Numerical Analysis And Control Method Of Excavation Deformation In Deep Foundation Pit Engineering

In recent years,the development of urban construction has been toward higher levels,and the depth of excavation of foundation pits has been increasing.The form of foundation pit retaining structure has also become more and more complicated due to the diversity of engineering environments.The traditional methods for calculating the forces and deformations of retaining walls for excavation of foundation pits include the limit equilibrium method,the subgrade reaction method,and the finite element method.Among them,the finite element method has been developed rapidly and its application is maturing in recent years.At present,the analysis of the foundation pit support system mostly reduces the original three-dimensional problem to a one-dimensional or two-dimensional plane problem.Then,the finite element method based on one-dimensional Terzaghi consolidation theory or two-dimensional Biot consolidation theory is used for analysis.For a complex foundation pit support project,one-dimensional or two-dimensional simplification cannot fully reflect the condition of stress and deformation of the support system.It is even more difficult to fully reflect the affected conditions around the foundation pit and cannot meet the requirements of the current complex engineering.Based on the analysis of the stress and deformation under foundation pit excavation,a three-dimensional finite element analysis is carried out regarding the interaction of soil and the entire retaining system.Taking a deep excavation project in Shenzhen as the research object,a three-dimensional finite element model is established for numerical analysis using finite element software ABAQUS considering the role of dewatering and recharge.In this thesis,the important Parameter settings of the deep foundation pit numerical simulation and the key steps are introduced.The Mohr-Coulomb elastic-plastic constitutive model is used for soil and the contact element is used to simulate the interaction between the soil and supporting piles.The transient analysis is adopted to simulate the dewatering and the Model Change function is used to simulate the entireprocess of excavation and retaining.Through analysis,the internal forces and deformation distribution of the support system under different conditions,the distribution of earth pressure,the distribution of groundwater pressure,the uplift of the soil at the bottom of the foundation pit,and the sedimentation of the surrounding ground were presented.The results are comPared with that by the traditional methods and the actual monitoring values,and the deviation among these results are analyzed.The applicability and reliability of the three-dimensional finite element modeling was then verified.Finally,according to the analysis results,the project is summarized,and effective measures to control the stability of groundwater level around deep excavation are proposed,which may provide reference for the deep excavation engineering to reduce the effect of dewatering excavation on the surrounding environment.