Application Research Of Foundation Pit Supporting With Top-down Method In Underground Garage

With the rapid development of economy and the rapid increase in the number of private cars,the construction of underground garage has become the most effective way to solve the crowded problem of the residential quarters.The retaining structure of foundation pit that is located in the the residential district or the busy area of the city whose surrounding environment is complex and construction space is limitted,which is designed not only meet the the requirements of the strength,but also satisfy the demand of the deformaton to ensure the important facilities and the the existing buildings around the foundation pit safe.The top-down method is a new construction technique in deep excavation,which can effectively reduce the impact of excavation on the surrounding environment and reduce the cost and construction period.By using the finite element software ABAQUS to establish three-dimensional model,the paper analyse the internal force of retaining structure,the deformation of the foundation pit and the effect on the adjacent buildings in the different excavating condition,which is based on the increased he underground garage.The main work and results are as follows:(1)Acconding to the fundamental theory of the reverse construction method,the extetior-ptotected construction,the vertical support system,the lateral bracing structure and the connection of the node position are introduced and expounded.(2)The results are demonstrated:the bending moment of the pile and the axial force of the supporting columns are analysed in the reverse construction.The bigger bending moment is beared by the pile in the excavation of the foundation pit,at the same time,the foundation pit is closer to the foundation pit,the greater influence on the pile arrangement.The column has been under balanced pressure.(3)Through analysing the performance of the surface displacement outside foundation pit,the horizontal deformation of the piles,displacement of the buttom foundation pit and vertical displacement of foundation,the resuts are follows:the two sides soillayer and the arrounding surface of the foundation pit are moved to the foundation pit,furthermore,the position of the maximum settlement occurs in a certain distance from the edge of the pit.With the movement of the soil,both sides of the foundation pit are inclined to the foundation pit.(4)By changing the diameter,spacing and the embedment depth of the pile on the effect of the displacement,the conclusion is that the increasing diameter and the embedment depth of the pile or the reduction of the pile spacing can reduce the horizontal deformation of the foundation pit and the settlement of the surrounding surface,but in the case of meeting the needs of the project,constantly increasing the pile diameter and the embedded depth or reducing the pile spacing can weaken the effect on the deformation of the foundation pit gradually.