Numerical Simulation With FEM On Deep Foundation Excavation And Timbering Of Metro Station

Deep foundation pit engineering is one of hot and difficult problems in rock soil engineering. How to effectively control deformation of foundation pit and make foundation pit engineering safe and economical is the task that people always probe. Deformation for retaining structure of foundation pit is an important factor for effect on the deformation of foundation pit. On the basis of reading lots of relevant researches at home and abroad and summarizing former research achievement, in view of displacement, deformation and earth pressure behavior of pit-retaining structure during the processing of deep foundation excavations, analyses of calculating method for excavation by steps and practical engineering measurement have been finished, on the ground of engineering of support of deep foundation pit in Jinmin east street station on Suzhou Metro Line 2. Then, using PLAXIS finite element program, displacement field, internal force have been calculated in the progress of excavation of the practical engineering. The results calculated by F-SPW and PLAXIS have been compared simultaneously, the deformation of the support structure and its effect on the foundation pit have been emphasized in the thesis, from which some significative orderliness have been elicited. The main jobs and conclusions include:1. The design theory of pit-retaining structure has been studied by the numbers. The soil pressure theory actuality and the application and development of the finite element in the foundation pit have been analyzed. At the same time, the mechanics properties of the deep foundation pit and the calculation theory of soil pressure and water pressure,have been researched.2. Initial stresses and displacements before excavation are investigated by finite element method and a new idea is proposed for formation and calculation of excavation release load through expatiating the finite element theories and methods during the processing of deep foundation excavations.3. PLAXIS, an huge geotechnical engineering finite element program, has been introduced. In accordance with engineering of support of deep foundation pit in Jinmin east street station on Suzhou Metro Line 2, general analyses and researches on the processing of deep foundation excavations have been done according to a plane model established by PLAXIS. The displacement, plastic field and the settlement of surrounding foundation pit have been calculated during different excavation steps, and compare the results above with the design software 'F-SPW', which validates the correctness of the new-built model and the properness of adopted parameters.4. Combined with practical measurement of engineering, factors of design,construction and natural environment on effect of deformation of retaining structure are studied by PLAXIS finite element program. These factors include excavation depth of foundation pit, rigidity of timbering structures, action of the brace, reinforcing of soils, the order of excavation and deformation modulus of soil mass etc.The important factors are analyzed by quantification, and deformation of timbering structures in foundation pit excavation and the developing and changing rules of the settlement of surrounding stratum have been founded out. Some measurements, which offer reference to design and construction of deep foundation pit, to control deformation of foundation pit have been forward.