally,the paper established a three-dimensional finite element dynamic model of the track-subgrade-CFG pile composite foundation of bridge-subgrade transition section of high speed railway which is based on a CFG pile composite foundation treatment method proposed in this paper Based on this model.the paper analyzed the dynamic stress distribution regularity of the composite foundation and the attenuation characteristics of vertical acceleration of the pile and the soil along the subgrade lateral and depth by the affection of the train excitation load.The conclusions of this paper can enrich the foundation reinforcement technology of bridge-subgrade transition section of high speed railway.It can be used as reference for the foundation treatment of transition section in soft soil and the similar projects.