2. The Eurasia tunnel, a highly anticipated civil engineering project for Turkey.
The Eurasia Tunnel, in Turkish, is an underwater road tunnel crossing
the Bosphorus strait.
The 5 km double-deck tunnel connects Kumkapi on the European
part and Kosuyolu on the Asian part of Istanbul.
It crosses the Bosphorus beneath the seabed at a maximum depth of -106 m.
The TBM section crossing the Bosphorus is 3.4 km (2.1 mi) long while
another 2.0 km (1.2 mi) is constructed by New Austrian Tunnelling
Method (NATM) and cut and cover method.
Environmental category: A
The tunnel is under a water pressure of 11 bars.
There are two seismic joints installed, 524m apart. These allow for tunnel
sections to move 50mm transversely and 75mm longitudinally in the event of
an earthquake.
3. LOCATION
The Eurasia Tunnel is a road tunnel in Istanbul, Turkey, crossing underneath the
Bosphorus strait.
4. PROJECT SEGMENTS
The project consists of three main segments:
European side
Construction of five U-turns as underpasses and seven pedestrian crossings as overpasses along Kennedy Street
that stretches between Kazlıçeşme and Sarayburn as a shoreline road beside the Sea of Marmara. Widening of
the entire Segment 1, which is approximately 5.4 km (3.4 mi), from 3x2 lanes to 2x4 lanes.
Bosporus crossing
Construction of a 5.4 km (3.4 mi), two-deck road tunnel with two lanes on each deck, a
toll plaza and an administrative building on the western end and ventilation shafts on
both ends of the tunnel.
Asian side
Widening from 2x3 and 2x4 lanes to 2x4 and 2x5 lanes along an approximately 3.8 km (2.4 mi)
stretch of the current D100 road that links at Göztepe to Ankara-İstanbul State Highway, and
construction of 2 bridge intersections, 1 overpass and 3 pedestrian bridges.
5. SCOPE
‘Deep water’ Geotechnical Site Investigation:
Shallow Water Geotechnical Site Investigation:
Standard and Advanced Laboratory Testing:
6. TUNNEL BORING MACHINE
A tunnel boring machine (TBM), also known as
a "mole", is a machine used to excavate tunnels
with a circular cross section through a variety of
soil and rock strata. They may also be used for
micro tunnelling. They can bore through
anything from hard rock to sand.
7. Features of the TBM
Diameter: 13.71 m
Number of rings used: 1,672
Number of segments: 15,084
Width of segments: 600 mm
Segment-ring arrangement: 8+1
Ring length: 2 m
TBM operating pressure: 11 bars
Daily advance speed (avg): 8-10 m
Total excavation volume: 1,893,000 m3
Total filling volume: 334,000 m3
Total amount of concrete used: 542,000 m3
Total weight of reinforcement used: 65,000 tons
Length of cut-cover tunnel structures: 800 m
Length of TBM tunnel: 3,340 m
Length of NATM tunnel: 1,890 m
8. New Austrian Tunnelling Method(NATM) or Sequential Excavation method (SEM)
• The New Austrian Tunnelling Method (NATM) is trenchless tunnelling method in which the rock and soil of the
bore, the supporting formations, are formed into a supporting structure for the tunnel as the excavation proceeds.
• Initial support is provided by standard means. This method provides an economic benefit due to the cost and
efficiency of the process.
There are seven features on which NATM is based on :
Mobilization of the strength of rock mass
Shot Crete protection
Measurements
Flexible support
Closing of invert
Contractual arrangements
Rock mass classification
9. Advantages
Flexible – Support provide as required by the ground conditions .
Safe – Able to deal with locally unexpected ground condition, minimizing claims.
Adaptable – Optimizing equipment and crews, allowing multiple heading operations concurrent.
Disadvantages
High level of coordination, cooperation and communication.
Lower production rates.
Advantage and Disadvantage of Austria Tunneling Method
10. Cut and Cover
In a cut and cover tunnel, the structure is built inside an excavation and covered over with
backfill material when construction of the structure is complete.
Cut and cover construction is used when the tunnel profile is shallow and the excavation from
the surface is possible, economical, and acceptable.
Cut and cover construction is used for underpasses, the approach sections to mined tunnels
and for tunnels in flat terrain or where it is advantageous to construct the tunnel at a shallow
depth.
For depths of 30 to 40 feet (about 10 m to 12 m), cut-and-cover is usually more
economical and more practical than mined or bored tunneling.
Two types of construction are employed to build cut and cover tunnels;
• Bottom-up
• Top-down.
11. Bottom-up method:
The main site is excavated, with ground support as necessary, and the tunnel is constructed within. The tunnel may be
of in situ concrete, precast concrete, precast arches , or corrugated steel arches. The trench is then carefully back-
filled above the tunnel roof and the surface is restored.
Conditions Favorable to Bottom-Up Construction:
No right-of way restrictions.
No requirement to limit sidewall deflections.
Advantages of bottom-up:
It is a conventional construction method well understood by contractors.
Waterproofing can be applied to the outside surface of the structure.
Disadvantages of bottom-up:
Somewhat larger footprint required for construction than for top-down construction.
The ground surface can not be restored to its final condition until construction is complete.
13. Top-down method:
Here side support walls and cap beams are constructed from ground level typically with slurry walls . Then a
shallow excavation. Then a shallow excavation allows making the tunnel roof of precast beams or in situ concrete.
The surface is then restored except for access openings.
Conditions Favorable to Top-Down Construction:
Limited width of right-of-way.
Sidewall deflections must be limited to protect adjacent features.
Advantages of top-down:
Useful when great care is required due to existing services and utilities underground which cannot be moved or
removed.
Minimal disruption to above ground operations due to surface being reinstated before tunnel works are
complete.
Disadvantages of top-down:
Inability to install external waterproofing outside the tunnel walls.
More complicated connections for the roof, floor and base slabs.
16. REFERENCE
Stakeholder Engagement Plan for the Eurasia Tunnel Project Istanbul,
Turkey March 2011 ERM Group, Germany and UK ELC-Group, Istanbul
www.avrasyatunell.com
WWW.FUGRO.COM
