Research On Key Technology Of Pipe Pile Foundation Pit Support

Pipe pile is used in foundation pit support because of its quick construction speed,environmental protection,short construction period,and has been paid more and more attention by engineers.This paper studies the key affected factors that affect the foundation pit support of pipe pile,such as adding core and connecting pile,etc.The main results are as follows:Firstly The research and development history of pipe pile at home and abroad and current situation of research on foundation pit support are expounded.Secondly,the design method and steps of pipe pile anchor support are introduced in detail,and several calculation methods of pipe pile bending bearing capacity,crack resistance bearing capacity and shear bearing capacity are analyzed.This paper introduces the failure form of pile and anchor support and analyzes the causes of its failure.Thirdly,the numerical simulation analysis of pipe pile used in foundation pit support based on FLAC3 D shows that with the increase of excavation depth,the horizontal displacement of pipe pile body increases,the intermediate deformation becomes larger and larger,the shear force and bending moment increase with the excavation depth.The maximum value is increasing and the position of maximum value is gradually moving downward.Through the comparison of pipe pile and same diameter cast-in-place pile anchor support it is found that the support performance of high strength concrete pipe pile is better than that of cast-in-place pile.Fourthly,the numerical simulation analysis of the key technology of pipe pile applied in foundation pit support shows that the displacement of pipe pile body andthe maximum tension and compression stress of pipe pile body are greater than those of cored pipe pile with the same excavation depth.From top to bottom,it is found that when the length of core is increased,the displacement of pile top decreases continuously.When the core is added to the bottom of the pile under the excavating surface,the effect of core addition on reducing the horizontal displacement of the pile top is not significant.From bottom to top,it is found that the maximum horizontal displacement of the pile top decreases with the increase of the length of the core,but it is not effective to reduce the maximum horizontal displacement of the pile when the core is added to the top of the pile.Core in different positions,It is found that the best effect is to add core to the excavated surface.The effect of increasing the elastic modulus of core-added concrete on reducing the maximum horizontal displacement of the cantilever supporting pile top and the tensile and compressive stress of the pile body is not obvious and the efficiency is low.The height of soil plug has little effect on the maximum horizontal displacement and pile stress of pipe pile cantilever support.The result is better when the position of pile connection is located near the end of the pile or far below the excavating surface.