Analysis and Study on Flat Slab with Opening for Cover and Excavation Top-Down Method
|Keywords||Top-Down Construction Method (TDCM) Deep foundation pit FEM Flat slab with opening|
Top-down foundation pit bracing system is always designed according to the traditional method. As to the design of preformed hole is only considered from the perspective of actual construction, while the perspective of structural design by quantitative and the qualitative analysis is not considered. Characteristics of the top-down method and the main method of foundation pit bracing system are discussed. Considering the characteristics of construction by top-down method and the calculate method of foundation pit bracing system, method of considering the support structure and bracing system working together during the construction is proposed. As the soil has very strong nonlinearity, some improvements to the bar finite element method of elastic foundation are done, nonlinear analysis of foundation pit that assuming soil resistance and wall displacement to be hyperbolic is quoted to create the model. The numerical simulation of over all excavation has been realized successful by using the large-scale general finite element software ANSYS. Contrasting the textual calculation result with the measure of actual engineering, the result shows that the textual analysis method is viable, Finally,analysis and summarize the mechanics performance of floor for Cover and excavation Top-Down method and have found out some regular conclusions about the design of hole .The conclusion can be mainly summarized as follows: 1.Nearby unearthed mouth the suitable construction load could be advantageous to control the differential settlement. 2.The reservation hole should avoid to be opened in the middle of foundation pit; Some small unearthed mouth should be symmetrically constructed to replace large-scale unearthed mouth. 3.If the reservation hole of Supporting Structure is closer the pit outside edges,it will be more influential to side-sway and deformation of the Supporting Structure; If the lost floor is more near the middle of pit,it will be less influential to displacement and deformation of the Supporting Structure. 4.To prevent excessive side-sway and deformation, reserved holes should be avoided in the pit outside edge, especially in the Central of the outer fringes.