Application Research Of Steel Tube Pile Support Technology In Shallow Buried Tunnel Engineering In Urban Complex Environment

With the acceleration of urbanization,the development and application of underground space has gradually become the focus of urban research.As most construction sites are located in densely populated and important traffic sections,higher requirements are put forward for construction duration and construction technology.Micro pile is a supporting form of row pile with a diameter of about 70~300mm.When the excavation depth is large and the deformation requirements are strict,the supporting system of micro steel pipe pile can be used together with other supporting forms.Due to its advantages such as fast construction speed and small impact on the surrounding environment,it is widely used in foundation pit,slope and other protection projects.For different geological conditions and engineering requirements,steel pipe pile supporting effect is not entirely consistent,therefore this paper,taking a shallow depth excavation tunnel project of jinan as the backing,discusses the micro steel pipe piles in urban complex environment supporting effect,the study mainly from the following aspects:(1)Understanding of steel pipe pile research status at home and abroad,to summarize the application of steel pipe pile;(2)Theoretical analysis of single row steel pipe pile and double row steel pipe is carried out,and the finite element software MIDAS/GTS is used for the simulation of two-dimensional calculation examples,so as to verify the relationship between finite element simulation and theoretical calculation;(3)The three-dimensional finite element calculation model was established to analyze the similarities and differences of the supporting effects of single row steel pipe piles and double row steel pipe piles,and to compare the changing rules of double row steel pipe piles under different pile spacing and wall thickness.(4)To study the supporting characteristics of miniature steel pipe piles in the process of supporting the shaft foundation pit of shallow buried tunnel and the end wall reinforcement,and to analyze the deformation law of steel pipe piles and soil.Through analysis,it is concluded that in the complex case of shallow excavation in the city,the displacement of the shaft foundation pit supported by double-row steel pipe piles withconnecting beams is nearly 30% smaller than that of single-row steel pipe piles.Under the premise that pile diameter and row spacing remain unchanged,it is reasonable to set the pile spacing at 2 times of pile diameter,and the influence of steel pipe pile wall thickness on the stability of the foundation pit is limited.Double row steel pipe pile in shallow depth excavation tunnel cross channel end wall support,steel pipe pile composite supporting system is subject to the flexible support,but in the normal viscous soil layer can better control the horizontal displacement of soil,such as increasing vertical supporting stiffness,with double row of steel pipe pile can reduce the horizontal displacement of about 31%,make the horizontal hole end soil more stable.