Numerical Simulation Analysis Of Reinforcement Effects Of Skirt Border Improvement For A Soft Soil Foundation Pit In Zhuhai

The skirt border improvement in the passive zone of the deep foundation pit can significantly increase the lateral resistances,reduce deformations of the foundation pit and the influence of the surrounding environment caused by the excavation,which has been widely used in the deep excavation engineering in Zhuhai.So it is an important topic to reasonably determine the reinforcement scheme,which can not only help to control large deformations of foundation pit and surrounding soil,but also ensure the economy of the project.Mainly based on the finite element simulation platform,Midas-GTS,several three-dimensional excavation models are established to analyze the reinforcement effects of skirt border improvement.At the same time,the optimal reinforcement scheme is analyzed.In order to ensure the accuracy and validity of numerical analysis results,Firstly,based on theoretical analysis,literature research and numerical model calculations,constitutive models of soil refer to foundation pit excavation are compared and selected.And then,based on the measured data,the soil stiffness parameters are determined by numerical back analysis.?1?The typical stress-path in soil induced by deep excavation has been analyzed.And combined with literature research,the deformation characteristics of soil under the stress-path of excavation are clarified.Then,based on the qualitative analysis of the applicability of three constitutive models in the calculation of foundation pit excavation and the comparative analysis of the calculation results of two-dimensional foundation pit,MMC is more suitable to be used in numerical analysis of deep excavation.?2?Based on the engineering case,28 numerical calculation models of three-dimensional foundation pit are established,and then based on range analysis and variance analysis,E₅₀^ref has a significant effect on the lateral deformation of retaining pile and the uplift deformation of pit bottom,and the influence of E_ur^ref on the deformation of the surface settlement outside the pit is significant.Finally,combined with the back analysis of the measured deformation data of the project,the suitable stiffness parameters of soft soil in Hengqin is E_oed^ref =1.0E_s1-2 ?E₅₀^ref =1.2E_oed^ref? E_ur^ref=7.0E₅₀^ref,which can get better simulation results.?3?The establishment process of three-dimensional foundation pit calculation model is introduced in detail,and 25 calculation models of excavation with different reinforcement conditions of skirt border improvement are established.By the analysis of the lateral deformation of retaining pile and the deformation of the surface outside the pit as well as the deformation of the deep soil outside the pit,it is concluded that the depth parameter of the reinforcement of the skirt border improvement has the most significant influence on the deformations of the foundation pit,and the maximum lateral deformation of the retaining pile is the most controlled.The optimal reinforcement depth of foundation pit can be 5H/12,and the optimal reinforcement width is H/2,and this scheme can provide some reference for similar deep excavation in Zhuhai.