Research On The Application Of Prestressed Tension String Beam Steel Support In Foundation Pit

In recent years,the domestic economy has fully grown quickly,and as a result,the amount of urbanization and building has hyperbolic,and the various pollution and waste generated in the construction process are becoming more and more serious,and the country began to vigorously advocate the development and promotion of green,low-carbon and energy-saving construction technologies.The engineering of foundation pits is a crucial element in the development of cities that cannot be overlooked,especially in today’s increasingly tight construction land and more stringent environmental protection,reducing the deformation of foundation pit and reducing the encircling environmental impact is that the future development direction of foundation pit engineering.Therefore,the prestressed tension string beam steel support system as an assembly,reusable,green environmental protection foundation pit support scheme has entered the sphere of vision of the domestic construction industry,and has begun to be applied to domestic deep foundation pit projects.To increase their dependability,applicability,and economy as well as to encourage the promotion and use of the system,there has to be more study on such support systems both domestically and internationally.Taking the actual case as the research object,PLAXIS 3D numerical sim ulation is employed to research the appliance impact of the web and numerous fact ors touching its performance,and the reliability is further verified by comparis on and analysis with the on-site monitoring data.Also,the "demolition memb er approach" is utilized to combine the redundancy calculation formula and as sess the support system’s resilience to continuous collapse.The following are t he paper’s primary conclusions:(1)In this paper,the PLAXIS 3D three-dimensional finite component model is employed to simulate and analyze all operating conditions in an exceedingly foundation pit project employing a prestressed beam string steel support system.The results of the analysis show that the vertical displacement of the column,the axial force of the inner column,and therefore the lifting of the mythical site floor are as high as the alert value,while most of the horizontal displacement of the column and therefore the maximum settlement displacement of the floor are 21.1 mm and 22.34 mm,respectively,which also fail to meet the alarm standard,indicating that the foundation pit has been in a safe state,The PLAXIS 3D analysis results prove that the system is scientific and reliable.(2)This article has twice improved the values of three indicators in the PLAXIS3 D model: steel support prestress,diameter of retaining piles,and embedded depth of retaining piles.The simulation analysis shows that adjusting the diameter of the retaining piles has a significant effect on the deformation of the foundation pit,reducing the horizontal displacement of the retaining structure by 36.35% and17.75%,respectively,From the above data,it can also be found that after increasing the model parameters to a certain extent,the corresponding reduction in foundation pit deformation decreases,while the engineering cost continues to increase and the cost performance ratio decreases.Therefore,in the design stage of foundation pit support,factors such as foundation pit safety,environmental impact,and cost should be comprehensively considered to avoid waste.(3)By setting observation points inside the excavation to obtain the measured information of various indicators of the excavation deformation,and comparing and analysing with the PLAXIS 3D simulation value,it can be seen that the deviation range between the monitoring value and the simulation value is 6.5% to 17.85%,and the trend of change is basically consistent.Both data do not meet the alarm value,meeting the specifications and design requirements.The data measured on site not only proves once again the reliability of the support system,but also shows that the simulation effect of the PLAXIS 3D finite element model is appropriate for the particular situation and can provide scientific and affordable information support for the longer-term support structure style of foundation engineering and also for the surrounding environmental impact assessment.(4)In this paper,the "component removal method" and the redundancy calculation formula are used to evaluate the resistance to continuous collapse of the prestressed beam string steel support system,and t The deformation and internal force changes of the support system when most of the parts fail are analysed by PLAXIS 3D simulation.The evaluation results show that the redundancy of the lower internal support is significantly smaller than that of the upper internal support directly above the same position,and the redundancy of the diagonal strut is lower than that of the angle strut and also than that of the steel rod of the beam string.Especially,after the second diagonal brace fails,the stiffness redundancy and strength redundancy of the support structure are only 1.05 and 0.96.Therefore,in the design stage,the design requirements for the inner support and brace of the lower layer should be appropriately strengthened to improve the ability of the support structure to resist continuous collapse.