Design And Numerical Simulation Of Pile-anchor Supporting Structure After Deepening Of Existing Construction Pit

The design requirements of supporting structure are very strict after the temporary deepening of pile-anchor support construction foundation pit,and many supporting design forms are not suitable under the restriction of surrounding environment of foundation pit,so it is of great significance to study the design of supporting structure after temporary deepening of foundation pit.On the basis of previous studies and combined with field engineering examples,this paper systematically studies the design of supporting structure and the deformation of surrounding buildings after foundation pit deepening by using the method of combining rational calculation and numerical simulation.The specific research work has the following aspects:(1)The design of the support before and after the deepening of the foundation pit is researched through the software,and checked the stability of the supporting structure before deepening the foundation pit,and analyzed the influence of the new support structure on the old support structure.It is found that the new support has little impact on the existing support.Consider the upper soil mass of the newly added supporting structure as a uniformly distributed load,calculated the support design after the change.The calculation shows that the support design meets the safety requirements after the change.(2)The eight working conditions before and after deepening of the foundation pit were numerically simulated using geotechnical engineering software.Combining the comparison of the two cross-sections,each working condition is analyzed.In the first five working conditions,the soil displacement,the axial force of the anchor rod and the bending moment of the pile body were analyzed respectively,and the deformation characteristics of the foundation pit excavation before the deepening of the foundation pit were obtained;In the last three working conditions,the soil displacement,soil stress,anchor rod axial force,pile bending moment and slope top building were analyzed,and the deformation characteristics of the foundation pit excavation process after the design change were obtained.(3)Simulation software was used to model the columns,ring beams,doors and windows of the independent basic frame structure on the top of the foundation pit in detail.The deformation of the building during the construction process after the deepening of the foundation pit is analyzed,and the deformation law of the building frame structure,the internal force of the frame structure and the main tensile strain of the north longitudinal wall of the building are obtained.The vertical and horizontal displacements of the soil at the bottom of the building and the north of the building are analyzed,and the displacement curve of the soil at the top of the foundation pit is obtained.(4)To further study the supporting effect of the front and rear supporting structures of deepening the foundation pit.The analysis was carried out in combination with the on-site monitoring data and the results of numerical analysis.Analysis shows: The design of the supporting structure after the deepening of the foundation pit can meet the changed supporting force requirements,and both the horizontal and vertical displacement of the soil conform to the requirements of the specification.