Research On The Influence Of The Rigidity And Position Of Uplift Pile On The Bearing Characteristics Of The Main Structure Of Subway Station

Uplift piles are often used to solve the problem of insufficient anti-floating of urban underground projects such as subway stations,underground parking lots,underground commercial,and municipal tunnels.In the engineering practice,uplift piles can be improved in addition to making up for insufficient anti-floating measures.Internal force distribution of structure and control of structural deformation.At present,the research on pile foundations mainly focuses on the bearing capacity and deformation characteristics of piles.In structural calculations,how to perform simplified simulations against piles and how to accurately simulate the restraint of piles can make the calculation results closer to the engineering practice,when the uplift piles are arranged under the structural floor,how the pile positions should be arranged can make the uplift piles play the most effective role.The above is the main problem to be solved in this article.In this paper,the simplified model of uplift pile is studied and compared,and the constraint action of uplift pile is simulated by large stiffness spring.The axial spring stiffness value of uplift pile is calculated by P-S curve of pile.Using Midas GTS to simulate the process of single pile uplift and comparing it with the test pile results,it was found that Midas GTS can more accurately simulate the uplift of the uplift pile.On this basis,using Midas GTS to analyze the influencing factors that may affect the P-S curve and axial stiffness of the uplift pile,the study found that the factors affecting the bearing capacity of the uplift pile are mainly the pile diameter,the pile length,and the side friction of the soil around the pile.Resistance;The factors that affect the displacement of the top of the uplift pile are the pile diameter,the length of the pile,the elastic modulus of the soil,and the side friction resistance of the soil around the pile,while the elastic modulus of the pile The influence of the uplift displacement is small;the axial stiffness of the uplift pile is a value that changes continuously with the uplift load and uplift displacement.The factors affecting the axial stiffness of the uplift pile are mainly the pile diameter,pile length,and the elastic modulus of soil.,while the elastic modulus of the pile,and the side friction resistance of the soil around the pile have relatively little effect on the stiffness.After obtaining the axial rigidity of the uplift piles,this paper relies on a subway project in Suzhou,based on the actual structure and soil parameters,and uses SAP2000 to establish a three-dimensional calculation model of the subway station with uplift piles.The internal force and deformation of the structure under the pile-up stiffness are analyzed.It is found that the setting of the pile-up resistance can effectively control the vertical deformation of the structure and improve the internal force distribution of the structure.The more obvious the distribution improvement effect,the more resistance the uplift pile needs to provide,but when a certain spring stiffness value is reached,the increase in the adjustment effect of the uplift pile is decreasing.Using SAP2000 to establish a three-dimensional calculation model of a subway station,the research on the setting of the pile position of single-column double-span and double-column three-span subway stations was carried out.For single-column and double-span stations,it is recommended to set up the pile positions under the bottom longitudinal beam,and the uniform arrangement of the uplift piles in the column span is better than the effect under the column.When the uplift piles cannot be arranged under the bottom longitudinal beam,it should be set as close as possible to the bottom longitudinal beam.For two-column and three-span stations,the uplift piles can be placed under or between the longitudinal beams,which can effectively reduce the vertical deformation of the station structure and adjust the bending moment distribution of the slab walls and longitudinal beams.At the midpoint of the cross section(where the structural deformation is the largest),it is most effective in controlling the vertical deformation of the structure and reducing the mid-span and mid-span bending moment of the structure.When the uplift pile is placed under the longitudinal beam,it reduces the bending of the bottom longitudinal beam.Moments are most effective.