On Rule Of Deformation And Optimization Countermeasure Of Deep Foundation Pit Excavation Support Construction

Along the further advancement of urbanization,the construction of foundation pits and the continuous improvement of urban building density put forward higher requirements concerning safety issues.Foundation pit excavation results in a certain degree of ground displacement under different stresses,which in turn exerts influence on the stability of the foundation pit.The physical and mechanical properties of the ground vary in different places,which differentiates the foundation pits.In this paper,Hangzhou “L” type foundation pit project is taken as a case study,and the supporting system of bored pile and reinforced concrete internal support is introduced.The mechanism of foundation pit excavation process and the possible deformation of foundation pit enclosure are carried out on a theoretical basis.The on-site monitoring data during the excavation of the foundation pit and the stress of the foundation pit are analyzed by measuring the horizontal displacement of the soil at the monitoring point.The engineering is modeled by PLAXIS by simulating the construction strategies of foundation pit excavation,comparing the calculation analysis with the on-site monitoring data,analyzing the skirting deformation and its cause on the enclosure support,and testing the reinforcement scheme of the skirting.The major conclusions of this paper are as follows:(1)PLAXIS is applied to model the foundation pit concerning the engineering project,simulate the construction strategies of its excavation,and analyze and compare the data with the monitoring data.The results show the similarities of the simulated calculation data and the measured data.It conforms to the variation law of foundation pit deformation,which indicates that the model and calculation method are reliable,and the PLAXIS numerical simulation can reflect the law of foundation pit excavation.(2)The finite element simulation of PLAXIS shows that the horizontal displacement of the enclosure supports with the skirting deformation is trapezoidal from the bottom up.The reinforcement scheme should focus on the bottom.After reinforcing the skirting of the foundation pit,the maximum horizontal displacement is reduced from100 mm to 40 mm,which is less than the warning value,indicating that the reinforcement scheme can effectively prevent the deformation of the foundation pit.(3)The depth of the foundation pit enclosure supports directly determines the stability of the foundation pit.From the perspective of cost-effectiveness and safety,the optimal depth of the supports is 2 meters.The research results provide reference for foundation pit protection and excavation under similar conditions.(4)Multi-group numerical simulation of different pile lengths in the foundation reinforcement area is carried out by PLAXIS,the stability of different pile length foundation pits is compared and analyzed,and the optimal scheme is obtained.Engineering practice shows that the scheme effectively ensures the cost-effectiveness and the stability of the foundation pit.