| Towheed Tunnel Construction Project
Towheed Tunnel Project is an urban underground structure, located within the area of Chamran Highway, Towheed Square, Jomhouri Square, and Navab Highway, with a length of about 3 km (Tunnel + entry ramps).
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Subsequent to studied on the Comprehensive Plan of Tehran, in order to make an easy access from the north to the south of Tehran and vice versa, along the north-south corridor, between Chamran Highway constructed during the 70s, and Navab Highway constructed during the 90s, sufficient studies were made by Tehran Municipality in 1998 so that the connection of the said two Highways, i.e. to fill the gap between Towheed Square to Jomhouri Square becomes practicable and operational.
The significance of the above issue, the congested traffic on Tehran highways, and the intense exigency of Tehran as a metropolitan city to have the above Highways connected, made Tehran Municipality to launch exhaustive studies to tackle such purpose, and by comparing the existing alternatives, the best alternative which was construction of a tunnel similar to Tehran Ressalat Short Tunnel, was adopted and approved.
To this end, in early 2007, a Contractor (Perlite) was assigned to construct the Project, and on 11.06.2007 the contract to kick off the Project was signed and notified to the Contractor, whereby on 19.06.2007 the construction works of Towheed Tunnel Project were actually commenced.
General Specifications
• Client: Engineering and Construction Division of Tehran Municipality
• Poject Manager: Operational Management of Engineering Structures Co. (Maram)
• EPC Contractor: Perlite Company, assigned with the above task in respect of its precedent successful quality achievement in the construction Tehran Ressalat Tunnel Project.
The construction site of this Project was located within the distance between Fatemi Ave. in the north of Towheed Square, and Navab Highway in the south of Azerbaijan street junction.
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Traffic Impacts
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Provide easy access for Tehrani
citizens to drive from Azadegan
Highway, Saveh-Qom Highway,
Hamedan-Esfahan Highway,
Behesht-e-Zahra Cemetery,
and Imam Khomeini International
Airport, towards the north part of
Tehran and vice-versa,
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A General View of Jomhouri Shaft |
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Maintain a continuous drive of vehicles with a certain speed of international standard along the said route,
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Reduce traffic on the axis of Chamran-Navab Highways, Azadi Ave., and the axes of Jomhouri Square and the neighborhood streets within the Project area,
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Decrease duration of intercity trips and the running traffic,
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Increase average permissible speed of the vehicles.
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Economic Impacts
- Reduce wear and tear rate of vehicles,
- Reduce cost of vehicles maintenance,
- Reduce rate of spare parts used by the vehicles
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Social Impacts
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Decrease pollution of environment
for millions of Tehrani citizens
resident in Tehran and its suburbs,
including such pollutions as air,
noise, psychological and neural
tensions arising from being delayed
by the congested traffic, which result
in substantial costs for the health,
medical treatment, death, reduce average rate of life expectancy, social problems of families, increase in social
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offenses, such as in number of clashes, quarrels, wandering children, youth dilemmas, and adverse effects on the community relationships.
- Change general vista of the city within the Project area, and subsequent increase in the number of local and international tourists for the improved urban facilities and aesthetics of the city.
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Technical Specifications of the Project
Towheed Tunnel Project was designed
in the shape of a twin tunnel adjacent
structure, shared by a middle interface
wall, and constructed by piles of 1.5 m
in diameter, spaced by a 4 m interval. |
Lining Work on the Crest of East and West Tunnels
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| The twin tunnels were excavated on a cross sectional area (face) of about 305 m2. |
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Each tunnel is comprised of three driving
bands, with a length of 2,136 m, and a
total Project length of about 3,000 m, of
which 864 m is for the ramps to enter and
exit the tunnels, and the total length of
the tunnels (for both entry and exit) is
4,272 m. |
Lining Work on the Invert of Towheed Tunnel
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about 12.5 m, which is contemplated for three pedestrian passages and two adjacent passages for the utilities service personnel to operate and maintain the Tunnel. The peak height of the tunnels is about 8.5 m, and the general height and width of the Tunnel for the passage of the vehicles was designed at 5 m and 11 m respectively.
The overburden soil on the Tunnel was minimum 6 m at the portals, but reached maximum 23 m at the I2 Subway station, and 21 m at Azerbaijan street.
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Construction Works Details
Given the tight limited time of the Project,
not only the Project was constructed both
from the north and south ends, but also
4 access shafts were contemplated along
the Tunnel length, i.e. at Towheed
Square, Niyayesh junction, Azadi junction,
and Jomhouri Square.
Meanwhile, the shaft sunk at Niyayesh
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Additional Excavation Work on the South Ramp
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Street will be used as a ventilating shaft to ventilate the Tunnel in future.
Given 29 months to complete such a burdensome massive project, accompanied by a difficult and complicated location to handle and heavily congested traffic, makes construction of such Project an unprecedented unique record in the world, which is also considered as one of the greatest honors for the Iranian Engineering Society.
Some Unique Features of Towheed Tunnel |
Some unique and outstanding features of
this Project in Iran and even in the middle
east, is the passage of the Tunnel route
underneath Tehran Subway lines 2 & 4
which construction operation was
proceeded in light of the domestic experts’
technical knowhow and engineering,
accompanied by the efforts exerted by the
site personnel in this critical risky area.
Towheed Tunnel Project passes
underneath Tehran Subway at two points.
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Installation of Drainage Channels in the mid Tunnel Invert |
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The first point is where Line IV of Tehran Subway which is under construction and is located beneath Azadi Avenue and the second point is where the Tunnel route passes underneath Tehran Subway Line I-2 which is under operation. |
Given that Subway tunnel for line IV
was under construction, after necessary
coordination made between Subway and
Towheed projects, and providing certain
measures by Perlite experts, Towheed
Tunnel smoothly passed underneath Subway
line IV. |
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However, the passage underneath Subway
station I-2 was a rather different and complicated issue. As it is shown by the longitudinal section of the Tunnel, the point I-2 is considered the deepest point of Towheed Tunnel Project, and the Tunnel crest with a span of about 305 m2, which is deemed a big cavern, passes underneath the foundation of Subway I-2 station by a tight spacing of under 1 m (i.e. about 80 cm). It is noted that by a special highly |
technical
and precision design, the Tunnel could
pass underneath the Subway line by a
tight spacing.
Towheed Tunnel Longitudinal Section
Slope of northern ramp: 6%
Slope of southern ramp: 4.29%
Average slope of Tunnel: 4%
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The width of the station area was about 40
m2, within where by making necessary
changes in the work procedure, revocation of
heavy excavation machinery, changes in
the properties of temporary protection
frames, deployment of highest coefficients
in design and safety, and highly precise
control of construction works, Towheed
Tunnel was ultimately able to get through
underneath the Subway station, without making an instant
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Longitudinal Profile of Towheed
Tunnel making an instant |
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delay to the normal operation of the Subway station in progress just above. |
By the installation of instruments on the structure of
Subway station roof, including numerous surface
settlement gauges (to monitor settlement by a
precision of 0.01 mm), tilt meters (to monitor tilting
of the Subway station by a precision measurement of
angle at 0.01 sec), and various convergence gauges
during excavation of the Tunnel; the operations were
achieved without any report of outside permissible
limits settlement. In order to place concrete of
Tunnel crest underneath Subway station I-2, special
formworks were ordered to German Company Peri,
which were 3 m in length, with special feature s, and
the concrete was placed along the Tunnel with the least excavation under the roof.
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Passing underneath Tehran Subway Station I2 by special measures. |
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Construction of Semi-Tunnels
As to Ressalat Tunnel and most of the existing tunnels,
the flow of the traffic enters the tunnel without any
interval between the outside and inside the tunnel
(as portals of most tunnels are vertical). In the instant
entry of the traffic flow into the tunnel (or coming out of
the tunnel), due to a sudden change in the intensity of the light,
the eye is unable to adapt itself to such change
of light; and although in the modern tunnel projects, a
cascade of light is provided at the entry to and exit from the tunnel to increase the |
A view of elevators to haul earth in Azadi workshop |
illumination at the
immediate space to and fro the tunnel to
facilitate the eye’s adaptation to such change
of light intensity, but such arrangement
requires extra costs for considerable
number of lights to be installed and
consumption of electricity. |
Lining work on the roof of semi-tunnel in north ramp |
But, in the case of Towheed Tunnel, by
design of semi-tunnel structures at both
portals of Tunnel entry and exit, 50% of
the Tunnel roof is retained, and such roof
semi-console is gradually reduced along the
entry and exit ramp walls of the Tunnel,
and it is gradually transformed into a
vertical position. Such feature not only
adds to the aesthetics of the Project, but
also it provides a shady dim space for the
traffic at the immediate entry to or exit
from the Tunnel, thereby partially offsets a |
A view of semi-tunnel wall in the south ramp |
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part of required energy for providing the light cascade, and provides for adaptation of the eye to the sudden change of light intensity when the vehicle first passes through the shady space and then enters the Tunnel space, or during coming out of the Tunnel, a vehicle first leaves the dark space, then enters the shady space of the semi-tunnel, and finally enters the intensely luminous space outside, which saves considerable energy to be used to supply the light cascade.
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In addition to the above advantages, the
semi-tunnels are used as U-Turns, and by
contemplating a route on the upper level of
the Tunnel, Chamran Highway will be able to
shift the route of the traffic outside the
Tunnel. Such features of the Tunnel together
with the attractive view of the precast
concrete segments and the red brickwork
and the precast concrete light bases, will
constitute a valuable memorial devised by the
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Lining work on the roof of semi-tunnel in the north ramp |
Engineering Society of Tehran. Among
other significant features of this Project
are the technical and empirical abilities of
3,400 construction manpower, including
200 engineers and surveyors working three
shifts, and using 708 Nos. of modern light
and heavy equipment, all designated to the
construction of the Project. |
East and west semi-tunnel works in the north ramp |
| Meanwhile, compared with other tunnel projects, even Ressalat Tunnel, the most advantageous privilege of this Project is the speed of construction work progress which is about 10 times higher |
The equipment used in Towheed Tunnel
is of the best hi-tech and engineering
equipment, among others, 70 jet fans and
12 axial fans to ventilate the Tunnel by
driving out the exhaust air, and letting in
the fresh air, and special and standby
generators anticipated so that if there is a
power cut in Tehran Grid Power, those
generators will automatically generate the
power to compensate the required power of
the Tunnel. |
Installation of utilities support in the tunnels |
Another great national prestigious honor for
the country and for Tehran Municipality,
especially for the contemporary mayor
of Tehran, is that the Project was
independent of any services by the foreign
experts, i.e. 100% of the personnel
involved in the Project were of domestic
manpower, and the most updated know-how
was employed. |
Formwork and concrete works of mid columns |
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Among other prominent features of this Project are proper management, regular weekly supervision and inspections made by the esteemed mayor of Tehran to the construction works of Towheed Tunnel Project, which was considered an important factor to enliven the activities proceeding round the clock.
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Some of the advantages of this Project a
re: supply standard illumination, provide
smooth light within the immediate area of
the portals, artificial illumination inside
the Tunnel (to avoid high intensity
dazzling lighting), install sewage system,
erect 2,500 piles and about 30,000
concrete segments, install a smart system,
and precise calculation and strengthening
measures of the Tunnel against earthquake
and destructive vibrations of the faults. |
Rebar and concrete works in the mid tunnel invert |
Utilities of Towheed Tunnel
It includes installation of utilities equipment in the Tunnel, and manufacture and mobilization of north and south fans combined ventilation equipment, and control building and Niyayesh shaft.
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70 jet fans, each powered at 30 KW.
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North fan combined ventilation equipment: 3 axial fans, powered at 600 KW.
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Niyayesh fan combined ventilation equipment: 2 axial fans (to let in fresh air into Tunnel) powered at 410 KW.
4 axial fans (to let out exhaust air from Tunnel) powered at 500 KW.
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South portal fan combined ventilation equipment: 3 axial fans powered at 990 KW.
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Air washing system at the air entering Niyayesh fans.
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Total number of lights in the Tunnel: 1,064 lights powered at 550 KW.
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Length of cables for the utilities: 220 km.
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Special and standby power generators (in case of a power cut in Tehran Power Grid, the lighting system of the Tunnel fed by these generators will be automatically switched on and the power will be compensated).
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Smart firefighting system.
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Traffic alarms.
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Intercom telephones.
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Closed-Circuit TV.
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Vehicles counter.
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Road closing system.
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Traffic signs.
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Thermal sensors.
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Air pollution sensors and other facilities.
Tunnel Drainage System
Towheed drainage system operates by various channels. The surface water accumulated around and the Tunnel will be drained into the canals installed along the Tunnel wall, and will enter into a channel which is installed exactly in the middle of both twin tunnels. The drained water will be conveyed through the latter channel to the south part of the Tunnel, and it will be carried away from the Tunnel by some kanats.
Major Work Item Quantities of Towheed Tunnel
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Excavation: 720,000 m3
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Length of Piling: 26,000 m
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Formwork: 56,000 m3
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Rebar: 28,000 tons
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Strengthened Structure and Framing: 15,000 tons
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Concrete Placement: 230,000 m3
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Shotcrete: 450,000 m3
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Mesh: 250,000 m3
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Concrete Precast Segments: 60,000 m3
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