Deformation analysis of deep excavations in Shanghai soft soils
Yang, Zhenkun; Azzam, Rafig (Thesis advisor); Fuentes Gutierrez, Raul (Thesis advisor)
Aachen : RWTH Aachen University (2022, 2023)
Dissertation / PhD Thesis
Dissertation, RWTH Aachen University, 2022
The design of underground structures in urban areas is generally controlled by the need to limit construction-induced displacements. Excessive deformations may bring damages to adjacent infrastructures. The performance of deep excavations depends on a wide range of factors such as local geological conditions, construction methods, supporting types, and workmanship. Making reliable predictions of the performance of deep excavations is therefore challenging. Numerical methods have been widely used to solve deep excavation problems for the methods' capability to consider most critical factors in practice. Meanwhile, to calibrate the results from the numerical analyses, field measurements are needed.This research provides insights into the mechanisms of excavation-induced deformations through a series of three-dimensional finite element analyses and data analyses from field measurement. The main contents of this dissertation are summarized as followings:1.A series of parametric studies are carried out based on a simplified excavation to investigate the influence of the soil-wall interface properties and soil properties on the excavation-induced displacements.2.A more complex case history is studied through fully 3D FEM analysis to evaluate the capability of the numerical method in replicating the deformations of the deep excavation and the displacements of several adjacent infrastructures. The impacts of several essential factors are then explored. These factors include 1) joints between adjacent diaphragm wall panels; 2) appropriate way to consider the lower part of the diaphragm, which is for cutting off groundwater; 3) possible interaction with the elevated road, which is two times the excavation depth away from the excavation; (4) feasibility of two adjacent deep excavations carried out simultaneously. 3.Field instrumentation data from the case history of a project, in which monitoring data were recorded daily during the construction, are reported and analyzed. Compared with other case histories with similar conditions, several distinctly exceptional behaviors have been observed from the project. In addition, the impact of different construction procedures suggested by the monitored data are quantified using finite element analysis. Contributory factors for these behaviors are identified, and valuable lessons are learned from the case study. The relevant findings from this research should benefit both designers and contractors of deep excavations in soft soils.
- Division of Earth Sciences and Geography 
- Chair of Engineering Geology and Hydrogeology