The Common Foundation Pit Of "Pile-anchor-strut Bracing" Deformation Research And Application

Along with our country accelerating the process to city,more and more deep excavation engineering are appearing in the dense buildings and the complicated environment in the city,in order to reduce effect of buildings,underground pipelines and municipal facilities,in order to ensure the safety and stability of foundation pit,the foundation pit deformation must be controlled.Considering foundation pit surrounding environment and economic factors,single supporting method has been unable to satisfy the needs of foundation pit engineering,various supporting methods of foundation pit engineering be widely used in common,"pile-anchor-strut bracing" common foundation absorbs the pile anchor foundation pit advantages and pile strut bracing foundation pit advantages,it has been applied to the design of deep foundation project.At present,the theory of "pile-anchor-strut bracing" is imperfect in the design of foundation pit supporting,and it lacks of construction experience.In the actual engineering design,the design is blind,and the construction measures are ineffective.In this paper,the finite element numerical simulation method is used to compare the support scheme,and the optimization of the design parameters of the foundation pit has a certain guiding significance for the rational design of foundation pit engineering.In this paper,the finite element simulation software MIDAS/NX as a platform,"pile-anchor-strut bracing" common foundation pit engineering project in Dezhou as the background,using the finite element simulates the excavation process,following are research contents and main results:(1)The pile anchor and pile strut bracing common supporting structure utilize active support and passive support types,and the pile anchor and pile strut bracing common supporting structure use flexible and rigid supporting types together,using of pile strut bracing type to control the deformation of foundation pit effect is good,does not occuping the foundation of outer space resources.The pile anchor support does not occupy the internal space of the foundation pit,and the excavation is convenient.According to the difference of the surrounding environment,the different supporting forms can be flexibly determined.(2)Using MIDAS/NX three-dimensional numerical simulation software to analyze the deformation characteristics of the pile anchor and pile strut bracing,and comparing thesupport scheme.Considering the buildings of North side near the foundation pit,on deformation control of high requirements should adopt the pile strut bracing type,the west side of the foundation pit is wide open space,therefore choice the pile anchor supporting structure.Considering safe,technical and economic factors,through scheme selection,so deciding to use "pile-anchor-strut bracing" structure of common foundation pit.(3)the use of MIDAS/NX on the deformation of "pile-anchor-strut bracing" common foundation pit was studied,the supporting pile diameter,embedded depth of supporting pile,prestressed anchor,anchor angle,internal support section area have a significant effect on the displacement of retaining structure,and then use the orthogonal method to support optimization of supporting scheme.The range analysis of the orthogonal test is carried out to ensure the safety and stability of the foundation pit,and the engineering cost is taken into account,the most reasonable design parameters of the supporting project.(4)Based on the project example and monitoring on the construction site,the common foundation pit "pile-anchor-strut bracing" analysis of the actual monitoring process,the numerical simulation results and the actual monitoring results were analyzed,the basic value fitting and monitoring value of numerical simulation,the reliability of the model is proved reasonable and the numerical simulation results.(5)Through the comparison of the engineering pile support structure and "pile-anchor-strut bracing" common supporting structure the cost,in order to meet the safety of foundation pit and deformation control,"pile-anchor-strut bracing" common supporting structure than the pile support greatly save construction cost,it has good economic benefits.