Study On Bearing Behavior Of New Special-shaped Vertical Reinforcement Composite Foundation

The Infrastructure construction has been developing by leaps and bounds in China.In the process of construction,poor foundation conditions,such as soft soil foundation,are often encountered.However,high requirements of bearing capacity and settlement of foundation are often put forward in new constructions.Therefore,it is high time that soft soil foundation improvement should be an emphasis of Chinese constructions.Composite foundation is widely used in construction,highway,railway subgrade and hydropower foundation treatment engineering because of its simple technology,convenient construction and low cost.Accordingly,based on this,three new methods of foundation reinforcement,Junked Tires Encased Slags Pile Composite Foundation,Hexagonal-section Composite Foundation,Grid-Shaped Diaphragm Composite Foundation,has been proposed.Generally,this thesis mainly focused on the analysis of load-settlement characteristics and load-transfer mechanism of the equivalent reinforcement range of those new special-shaped vertical reinforcement composite foundation under vertical load.Then,a series of model tests and numerical simulations were conducted to investigate the variation law and influencing factors of load and settlement under vertical load.The calculation method had presented for the settlement analysis of new special-shaped vertical reinforcement composite foundation.It was based on elastic theory and assumed load-transfer function.The main work and results are as follows,(1)To clarify the load-settlement characteristics and load-transfer mechanism of the equivalent reinforcement range of single pile composite foundation,the laboratory-scale model studies on bearing characteristics of junked tires encased slags pile composite foundation,trilobal pile composite foundation and“#”shaped structure were carried out.The test contents were to measure the overall settlement of the composite foundation,the stress-strain of the reinforcement and soil.(2)Using the finite element software PLAXIS~3DD to verification and exploration those load-settlement characteristics and load-transfer mechanism,which included the pile-soil stress ratio,the axial force,the side friction resistance and the end resistance of the reinforcement.The finite element model of composite foundation with the same proportion as the laboratory-scale model test had been established,and the ultimate bearing characteristics of the equivalent reinforcement area of three new types of special-shaped vertical reinforcement composite foundation were verified and explored.(3)Based on the analysis of the results of model test and finite element numerical simulation,a calculation model was established to analyze the load-settlement relationship of each composite foundation according to Hooke’s law and the conditions of vertical force balance of micro segments.Good agreement between the measured and calculated results was achieved,which demonstrated the reasonability and effectiveness of the proposed calculation method,and provided a useful reference for the further development and optimization of the three new types of special-shaped vertical reinforcement composite foundation in the future.