الفهرس 
ACKNOWLEDGEMENTSOnly 14 pages are availabe for public view
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Abstract
Accurate reviewing the results we concluded that;
[1] All the programs yielded the same dimensions for the optimal model of
the tunnel. Comparison between single and twin tunnel system, a higher
stress was obtained in the lining of bottom twin tunnel compared with
the stress in single tunnel lining. It was found that, stresses in bottom
twin tunnel increased about 100% than stresses in a single tunnel.
Moreover, when trains pass through a tunnel, stresses decrease about 10%
for single tunnel and about 5% for twin tunnels.Also, in case of the twin
tunnel, construction of the bottom tunnel before the top tunnel is
preferable to decrease the stresses in the top tunnel lining.
[2] For twin tunnel configuration, it was found that :
Maximum surface settlement decreases with increasing the distance
between tunnels for different tunnel alignment. The distance between
tunnels has a major effect on soil movement and internal forces in
tunnel lining when this distance less than 2.20D for horizontal
alignment, 1.80D for diagonal alignment and 1.25D for vertical
alignment.
A slight difference in lining internal forces for the construction
procedure of twin tunnels, when distance between tunnels more than
previous values . These findings are consistent with previous studies
those given in the literature, for example (Chehade and Shahrour,
2007) found that the proper clear distance between tunnels equal to
2.0D for horizontal alignment and take the clear distance between
tunnels equal to 1.0D for vertical alignment . Although the results of
this research agree with previous results, but the results on the distance
between two tunnels and the tunnel diameter is only applicable to the
given ground conditions, which may be not applicable to other regions
with different conditions, which is a limitation.
[3] For railway alignment, it was found that :
The development of rail levels is affected to a great extent by the change
in vertical distance between tunnels (S3). The vertical and horizontal
grades developed in the metro line depend on twin tunnels distance
(vertical and horizontal) and lengths between stations, especially for twin
tunnels which change from vertical to horizontal alignment. This means
twin tunnel configuration with railway alignment leads to an increase in
metro line safety.
According to the results that have been obtained, the proposed twin
tunnels by contractor have some problems, i) The proposed distances
between tunnels are not appropriate distances comparing with the
calculated . ii) Higher gradients up to 3.5% .
Higher stresses were generated in the rail head due to increasing of lateral
forces on the rails which placed at horizontal curves. This stresses occur
at head side 1 (inner Side) and head side 2 (outer side) in the rail head.
Increasing of these stresses than the allowable stresses causes side wear
of the rails.
According to obtained results, increasing the lateral force from 4.77t to
9.06t leads to the following: (I) Increase the normal stresses in the rail
head to 260%. II) Increase the normal stresses in the rail web to 207%.
III) Increase the shear stresses in the rail head to 309%. IV) Increase the
shear stresses in the rail web to 135%.
[4] For both tunnel systems, higher displacement occurs in tunnel lining
during the earthquake, the total displacement changes randomly during
seismic waves. the maximum change in line with internal forces (bending
moment, shear force and normal force) occurs at third time of earthquake
duration . Horizontal twin tunnels are the most affected by seismic action,
then diagonal twin tunnels and single tunnel. In addition, vertical twin
tunnels are less affected by the seismic action compared to the other
systems. The maximum change of internal forces during an earthquake
occurs in shear force, then bending moment. Moreover, the normal force
is less affected by seismic actions
[5] The economic evaluation of tunnel systems has been carried. Empirical
formulas were obtained to estimate an approximate cost of single and
twin tunnel projects. Twin tunnel configuration is widely used in many
countries in spite of the higher cost of the twin tunnel project compared to
the cost of single tunnel projects. Total cost of the twin tunnels increases
(30-80%) more the total cost of single tunnel. The total cost of tunnels
varies from project to another according to tunnel diameter, overburden
height, tunnel configuration, length of tunnel between stations,
construction quality, type of rolling stock, type of TBM,… etc.