| Summary: | 碩士 === 國立中興大學 === 土木工程學系所 === 105 === Abstract
There are densely populated and land limited in Taiwan area. The land acquirement is getting more difficult with the rapid development of urbanization. More underground excavation engineering is widely carried out. The stability of retaining structure and the engineering properties of underground excavation in soft soil layers is worth studying further in order to provide the references of construction and design for relevant engineering agencies.
This study aims at the related mechanical behavior and engineering properties of underground excavation in soft soil layers with different excavated depth and groundwater level using Plaxis 2D finite element program. From the analyzed results, it indicates that: (1). the heaving quantity of final excavated surface is decreased with the groundwater level close to the surface compared with that in deep groundwater level because the effective unit soil weight is reduced. (2). under the condition of groundwater level close to the surface and 5.3m of excavated depth, the maximum horizontal displacement, moment and shear of retaining structure and axial force of horizontal support are increased in the rates of 72.7%, 24.2%, 48.5% and 50.2% respectively compared with those in deep groundwater level. (3). under the condition of groundwater level close to the surface and 9m of excavated depth, the maximum horizontal displacement, moment and shear of retaining structure and axial forces of upper, lower horizontal supports are increased in the rates of 0%, 130.6%, 41.3%、88.2% & 67.0% respectively compared with those in deep groundwater level. (4). There is little effect of horizontal displacement in the bottom of retaining structure for the location of groundwater level when the excavation is deeper in the soft soil layers and more soil mass is removed between the lower horizontal support and final excavated surface.
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