الفهرس 
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Abstract
In this thesis, two study cases were performed to study the tunnel-soil system
under static and seismic loads and also to verify the constructed model by
Plaxis. The first case study was performed on the tunnel soil system
considering continuous tunnel lining. In the verification study, soil was
modeled using Mohr-Coulomb equivalent linear elastoplastic model to
compare results with the nonlinear soil model used by Abdel-Motaal et al.
(2014). Results are also compared with results calculated by analytical
expressions using Penzien & Wu equations (1998). Construction stages were
taken into consideration in this case.
The second case study was performed on a Contract BC-24 Phase II Delhi
Metro Line, which consists of a segmental tunnel with five segments and a
keystone to study the effect of seismic load on the tunnel. Joints were
modeled using hinges with free rotations. Construction stages were ignored
in this case. Results were compared to results by Chow et al. (2008).
In the two cases, the tunnel soil system was modeled using a 2D Plane strain
model using Plaxis 2D program. Mohr-Coulomb’s model was used to
simulate soil behavior. Soil elements modeled using 15 nodes triangle
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elements. Tunnel lining was modeled with plate elements using a linear
elastic model to simulate concrete properties. The earthquake was applied at
the bedrock surface.
Initial parametric study using seven different earthquakes was carried out on
continuous tunnel lining. Study focused on the difference in internal forces
in tunnel lining and displacement in tunnel lining under the effect of these
earthquakes.
As a main stage, a parametric study on segmental tunnel lining using a
selected earthquake ground motion was performed by changing earthquake
intensity, lining thickness, tunnel diameter, tunnel depth and the number of
tunnel lining joints. The main aim of this study is to investigate the effect of
these factors on the internal forces and settlement trough.
6.2 Conclusions
The research findings are summarized as follows:
1) Two-dimensional finite element modeling (2D FEM) using the Plaxis
program can accurately describe the behavior of the tunnel soil system
under static and seismic loads.
2) Applying the equivalent soil method using the Mohr-Coulomb model
provides acceptable results compared to the results of the nonlinear
model.
3) Construction stages for constructing tunnels using TBM must be taken
into consideration to get true values for straining actions in tunnel
lining under static loads.
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4) Changing the absolute peak acceleration at the base affects the shape
of the acceleration time histories.
5) Peak values of acceleration at the ground surface increase with
increasing peak values at the bedrock surface.
6) The peak values of acceleration are magnified at shallower depths
above the bedrock towards the ground surface.
7) Increasing intensity of earthquake causes an increase in bending
moment, normal force and displacement of tunnel, for the same
earthquake.
8) For the same base acceleration, there is a variation in values of
bending moment and normal force for the different earthquakes.
Consequently, for tunnel design, it is recommended to consider
different earthquakes.
9) Increasing the lining thickness is associated with a considerable
increase in the maximum bending moment. It can be clarified as
increasing lining thickness leads to an increase in its rigidity and hence
the developed bending moment.
10) The max. normal force in the tunnel increases with increasing
earthquake intensity.
11) For small earthquake intensity (0.05g) increasing tunnel rigidity by
increasing the t/D ratio does not affect max normal force value.
However, for higher intensity, increasing rigidity ratio from 0.0375 to
0.0625 leads to a decrease in normal force with an average percent
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equal to 16%, however, changing rigidity from 0.0625 to 0.1125 has
a limited decrease in values of normal force with an average equal to
5%.
12) In general, increasing tunnel diameter leads to a great increase in the
max bending moment in tunnel lining. The average percent of the
increase in bending moment by increasing diameter from 6m to 12 m
is 260%.
13) For the different lining thicknesses, increasing tunnel diameter leads
to an increase in the maximum normal force. from diameter 6m to
12m, the average increase in normal force is 400% for the different
thicknesses.
14) As a result of increasing the number of tunnel lining joints, the max
bending moment in the tunnel lining decreases with great values. For
example, the average percentage of decrease in bending moment, by
using six tunnel joints is 44% compared to the continuous tunnel.
15) For low rigidity tunnel, the existence of joints has a low effect on
bending moment values compared to high rigidity tunnel.
16) The number of tunnel lining joints has a considerable effect on the
developed bending moment for a low number of joints (less than 6
joints). After that, increasing the joints number have a relatively less
effect on reducing the developed bending moment.
17) Increasing the number of lining joints is associated with a considerable
decrease in the values of the developed normal force.
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18) For small lining thickness (t=0.3m, t/D=0.0375), the reduction
percentage in normal force is limited as the tunnel is flexible enough
to be affected by the number of joints. Contrary, in rigid tunnels such
as the case of (t=0.9, t/D= 0.0875) the reduction percentage in normal
force is 54% in the case of using 12 joints.
19) Changing tunnel depth has a low effect on max. bending moment
values thus for high earthquake intensity, average percentage of the
increase in bending moment is about 25%. However, for low
earthquake intensity, average percentage of the increase in bending
moment is about 85%.
20) Increasing tunnel depth is associated with a considerable increase in
values of normal forces as a direct effect of increasing the overburden
pressure.
21) In general, seismic excitation is associated with high considerable
values of surface settlement, relative to the static loading condition.
22) Increasing the number of joints is associated with a considerable
increase in the surface settlement (more than 30 % increase). These
predicted changes are due to increasing the tunnel lining flexibility by
increasing the total number of joints.
23) Increasing tunnel diameter leads to increase values of settlement under
seismic load. The increase extends for long distances from the
centerline. Similar to the previous, this observation is due to
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increasing tunnel flexibility by increasing tunnel diameter or the total
number of joints.
24) The effect of decreasing the ratio of lining thickness to tunnel diameter
makes the tunnel more flexible and as a result settlement values
increase. This notice is observed locally just above the tunnel location
(about 10%) and vanishes gradually in the lateral direction.
6.3 Recommendations for future studies
1) Increasing the range of the studied parameters such as the distribution
of joints, and height of the surrounding soil layer.
2) Study segmental tunnel soil system for different types of soil.
3) Study the effect of the existing groundwater table at a certain depth.
4) Studying the axial forces and moments in the longitudinal direction of
the tunnel and their variation during the earthquake, also study the
effect of longitudinal joints.