Study On Coupling Deformation Between Neighboring Or Connecting Bridge Pile Foundation And High Speed Railway Embankment

Nowadays,high-speed railway has become an important business card of our country across the world.High speed rail way,characterized b y its fastness,safeness,smooth ness and comfort,is changing the way people travel.It is inseparable from stri ct deformation control standards of under-line engineering to realize these characteristics.In this context,the coupling deformation between the bridge pile foundation and su bgrade,as the most common form of foundation under the railway line,has become increasingl y prominent,and become the weak link in engineering design.To sum up,the situation of interaction between bridge pile foundation and subgrade in engineering involves 2 categories: the first category is the adjacent condition,whose characteristic is that the bridge pile foundation and subgrade occur respectivel y in different lines(such as cross bridge engineering);for connecting conditions,it features as bridge pile fou ndation and subgrade bridge pile occur in the same line,i.e.,the bridge-approach project.Although the two forms presented in different forms in engineering and the corresponding design methods are also different,it essentially belongs to the category o f coupling deformation between bridge pile foundation and subgrade.This paper aims to deepen the understanding and cognition on the interaction between pile foundation and subgrade,in order to reveal the inner link of deformation coupling and th us to provide more scientific design methods and ideas for similar engineering practices.Through the stud y of the coupling deformation characteristics between bridge pile foundation and subgrade under the adjacent and connecting conditions,(i.e.AC and C C,respectivel y)the main conclusions and understanding are obtained:Ⅰ.The AC:(1)Based on Mindlin stress solution,using the method of polar coordinates integral Mindlin improvement solution,considering the influences of pile diameter,is derived and used to calculate the bridge pile foundation pile soil mass and adjacent structures of additional settlement,compared with traditional Mindlin-Geddes method at the same time.T he results show that the soil around bridge pile foundation in the settling tank,subsidence of the largest,with the increase of distance from the edge of pile caps,the additional settlement rapidly decreases,and finall y close to zero;Compared with the traditional Mindlin method,the result of Mindlin solution considering pile diameter effect is closer to the experimental value and solves the stress concentration effect of the former.The calculation method considering the geometric parameters of pile section is larger than the centrifugal test value,because the influence of pil e group blocking effect is not considered in the method.Through the comparison between the traditional method and the improved Mindlin method,it can be found that the calculation values of the two methods are greatl y different in the range of near pile foundation,while the calculation results of the two methods are graduall y consistent in the range far from pile foundation,which conforms to the principle of st.venant of elastic mechanics.(2)Draw up sets of partition wall treatment programmes,through numerical simulation to stud y the influence of the depth,the thickness(stiffness),the longitudinal length of the wall processing line and the construction location on the treatment effect of the partition wall.The anal ysis results show that the partit ion wall between the right and the high speed railway subgrade position can effectivel y block the additional influence of new bridge pile foundation load on high-speed railway subgrade,the depth and the length of the wall are bigger,barrier effect is mor e obvious;barrier effect of wall thickness on high speed railway subgrade settlement,additional horizontal displacement the influence.(3)Based on an actual project,combined with test and numerical anal ysis results show: the new fl yover bridge load wi ll cause adjacent irrigation high speed railway subgrade greatl y exceed the specification allows additional settlemen t,subgrade settlement value of the total,at the same time,also will be foundation of high speed railway subgrade because of the addition al influence of horizontal stretch displacement,thus causing some a threat to the Chengguan high speed railway safet y and stability.Through the proposed isolation treatment scheme,finall y chose the combination of micro steel pipe pile and pile top beam: the method has small disturbance,low field requirement,the advantages of flexible operation and good partition eff ect,to ensure the normal operation of the overall stabilit y and high filling subgrade of the iron line. Ⅱ.Connecting condition:(1)Based on the case of bridge abutments being inclined and upright,the load of the inclined subgrade is divided,and the calculation formula of additional vertical stress of the subgrade behind the platform is extended to the case of an y inclined connection.(2)The role of abutment pile deformation impact is in the vertical direction b y CFG pile load transfer function change of dee p soft soil foundation settlement deformation characteristics of transition section reinforced foundation,in the horizontal di rection C FG lateral flow pile on soft soil has played a significant role in blocking.The effect of foundation reinforcement limi ts the creep characteristics of soil under subgrade loading to some extent.(3)The strength of saturated soft soil is very low,and when it is loaded,it will produce a great instantaneous settlement,and the top of the abutment will be inclined obviousl y towards the direction of the filling.In practical engineering of soft foundation preloading should be adopted to speed drainage and consolidation,and to reduce the instantaneous settlement and inclination of the abutment;It is proposed that the design method,such as variable pile spacing or pile length,should be adopted for foundation treatment of approach embankment,to str engthen t he control of settlement in near range back.(4)It is suggested that the convergence settlement value should be added to the design of the approach embankment.On the other hand,the inclination,and the direction of inclination are directl y re lated to the convergence settlement of the approach embankment,as well as the horizontal displacement of the piled abutment.