Research On The Modeling Method And Mechanical Properties For The Key Parts Of Pile-slab Subgrade

Pile-slab roadbed was first used in railway engineering,and its application in highway engineering has been gradually started in recent years.The pile-slab subgrade is a kind of supporting structure system formed by the combination of precast slab highstrength concrete pipe piles and the connection parts of the pile-slab subgrade,which is more similar to a special bridge in the practice of highway pile-slab subgrade.Pileslab subgrade has the advantage of high stiffness and smoothness,good postconstruction settlement and small settlement,which is suitable for assembly operation.Due to the lack of application of pile-slab subgrade in highway engineering,the modeling and calculation methods for reference are scarce.Therefore,it is necessary to study the mechanical behavior of this type of structure,and make special study on the key parts of the structure,so as to ensure the operation safety of the structure.Based on the above reasons,this paper studies the stress and fatigue problems of the joint parts of pile and plate with the beam element modeling method and multi-scale modeling method based on a highway pile and plate subgrade project.The main research work and conclusions of this paper are as follows.(1)Based on the support project,the beam element modeling method of highway pile-slab subgrade is studied.Beam element is used to simulate pipe pile,plate and shell element is used to simulate panel,and spring element is used to simulate pile-soil interaction.It is found that the beam element model can reflect the overall mechanical performance of the pile-slab subgrade structure,but can not reflect the detailed stress state of the pile board connection.(2)Based on the beam element model,the mechanical properties of the roadbed under various load combinations are studied.The most unfavorable stress state of the joint parts of the pipe pile and the pile plate is extracted and it is found that the joint parts of the pile-slab subgrade are the key parts of the subgrade stress of the pile-slab subgrade.The safety of the joint of pile-slab subgrade controls the overall safety of the structure.(3)By introducing the idea of multi-scale modeling,the multi-scale model of highway pile-slab subgrade is established.The model can not only consider the overall performance of the structure,but also reflect the details of the joint parts of the pileslab subgrade.The multi-scale model can not only greatly reduce the calculation unit and improve the calculation efficiency,but also accurately describe the stress details of the pile plate connection.(4)Based on the multi-scale modeling method and model,the stress of steel reinforcement stress plate and the spatial stress state of non-shrinking concrete are studied in the two design schemes of the pile-slab subgrade connection part of the project.At the same time,the fatigue performance of the two schemes was studied.