Structure Optimization Of Deep Foundation About Pit Anchor Support Based On FLAC3D Simulation

As a temporary workshop,the supporting system of deep foundation pit not only meets t he requirements of safety and practicality,but also takes into account the cost.In order to mee t the safety requirements and minimize costs,it is more important for the research and optimiz ation design of supporting structures.In this paper,a project in Beijing as the research background,Through the collation and analysis of field measurement data,Combined with FLAC3D software for simulation analysis.The following conclusions are mainly drawn:（1）Firstly,some parameters of the model are studied,such as the stiffness of the bolt and soil joint in the model.The setting of the connection stiffness between the three sections of the bolt,the free end and the anchor section,after many simulations and comparisons in the model,the distribution ratio of the force on the bolt is similar to that of the actual situation when the stiffness between the end and the anchor section to the soil is set in the order of10⁷-10⁸.In addition,when the stiffness of anchor and soil connection is set to 10⁵N/m,it can be seen from the cloud chart that the axial force of the bolt is passing too fast to the end.When the connection stiffness is 10⁷N/m,the force is concentrated in the first two thirds of the bolt,both of which are unreasonable.It is concluded that the connection stiffness of the bolt end,free end and anchor section is 10¹³N/m,1N/m and 10⁶N/m respectively.（2）The horizontal displacement of the lateral wall of the foundation pit is medium and small.（3）Reasonable decorate the position of the anchor rod can effectively reduce the deformation of the foundation pit wall,the reasonable arrangement of the anchor position can effectively reduce the deformation of the soil in the foundation pit.Compared with the original model,the maximum displacement of the foundation pit decreases by 3mm when the third and fourth floor bolts are moved up to 250mm at the same time.When the two layers of anchor are moved up to 520mm,about 5mm is reduced,and the maximum horizontal displacement of the lateral wall of the foundation pit can be reduced without changing the project cost,and the security of the supporting structure.（4）The deformation of foundation pit decreases with the length of anchor rod and pile diameter.In the simulation,the anchor length is reduced by 2m,and the maximum displacement of the lateral wall of the foundation pit has not changed significantly.The pile diameter decreased to 700mm,and the maximum lateral wall displacement increased by about2mm,without affecting the normal use of the supporting structure.Therefore,under the premise of ensuring the safety of the project,we can choose the right size and save the project cost.（5）In addition,the foundation pile has a great influence on the stress deformation of the supporting structure.The existence of pile foundation can increase the pressure of passive earth,so as to lower the bending point and effectively reduce the maximum displacement of the lateral wall of the foundation pit.