Study On The Influence Of Complex Excavation On Piles In Land And Seabed Using Numerical Simulation

The excavation of the tunnel is usually carried out in the vicinity of the existing piles during the reconstruction of urban rapid road,which may affect the safety of the piles.In this paper,the excavation of Shenzhen Haibin Tunnel is taken as the engineering background,and the numerical simulation method is adopted to solve the engineering problems of open-pit excavation in land and seabed.Considering the safety,construction convenience and economy of pit and adjacent bridge piles,the optimal selection of the cofferdam with double-row steel sheet pile and membrane bag sand combined with steel sheet pile impermeable core wall cofferdam is made.The influence of large-scale excavation of complex excavation on the stability of adjacent existing bridge piles.The main technical difficulties of numerical simulation are as follows: the sand simulation method of membrane bag by introducing the contact element between membrane bags;The necessity of a large-scale numerical model for the influence of foundation pit excavation on adjacent multi-span bridge piles.Research achievements include:Firstly,in the process of numerical simulation of excavation in seabed,the previous method of numerical simulation of membrane bagged sand cofferdam was improved.In this paper,elastic constitutive method is used to simulate bags.Goodman element without thickness was used to simulate the contact between bag and bag's interface.The feasibility of this method was verified after comparison between numerical simulation and model test.Secondly,optimize double row steel sheet pile cofferdam and membrane bagged sand combined with steel sheet pile impermeable core wall cofferdam form.Two kinds of cofferdam structure are stable.They are similar by contrasting the underground-continuous-wall's displacement.Because the stability of pile foundation is better and cofferdam construction cost is lower,film bag of sand cofferdam structure is better than the double row of steel sheet pile cofferdam structure.Thirdly,based on the numerical model of multi-span pile foundation and single-span pile foundation,the disturbance caused by the excavation of the tunnel excavation is the main reason of the structural deformation of the bridge.The numerical simulation of multi-span pile foundation shows that the deformation of pile foundation is coordinated and the upper structure is not damaged.Because of the upper structure,the deformation of multi-span pile foundation is smaller than that by the single-span pile foundation modeling method.The deformation of multi-span pile foundation modeling method can provide a reference for the application of single-span pile foundation modeling method in future projects when the deformation of pile foundation exceeds the standard value.