Marmaray Technical Specifications

marmaray technical features
marmaray technical features

• There is a total length of 13.500 m, consisting of 27000 m, each of which is composed of double lines.

• Bosphorus crossing is made with immersed tunnel, line 1 immersed tunnel length is 1386.999 m, Line 2 Immersed tunnel length is 1385.673 m.

• The continuation of the immersed tunnel in Asia and Europe is provided by drilling tunnels. The length of the line 1 drilling tunnel is 10837 m, and the line 2 drilling tunnel length is 10816 m.

• The road is a ballast-free road inside the tunnels and is a classical ballast road outside the tunnel.

• The rails used were UIC 60 and mushroom hardened rails.

• Connection materials are HM type, which is elastic type.

• 18 m length rails are made into long welded rails.

• LVT blocks were used in the tunnel.

• Marmaray road maintenance is carried out with the latest system machines by our undertaking without interruption in accordance with the TCDD Road Maintenance manual and the maintenance procedures of the manufacturer companies prepared in accordance with EN and UIC norms.

• Visual inspection of the line is performed regularly every day, and ultrasonic inspections of the rails are performed every month with highly sensitive machines.

• Control and maintenance of tunnels are carried out in accordance with the same standards.

• Maintenance services are carried out with 1 Manager, 1 Maintenance and Repair Supervisor, 4 Engineer, 3 surveyor and 12 workers in the Road Maintenance and Repair Directorate of the Marmaray facility.


Superficial Metro Section Length 63 km
- Number of Stations on the Surface 37 Pieces
Total Length of Railway Strait Tube Crossing Section 13,6km
- Boring Tunnel Length 9,8 km
- Immersed Tube Tunnel Length 1,4km
- Open - Close Tunnel Length 2,4 km
- Number of Underground Stations 3
Station Length 225m (minimum)
Number of Passengers in One Direction 75.000 passenger / hour / one way
Maximum Slope 18
Maximum Speed 100 km / h
Commercial Speed 45 km / h
Number of Train Schedules 2-10 minutes
Number of Vehicles 440 (2015 year)


A Submerged Tunnel consists of several elements produced in a dry dock or a shipyard. These elements are then drawn to the site, immersed in a channel and connected to form the final state of the tunnel.

In the picture below, the element is transported to a sinking place by a catamaran docking barge. (Tama River Tunnel in Japan)

marmaray technical features
marmaray technical features

The above picture shows the outer steel tube envelopes produced in a shipyard. These tubes are then pulled like a ship and moved to a site where the concrete will be filled and completed (pictured above) [South Osaka Port in Japan (along rail and road) Tunnel] (Kobe Port Minatojima Tunnel in Japan).

marmaray technical features
marmaray technical features

Above; Kawasaki Harbor Tunnel in Japan. Right; South Osaka Harbor Tunnel in Japan. Both ends of the elements are temporarily closed by partition sets; thus, when water is released and the pool used for the construction of the elements is filled with water, these elements will be allowed to float in the water. (Photographs taken from a book published by the Association of Japanese Screening and Reclamation Engineers.)

The length of the immersed tunnel on the seabed of the Bosphorus is approximately 1.4 kilometers, including the connections between the immersed tunnel and the drill tunnels. The tunnel is a vital link at the two-line railway crossing under the Bosphorus; This tunnel is located between Eminönü district on the European side of Istanbul and Üsküdar district on the Asian side. Both railway lines extend within the same binocular tunnel elements and are separated from each other by a central separation wall.

Over the course of the twentieth century, more than one hundred tunnels were built for road or rail transport around the world. Immersed tunnels were built as floating structures and then submerged in a pre-screened canal and covered with a cover layer. These tunnels must have a sufficient level of effective weight to prevent them from floating again after installation.

Immersed tunnels are formed from a series of tunnel elements that are produced in prefabricated lengths of substantially controllable length; each of these elements is generally of the length 100 m, and at the end of the tube tunnel, these elements are connected under the water to form the final version of the tunnel. Each element is provided with a temporary set of insertion kits at the ends; these sets allow the elements to float when they are dry. The fabrication process is completed in a dry dock, or the elements are lowered to the sea as a vessel and then completed in a floating place near the final assembly.

The immersed tube elements produced and completed in a dry dock or at a shipyard are then drawn to the site; immersed in a channel and connected to form the final state of the tunnel. On the left: The element is pulled to a place where final assembly operations will be carried out for immersion in a busy port.

Tunnel elements can be pulled successfully over large distances. After the equipment operations in Tuzla, these elements were fixed to the cranes on specially constructed barges, which could enable the elements to be lowered into a duct prepared at the bottom of the sea. Then, these elements were immersed by giving the necessary weight for lowering and immersion.

marmaray technical features
marmaray technical features

Submerging an element is a time-consuming and critical activity. In the picture above, the element is shown to be immersed downwards. This element is controlled horizontally by anchoring and cable systems and the cranes on the sinking barges control the vertical position until the element is lowered and fully seated on the foundation. In the picture below, the position of the element can be monitored by the GPS during immersion. (Photographs taken from the book published by the Japanese Association of Screening and Breeding Engineers.)

marmaray technical features
marmaray technical features

The immersed elements are brought together and combined with the previous elements; After this process, the water in the connection between the connected elements was drained. As a result of the water discharge process, the water pressure at the other end of the element compresses the rubber seal, ensuring that the seal is waterproof. While the foundation under the elements was completed, temporary support elements were kept in their places. Then the canal was refilled and the required protection layer was added on it. After the tube tunnel finishing element is placed, the joints of the drilling tunnel and the tube tunnel are filled with filling materials that provide waterproofing. Drilling operations made with the Tunnel Boring Machines (TBMs) towards the immersed tunnels continued until the immersed tunnel was reached.

marmaray technical features
marmaray technical features

The top of the tunnel is covered with backfill to ensure stability and protection. All three illustrations show backfilling from a self-propelled double jaw barge using the tremi method. (Photographs taken from the book published by the Japanese Association of Screening and Breeding Engineers)

marmaray technical features
marmaray technical features

In the immersed tunnel under the strait, there is a single chamber with two chambers, each for one-way train navigation. The elements are completely embedded in the seabed so that after the construction works the seabed profile is the same as the seabed profile before the construction started.

marmaray technical features
marmaray technical features

One of the advantages of the immersed tube tunnel method is that the cross section of the tunnel can be adjusted in the most appropriate way within the specific needs of each tunnel. In this way, you can see the different cross sections used worldwide in the picture above. Immersed tunnels are constructed in the form of reinforced concrete elements, previously with or without dental steel envelopes and functioning with internal reinforced concrete elements. In contrast, in Japan since the nineties, innovative techniques have been used that use non-reinforced but ribbed concretes, which are prepared by making sandwiches between inner and outer steel envelopes; these concretes work structurally completely composites. This technique has been put into practice with the development of excellent quality fluid and compacted concrete. This method can eliminate the requirements for the processing and production of iron reinforcements and molds, and by providing adequate cathodic protection for steel envelopes in the long term, the collision problem can be eliminated.


Tunnels under Istanbul consist of a mixture of different methods.

marmaray technical features
marmaray technical features

The red section of the route consists of an immersed tunnel, the white sections are mostly built as a bored tunnel using tunnel boring machines (TBM), and the yellow sections are made using the cut-and-cover technique (C&C) and the New Austrian Tunnel Boring Method (NATM) or other traditional methods. . Tunnel Boring Machines (TBM) are shown with numbers 1,2,3,4, 5, XNUMX, XNUMX and XNUMX in the figure.

Drilling tunnels opened in the rock using tunnel boring machines (TBMs) are connected to the immersed tunnel. There is a tunnel in every direction and a railway line in each of these tunnels. Tunnels are designed with sufficient distance between them to prevent them from affecting each other significantly during the construction phase. In order to provide an opportunity to escape to the parallel tunnel in an emergency, short connection tunnels were built at frequent intervals.

Tunnels under the city are connected to each other every 200 meter; thus, it is provided that the service personnel can easily pass from one channel to another. In addition, in the event of an accident in any of the drilling tunnels, these connections will provide safe rescue routes and provide access for rescue personnel.

In tunneling machines (CPCs), the latest 20-30 is widely observed throughout the year. The illustrations show examples of such a modern machine. The diameter of the shield can exceed 15 meters with current techniques.

Operating methods of modern tunnel boring machines can be quite complicated. In the picture, a three-sided machine used in Japan is used, allowing an oval-shaped tunnel to be opened. This technique would be used where it was necessary to build station platforms, but it was not needed.

In places where the tunnel cross section changed, many specialized procedures and other methods were applied (New Austrian Tunnel Boring Method (NATM), drilling-blasting and gallery boring machine). Similar procedures were used during the excavation of Sirkeci Station, which was arranged in a large and deep gallery opened underground. Two separate stations were built underground using cut and cover techniques; These stations are located in Yenikapı and Üsküdar. Where cut and cover tunnels are used, these tunnels are constructed as a single box section where a central separating wall is used between the two lines.

In all tunnels and stations, water isolation and ventilation are installed to prevent leaks. For suburban railway stations, design principles similar to those used for underground metro stations will be used. The following pictures show a tunnel constructed by NATM method.

Where cross-linked sleeper lines or side joint lines are required, different tunneling methods are applied by combining. In this tunnel, TBM technique and NATM technique are used together.


Excavation vessels with grab buckets were used to perform some of the underwater excavation and dredging works for the tunnel channel.

Immersed Tube Tunnel was placed on the seabed of the Bosphorus. Therefore, a channel was opened on the sea floor large enough to accommodate the building elements; furthermore, this channel is constructed in such a way that a covering layer and protective layer can be placed on the Tunnel.

The underwater excavation and dredging works of this channel have been carried out from the surface down using heavy underwater excavation and dredging equipment. The amount of soft ground, sand, gravel, and rock expelled exceeded 1,000,000 m3 in total.

The deepest point of the entire route is located in the Bosphorus and has a depth of about 44 meters. Immersed Tube A protective layer of at least 2 meters is placed on the tunnel and the cross section of the tubes is approximately 9 meters. Thus, the working depth of the dredger was approximately 58 meters.

There were a limited number of different types of equipment that would allow this to be accomplished. Dredging Dredger and Tug Bucket Dredger were used for screening works.

The grabbing dredger is a very heavy vehicle placed on a barge. There are two or more buckets, as can be seen from the name of this vehicle. These buckets are scoops that are opened when the device is lowered down from the barge and suspended and suspended from the barge. Since the buckets are very heavy, they sink to the bottom of the sea. When the bucket is lifted upwards from the bottom of the sea, it closes automatically, so that the tools are moved to the surface and emptied on the barges by means of buckets.

The most powerful shovel dredgers have the capacity to dig around 25 m3 in a single working cycle. The use of grabbing combs is most useful in soft to medium hard materials and cannot be used on hard tools such as sandstone and rock. Grab dredges are one of the oldest types of dredgers; but they are still widely used worldwide for this type of underwater excavation and survey work.

If contaminated soil is to be scanned, some special rubber gaskets can be fitted to the buckets. These seals prevent the release of residual deposits and fine particles into the water column during the pulling of the bucket up from the bottom of the sea or ensure that the amount of particles released can be kept at very limited levels.

The advantage of the bucket is that it is very reliable and is capable of digging and dredging at high depths. The disadvantages are that the depth of excavation decreases dramatically as the depth increases, and that the current in the Bosphorus will affect accuracy and overall performance. In addition, excavation and screening cannot be performed on hard tools with ladles.

The Dredger Bucket Dredger is a special vessel mounted with an immersion type dredging and cutting device with a suction pipe. While the ship navigates along the route, the soil mixed with water is pumped from the bottom of the sea into the ship. It is necessary for the sediments to settle in the ship. In order to fill the vessel at maximum capacity, it must be ensured that a large amount of residual water can flow out of the vessel while the vessel is moving. When the ship is full, it goes to the waste disposal site and empties the waste; the ship is then ready for the next duty cycle.

The most powerful Traction Bucket Vessels are capable of picking up about 40,000 tonnes (about 17,000 m3) in a single working cycle and digging and scanning up to a depth of about 70 meters. Traction Bucket Vessels can dig and crawl in soft to medium hard materials.

Advantages of Pull Bucket Dredger; high capacity and mobile system does not rely on anchor systems. The disadvantages are; the lack of accuracy and the excavation and screening of these vessels in the areas close to the shore.

In the terminal connection joints of the immersed tunnel, some rocks were excavated and dredged near the shore. Two different ways have been followed for this process. One of these ways is to apply the standard method of underwater drilling and blasting; the other method is the use of a special chiselling device, which allows the rock to break apart without blasting. Both methods are slow and costly.

Günceleme: 26/03/2022 00:22

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