3-D Analysing Theory And Its Application Of Deep Excavation Considering Effects Of Staged Excavation

With the development of the urban construction, more and more large scale and deep excavations appear. Some new techniques such as beam-slab composite bracing system and top-down method are applied. Horizontal elastic foundation beam method is the conventional method to analyze retaining structures, and is recommended by the corresponding national code. But the analyses based on elastic-spring model are always two-dimensional (2D), cannot consider the three-dimensional (3D) and staged excavation effects. For this reason, the theoretical solutions for those excavations that are complicatedly braced and staged constructed always differ from the field data. In this dissertation, on the basis of the studies so far available, 3D analyzing theory on deep excavation is studied in-depth. The main work is as follows.1. The current method for analyzing excavation is modified. Spatial beam elements and slab elements instead of planar truss element are adopted to model the retaining and strutting structure. Tangential soil springs are added on retaining piles. Incremental method is proposed to simulate the whole process of the construction. Sub-structure method is used to quicken the calculating speed. These improvements will facilitate the 3D analysis with FEM.2. A 3D FEM program is developed to analyze the retaining system in braced excavation, considering the staged excavation effects and the beam-slab composite struts. In order to improve the practicality and maneuverability of the program, the universal graphic interface (DXF) is used, which makes it easy to be interactive between this program and the existing CAD graphic program. The reliability of the program is validated by comparing the results of this program in a simple case with that of the existing commercial program (F-SPW).3. The effects of staged excavation, slab struts, non-uniform loads aroundexcavation are studied by 3D analysis on an idealized braced excavation. The results obtained from the numerical experiments are very useful for the optimal design of retaining structure and preparation of construction scheme in a deep excavation. Finally, the excavation of an actual case West Lake Cultural Plaza is simulated with the method and program developed in this dissertation. The spatial and time behaviors of the excavation are analyzed in detail. The similarities and differences between the theoretical results and the measured data are also discussed.