| As the project quality requirements become more advanced,the foundation pit support design is shifted from stability control to deformation control.Nevertheless,for foundation pit design,there is a lack of consideration for the time effect of deformation,which will gradually increase with time and gradually decrease in stability.Among which the creep deformation of the soil is the main part that leads to the continuous deformation of the foundation pit.Relying on the foundation pit project of Xi’an High-tech Conference Center II.This paper firstly introduces the design and monitoring scheme of the foundation pit support,and analyzes it in accordance with the monitoring data.Then,using Abaqus CAE builds infinite element model and construct Particle Swarm Optimization algorithm to invert the parameters of soil creep function.The inversion results are substituted into the model to verify and analyze the deformation of foundation pit support structure under creep effect.Further analysis of the influence law of building load and support structure parameters on the deformation of the support structure based on this model.The results show that.Combined with the actual monitoring data,the deformation of this foundation pit meets the construction control requirements.Among them,the deformation of the foundation pit is larger in the excavation stage,and the deformation continues to occur after the end of excavation.The deformation of about 1 year after construction occupies 30% of the whole deformation,which is more apparent,indicating that the pit deformation has creep effect.Based on the measured displacement data,the PSO algorithm can be used to optimize the inversion of geotechnical parameters,and the fit of the inversion results is high.Combined with the model analysis,it can be seen that: the creep effect of the soil will continue to increase the pile displacement,deep soil lateral displacement,and surface settlement during the long-term exposure stage after the excavation of the foundation pit is completed,while the impact on the base uplift is minor.Among them,the displacement of supporting pile body develops from medium convex type to cantilever type.The horizontal displacement at the top of supporting pile is the maximum value of overall deformation,so the horizontal displacement at the top of supporting pile is elected as the control index of foundation pit deformation analysis.The ground load value,load distance,support pile diameter,pile spacing and embedment ratio,and anchor cable prestress value were taken into account for impact analysis.The analysis results are: The magnitude and spacing of ground loads have a significant effect on foundation pit deformation,and it is recommended to maintain a distance from the excavation edge of at least twice the excavation depth.To mitigate pit deformation,support design should consider increasing pile diameter,embedment ratio,anchor prestressing,and reducing pile spacing.But there is a certain threshold value,exceeding which the effect will be weakened.The best support effect is when the embedment ratio of the support pile is 0.35,the setting of pile spacing should not be too small either.The creep effect of soil will have an amplifying effect on the pit deformation under different support conditions,mainly manifested as a power exponential amplification of the pit deformation in the accelerated creep stage and a weakening amplifying effect in the stable creep stage. |
