A thesis submitted in partial fulfillment of requirements for the degree of Master of Engineering in Geotechnical and Geoenv ironmental Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 2007

This study deals with the evaluation of measured longitudinal surface settlements obtained from the Blue Line subway project and the corresponding 3D numerical simulation. The simplified numerical procedure, proposed by Mroueh and Shahrour (2008), is adapted with two main parameters: the partial stress release factor Üdec and the length of unlined zone Ldee. The effects of these parameters on the surface settlement are investigated. From the evaluation of 11 measured points, the surface settlements mainly occurred between 4D ~ -4D and a large portion of ground surface settlements occurred after the shield passing: 19 ~ 49 % of total settlements occurred at the tunnel face, 7 ~ 23 % in the unlined zone and 34 ~ 71 % due to complete release confinement (1- Üdec). The maximum surface settlement varies from 16 mm to 34 mm. The numerical results show that the ground surface settlements mainly occurred 2D ~ -4D. A large portion of ground surface settlement occurred after the shield passing: in the unlined zone and complete release confinement (70 ~ 75 %). The numerical simulation highly depends on the values of Üdec. The measured surface settlement can be predicted within the range of Üdec= 0.2 ~ 0.7. The changing of parameter Ldec, related to the length of unlined zone, does not seem to take much effect on the magnitude of total settlement