The Shear Theory And Experiment Research Of Pile Foundation Underpinning Based On The Truss-Arch Model

At present,the development of urban traffic is rapid,while the ground transportation and underground traffic in mutual reflection,work together to solve urban traffic congestion problems.The underground traffic has the advantages of fastness,comfortable and favorable environment,so the underground traffic became the first choice of most people.But in the process of underground traffic construction the problem of crossing the existing buildings has appeared inevitably.The pile underpinning is the most effective way to solve such problem.Subway has been constructed speedily in recent years,and the problem of crossing the existing buildings from below has appeared in the most underground tunnel excavation,the structure becoming more and more complex,including the high-rise building foundation and the complex bridge pile foundation.Technical method is the key to solve such problems,and the theoretical research also needs to be further discussed.In this paper,combined with the practical engineering of pile foundation underpinning,analysis of pile foundation underpinning project will be done,and bearing capacity of the connection between beam and pile caps will be researched.For the research content,the theoretical analysis and experimental analysis have been carried on.The main research contents are as follows:(1)Discussing the significance of the pile foundation underpinning,development situation and existing problems.According to the current situation of pile foundation underpinning research,the view that the theoretical system of pile foundation underpinning engineering is the key to solve the problem is put forward in recent years.(2)Discussing the principle of pile foundation underpinning,analyzing the process of transferring load in the process of pile foundation underpinning and underpinning principle.Based on a domestic building pile foundation underpinning engineering,combined with the engineering situation and essential point of underpinning structure,the underpinning plan for the project have been researched and analyzed.(3)Investigating the main factors of influencing the pile foundation underpinning structure shear ability,considering the effect of shear in various factors,shear mechanical model of underpinning structure is put forward based on the truss-arch model theory.Mainly analyzing the inclined section shear model,combined with previous theory and the personal analysis,come up with of shear formula of pile foundation underpinning structure.(4)Designing and manufacturing the part model of the connection between the underpinning beam and the pile caps is to make a test which includes shear ability and slip resistance in planting bar connection.Through researching the experimental phenomena and analyzing the experimental data,it is concluded that planting bar connection of shear performs well and the reliability of the mentioned formula is verified,so the research has certain reference value for the future.(5)Based on the above theory of shear performance of pile foundation underpinning and experimental research,utilizing finite element software to establish pile foundation underpinning structure prototype in the practical engineering,studying underpinning structure of deformation and stress in the process.It is concluded that the finite element analysis results coincide with the test results,the finite element analysis has a certain guiding role to the engineering practice.