In heavily settled areas, deformations induced by the tunnel excavation may cause
serious damage to nearby structures. In this study it is aimed to model ground
deformations induced by main tunnels and connection tunnels excavations as well
as groundwater drainage. Therefore, it is necessary to study effective means of
controlling tunnel induced deformations. The main parameters affecting the
failure and deformation state of the soil around a circular underground opening
are the physical characteristics of the soil, the diameter of the opening, and the
support pressure. During the construction stage of Necatibey Station of KizilayÇ / ayyolu
metro line (Ankara, Turkey), challenging ground conditions involving
highly heterogeneous and locally water saturated foundation soils have been
encountered. Possibility of damage at the surface and/or on the underground
structures can be estimated using finite difference method (FDM) of analysis.
In this study, two geophysical methods namely Electrical Resistivity Imaging
(ERI) and Ground Penetrating Radar (GPR) were utilized to distinguish soil types
at the study area. By correlating these geophysical survey results with the boring
v
logs, 3-Dimensional soil profile was revealed at the study area to build up a basis
for numerical models.
3-Dimensional (3D) FDM analyses were conducted to assess tunneling induced
deformations, along with movements around shallow soft ground main tunnels
and connection tunnels. During sequential excavations, temporary and permanent
shotcrete lining was also simulated. The soil behavior is assumed to be governed
by an elastic-perfectly plastic constitutive relation based on the Mohr&ndash / Coulomb
criterion. The computed deformations around these openings have been compared
with the in-situ measurements. The results of the study revealed that the 3-D
elasto-plastic analyses yield comparably good correlation with the in-situ
measurements. Also, in this study, the effects of main tunnels excavations on each
other and the effects of connection tunnels excavations on main tunnels were
identified in terms of ground deformations. In order to simulate induced surface
settlement due to groundwater withdrawal at the site 3-D fully coupled (fluidmechanical)
numerical models were run using different time durations. The model
studies revealed that deformations monitored at the ground surface are directly
related with the tunnel construction practice. Pumping groundwater has very little
or no effect on the measured deformations.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12612539/index.pdf |
| Date | 01 October 2010 |
| Creators | Akturk, Ozgur |
| Contributors | Doyuran, Vedat |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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