Analysis and Parametric Study of Deep Excavation With Diaphragm Wall Using Finite Element Based Software

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Addis Ababa University


Control of soil deformation is crucial for deep excavation in congested urban areas to minimize its effect on adjacent structures. Therefore, an analysis and parametric study is important to realistically represent the response of the soil to excavation and to predict the magnitude and pattern of ground movement. This thesis presents a study of the effects of deep excavations with tie back diaphragm wall in expansive clay and red silty clay which are located in Bole Medehanealem area and Arada respectively, and also in cohesionless granular sandy soil. The objectives of this study are to investigate the effect of different parameters on the prediction of ground movement by numerical analysis and to develop a method of estimating these effects quantitatively. Extensive review of relevant literature published in the past four decades was conducted in order to understand the trends and the key developments in this area. It was revealed from the literature review that the concurrent use of the observational method and the finite element method for monitoring and controlling of ground deformations around the excavation has become a norm for deep excavation projects. Parametric studies were carried out to identify important variables controlling the mechanisms of soil-structure interaction. The analyses focus on deep excavations supported by tie-backed diaphragm walls using techniques of top down construction. Exact site conditions and input parameters for the soil were incorporated as much as possible. The principal parameters considered in the study include soil type, depth of excavation, wall embedment depth, wall stiffness, and strut spacing. These variables were used to conduct a series of finite element analyses using simplified geometry and ground conditions for the purpose of achieving the objective of this thesis. Results of these analyses were recorded in terms horizontal displacement of the diaphragm wall, ground settlement behind the diaphragm wall, and bending moments induced in the diaphragm wall due to an adjacent deep excavation.



Element; Based ;Software