Application Of Underground Continuous Wall With Concealed Column And Construction Key Technology Research

With the extensive excavation of deep and large foundation pits,the application of underground continuous walls is increasing.The foundation pit excavation project of Nanjing Ninghai Road adopts a two-walled underground continuous wall structure.The underground continuous wall is used as both the enclosure structure and the basement outdoor wall.In order to increase the joint stiffness of the diaphragm wall and the frame beam,and prevent the concrete cracking of the basement beam wall joints,causing hidden dangers such as water seepage,an innovative construction technique combining concealed columns and diaphragm walls is used.Concealed columns have been widely used in shear walls to resist the out-of-plane bending moments of beam-wall nodes,improve node stiffness,and prevent premature cracking of nodes.At present,the research on concealed columns to improve the joint stiffness of beams and walls has been mature,but there are few applied researches on the application of concealed columns in the underground continuous wall to improve the retaining capacity of the underground continuous wall.In this paper,the application of concealed columns to improve the retaining capacity of underground continuous walls during the excavation of foundation pits and the key technologies for the construction of underground continuous walls with concealed columns are studied.(1)Through the finite element simulation of the top-down method of foundation pit excavation,it is concluded that the underground diaphragm wall with concealed columns reduces the lateral displacement of the wall during the excavation of the foundation pit.With the increase of the excavation depth of the foundation pit,the The column has an enhanced ability to control the lateral displacement of the wall;the load acting on the underground continuous wall is mainly borne by the concealed column and transmitted downwards.The concealed column has a good restraint effect on the stress spread of the wall;relative to the one without the concealed column Diaphragm wall,the wall stress value of the diaphragm wall with concealed columns is smaller,and the wall deformation is more uniform.(2)According to the actual engineering situation,the finite element analysis was carried out on the groove formation of the irregular diaphragm wall.The result showed that the horizontal displacement at the external corner was greater than the displacement at both ends of the groove section;Tank depth: When the mud weight is between 11 k N/m3-12 k N/m3,the horizontal displacement of the tank wall decreases as the mud weight increases.(3)Research on the fabrication,reinforcement and hoisting of the underground diaphragm wall reinforcement cage with steel concealed columns.Through theoretical numerical calculation and ABAQUS finite element simulation analysis,the difference in shear force,bending moment,stress and displacement between the reinforcement cage with concealed steel column and the ordinary reinforcement cage during the hoisting process is compared,and the law is summarized according to the results,and the position of the lifting point is changed.Optimize the hoisting plan of the reinforcement cage with concealed column.