Certain geometry (50m * 18m) of excavation section was determined so that the results from 3D FEM model and 2D FEM model were comparable. Parametric study was done in order to investigate how the domain and mesh set-up influence the results in 3D FEM model. The 3D FEM model adopted the model set-up tested and adjusted in 2D FEM model. The deflections of sheet pile walls in both 2D models were at similar level. The soil and building material parameters were first tested in 2D spring model and 2D FEM model. Instead, 2D models were made for comparison and verification purpose. Since the construction of Spaarndammertunnel starts after the completion of this graduation project, no field data was available for verification.

The research focus was to investigate the advantages and disadvantages of applying 3D FEM modelling for deep excavations. The data for soil investigation and preliminary design were provided by CRUX Engineering BV. The excavation plan, retaining structure and building material were developed from the preliminary design of this project. The soil data was compared with Amsterdam North-South metro line database as well. Cone penetration tests and boreholes were carried out along the tunnel location. Soil parameters used in models were derived from in situ soil investigation. This thesis only focused on the excavation part of the tunnel project. It is an independent research project based on the Spaarndammertunnel project in Amsterdam.

This thesis discusses the use of 3D finite element method (FEM) in deep excavations, especially the simulation of sequential excavation method in 3D FEM model. Following a brief outline of the new techniques, stability solutions are given for several practical problems, including foundations, anchors, slopes, excavations and tunnels.3D FEM analysis for sequential excavation A new development, which incorporates pore water pressures in finite-element limit analysis, is also described. The methods are very general, and can deal with heterogeneous soil profiles, anisotropic strength characteristics, fissured soils, discontinuities, complicated boundary conditions, and complex loading in both two and three dimensions. The bounding properties of the solutions are invaluable in practice, and enable accurate limit loads to be obtained through the use of an exact error estimate and automatic adaptive meshing procedures. These methods, known as finite-element limit analysis, do not require assumptions to be made about the mode of failure, and use only simple strength parameters that are familiar to geotechnical engineers. This paper describes recent advances in stability analysis that combine the limit theorems of classical plasticity with finite elements to give rigorous upper and lower bounds on the failure load.

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