Study On Interactions Of Pile-slab Structure And Subgrade Soil In Curved Section

Because of high smoothness of high-speed railway, the amounts of total settlement, post-construction settlement and differential settlement of the embankment and foundation are all strictly limited. The traditional design scheme is changing the roadbed program into bridge structure, substituting bridge for road. In contrast, the cost of the bridge is very high, moereover, the lateral stability of the bridge structure is poor, especially in the curved section.Based on this, a new type embankment named pile-slab embankment is widely used in the construction practice of high-speed railway non-ballasted track. This structure can give full play to the interaction among the pile, slab and soil,not only the settlement is lower,but also the applicability of pile-slab structure is better than bridge structure and traditional embankment in curved section. This paper combines with National Natural Science Foundation of China project’study on the interaction of pile,slab and subgrade soil of pile-slab structure in high-speed railway’, carries out in-depth research on the pile-slab structure in curved non-ballasted track section based on the comprehensive investigation of literatures, as follows in detail:(1) Based on independent pier-pillar pile-slab structure theory and practice, using the elastic foundation beam model, combining the interaction theory of pile,slab and soil, utilizing displacement method of structural mechanics, derives theoretical analytical formulas of pile-slab structure in the lateral direction under loads.The analytical formulas can more fully reflect the force deformation characteristics of the pile-slab structure and it is esay to master for designers.Furthermore,it has great significance for guiding the design and engineering practice of pile-slab structure.(2) Establish static and dynamic three-dimensional models of pile-slab structure in curved section with finite element software and verify the reliability of the model combined with the related static and dynamic test experiences.The conclusion shows that established models is reliable.(3) Study the similarities and differences of pile-slab structure under the vertical force in curved and straight section, analyze lateral restraint of the soil at pile side to the pile-slab structure; study the force and deformation laws of pile-slab structure under the temperature force in curved section. The conclusions show that:the contact properties of pile slab and soil have a certain impact on the force and deformation; pile-slab structure in the curved section under vertical force can lead to bending-torsional coupling effect, the smaller the curve radius, the more unfavorable of the force and deformation;the horizontal constraint of soil at pile side is relatively stronger than vertical; due to the effect of curve and superelevation, the pile-slab will have a warp and offset along the longitudinal and lateral directions under temperature load and temperature gradient load, futhermore, stress concentration will be generated on the solid junction of the pile and slab;the variable quantity of the force and deformation of the pile-slab structure under temperature force is very small, when the curve radius is more than5500m.(4) Explore the dynamic interaction characteristics of the high-speed railway pile-slab structure in curved section under different speeds, slab spans and subgrade supporting conditions. Concluded that:the higher the speed of the train pass through the curve, overall, the severer dynamic response will be;at the same time, the condition of offset load of vehicle will change correspondly; lateral acceleration of vehicle,wheel unloading rate and outer rail’s derailment coefficient are connected with unbalanced superelevation.If slab span increases, the structural displacement will become larger and the lateral acceleration of vehicle and wheel unloading rate will decrease, but the vertical acceleration of vehicle and derailment coefficient will increase.The subgrade supporting conditions have large influence on the dynamic performance of pile-slab structure.The deeper of soil disengaging under the bearing plate, the larger of the displacement of the whole structure and the worst of its lateral stability, so it is more unfavorable to the security and stability of train operation.(5) Analyze the vibration response of pile-slab structure under the periodic load.The conclusion shows that with the increase of load frequency,the deformation and stress of pile and slab is lower.However, when the load frequency is close to the lateral natural frequency of pile-slab structure,the structural response will be suddenly aggravated.