With more than 14 million residents Istanbul is one of the largest cities worldwide, the only one spanning the two continents: Asia and Europe, and bordering the Black Sea and the Mediterranean Sea. For that reason, it´s not surprising that a megacity like the Turkish Metropolitan area is in need of many tunnel solutions. Especially in the field of infrastructure the government is investing huge sums to improve fresh- and wastewater management, traffic and public transport.

According to European Union reports, Turkey is one of the fastest growing markets for wastewater solutions. The Turkish Wastewater Treatment Action Plan 2023 provides that the number of treatment plants will increase from around 650 in 2015 to more than 2150 in 2023. The expansion and conjunction of the existing wastewater tunnel system is arguably one of the most important topics officials are facing. One of these projects is the bypass tunnel for the wastewater line in Istanbul’s Zeytinburnu district.

The Zeytinburnu tunnel

The 3.91m-diameter EPBM from Lovsuns/LNSS finished its exacavation some months ago–the first 2km-long bypass in Zeytinburnu to discharge the existing system. The aim of the Ayvali-2 Tunnel is to increase drainage wastewater capacity of the existing lines of Bagcilar, Esenler, Gungoren and Zeytinburnu. The Tunnel will carry the wastewater of these main hubs of Istanbul to the Yeni Water Treatment Facility.

First breakthrough in September 2016

The Turkish construction company Eferay Yapi Ticaret together with the Canadian-Chinese Lovsuns Tunneling Canada celebrated the first breakthrough of the 3.91m-diameter single shield EPBM in September 2016. The TBM launched from a 21m-deep shaft and broke through into a 12m-deep target shaft after around nine months boring. Normally the drive could be expected to be much shorter, but due to problems with muck transportation during the winter, processing on the job site took more time than expected. The TBM for the wastewater tunnel was one of the first contracts for the Lovsuns Company (formerly Lovat and now an overseas subsidiary company of Liaoning Censcience Industry [LNSS]).

Project manager Muammer Cinar explains the situation for the TBM works: “The overall project includes 10km of tunnels, divided into an initial 2km and a second 8km section. After one month of assembly, the TBM started to drill the first section in the middle of December 2015.“


The geology found in the area showed sandstone, siltstone, clay and soil with high groundwater inflows. During the last 150m drive, the TBM headed under a highly-populated area. Here grouting to stabilise the ground helped to prevent higher water ingress and simultaneously secured the stability of the buildings on the surface. Due to these measurements the advance of the tunnel was very good. Thanks to the crew and the machine the best shift showed an advance of 15.6m, the best daily advance was 31.2m and in the best week 153m of the tunnel was driven. The best monthly advance occured in April 2016 with 512m. The usual overburden was between 8m and 40m, however in the last 150m before reaching the target shaft, the tunnel passed just 6m below the foundations of the nearby housing areas.

After the first breakthrough in Zeytinburnu, the TBM was disassembled and transported to the second launch shaft in Ayazaga, also situated on the European Side of Istanbul. The second drive will be 7.29km long. It is also a discharge tunnel, between the existing wastewater tunnels of Kemerburgaz and Ambarli. Here the ground will be limestone and sandstone. The drive will be divided into two sections with an intermediate shaft after 4km. All shafts have a diameter of 9m. Originally it was planned to use more shafts, but due to the small diameter of the TBM this was not necessary. The drive is expected to start early this year. The inner lining will be constructed with concrete 5+1 segments, which are built in a segment factory 20 to 25km away and delivered to the job site as needed.

Muck removal

For muck transport a locomotive is used in the tunnels. The muck is then transported by trucks to an old mining area in the northern part of Istanbul. This is the only place to deliver the muck for the whole European Side of Istanbul and especially in winter it is very difficult for transportation.

TBM data

The TBM is an EPB designed as a mixed face (soft ground and rock) single shield. The shield diameter is 3.91m with a cutting diameter of 3.94m. The maximum pressure is 3 bar. The machine is designed for a minimum curvature radius of 400m and a maximum advance rate of 6m/h. The whole TBM is 89m-long with a shield length of 8m and a back-up length of 80m, altogether approximately 650t heavy.

The shield is equipped with 20 single, two twin and one quad replacable disc cutters for the rock cutting mode and 28 ripper teeth, 40 scraper tools and two oil pressurized wear indicator ripper teeths for the soft ground configuration. The hydraulic main drive contains motors that deliver a total power of 524kW to the cutting head. Maximum torque of the cutting head is 1,883kNm with a speed of 2.66 rpm. The operator station is specially equipped with a programmable logic controller (PLC), which controlls all machine functions and records the data. Integrated in the PLC is a logging system recording information about the performance of cutterhead, screw conveyor, main drive, grout injection and other systems.

Additionally the TBM has an automatic guidance system and ground conditioning System with a foam injection rate of 60 m3/h (1,000 l/min). The grout injection system delivers two different components (component A with 12 m3/h and component B with 1.2m3/h) with 16 bar maximum pressure. The ventilation system has a capacity of 150m3/min. A refurbished machine for the Istanbul metro

In 2017, and solely for the extension of the metro system a total of 24 TBMs will be ordered for job sites in Istanbul. For the extension of the Metro Line M7 Lovsuns delivered a CAT 6.12m EPB that was previously used in the Toronto Metro Project in 2010, refurbished in Toronto and skinned up to 6.5m. The TBM started the 4km drive end of 2016 in the highly populated Kabatas area on the European side of Istanbul to bore two sections.

The daily traffic in the metropalitan region of Istanbul is a huge problem. The Istanbul Metro began services in 1989 to redistribute the commuter traffic from the streets to underground transportation. Four Metro Lines on the European and, since 2016, two on the Asian side of Istanbul are used by more than one million commuters, with rising numbers. The Istanbul Metro system consists of nearly 90 stations (more than 65 underground) and is at the moment around 150km long.

Five more lines are planned to be built or have construction ongoing, which will almost double the number of stations and increase the coverage for Istanbul’s commuters:

¦ M3: Kirazli – Bakirköy-IDO (planned to open in 2019)

¦ M4: from Tavsantepe (formerly known as Kaynarca) to Istanbul-Sabiha Gökçen International Airport (7.4km; construction finish is planned for 2018)

¦ M7: Mecidiyeköy – Mahmutbey; construction began in Feb 2014 and was later extended from Mecidiyeköy via Fulya, Yildiz (old: Darphane on map) and Besiktas to Kabatas, totalling around 24.5km with 19 stations (due to open in 2018)

¦ M8: Cross-city Line on the Asian side from Bostanci to Dudullu (14.3km, start of operation is planned for 2019)

¦ M9: Tangential Line through western suburbs from Ikitelli Sanayi to Ataköy (13km, planned to be finished in 2019) All lines on the metro system are operated by Metro Istanbul.

Metro m7, fulya to Kabatas

As mentioned, the Istanbul Metro is currently undergoing a massive extension with more than 70 stations and more than 330km of route under construction. Most of this will be constructed on completely new lines and some will be added to the existing routes. The Metro M7 is the largest project, started in 2014, and is to be executed in two stages and is planned to start service in 2018. The new route includes 19 stations from Mahmutbey in the Northwest to Kabatas in the Southeast, an important ferry hub for commuters between Asia and Europe.

LogisticaL challenges

“The very narrow urban environment is challenging the job site for the tunnel works extremely”, explains tunnel manager Yigit Gencay from Alsim/Alarko. “We started to prepare the 81m-wide and 105m-long job site in January 2016 by securing the surrounding mountaineous residential zone with earth piling.”

Originally the Metro line should end in Mecidiyeköy, but then plans changed and the Metro was extended to Kabatas with four more stations. The original plan was to build only a launch shaft and a parking house in Fulya, but then changed to a Metro station due to the high population in this district. The civil works were given to two different contractors and Alarko won the contract for the extension line, the construction of the station and all electromechanical works. Two shafts are situated at the Fulya job site. One is the launch shaft for the TBM to drive to Kabatas with return in a second tube back to Fulya. The shaft is 33m deep with a 12m diameter. The 4.5km tunnel will go from Fulya via Yildiz and the very popular Besiktas area to the final station, Kabatas, directly at the ferry port. From the second shaft the tunnel heads in NATM to Mecidiyeköy.

Underground the two shafts at the Fulya job site will be connected to the Metro station platform, which will be 240m long underground, 80m long on the surface.

Using the launch shafts for the TBM and the NATM tunnels, the underground station was built first. Then, from the wall of the station in the direction of Kabatas, a 15m-long Pilot Tunnel was drilled and a thrust frame was built for the TBM. After that, the 110m-long TBM with back-up was assembled in the station to start drilling in the Pilot Tunnel in EPM mode as soon as possible. At Yildiz and Besiktas station, first of all, the stations will be built and then the TBM driven through the stations. Once it reaches the final station, Kabatas, the Lovsuns TBM will be disassembled and used for further projects of Alarko.

Ground conditions for EPB

“Our mixed TBM serves perfect the counter balance between ground conditions and ground water with the cutting shield”, explains Gencay. In the Fulya area there is only some ground water in sand- and mudstone expected. Towards Besiktas this includes Aluvium and Clay zones, further to Kabatas sea water may appear due to the very close Bosphorus. The TBM is designed to operate under 4 bars of pressure. The tunnel alignement is planned to be 33m deep in Fulya, 80m in Yildiz, 20m in Besiktas and finally 40m in Kabatas. The tunnel slope from Fulya to Kabatas is graded 4.5 per cent downwards.

Especially in the Besiktas and Kabatas areas a water pressure of 2.5 bar with very fast changing ground conditions are expected. For the client and the contractor design and TBM choice was very important—that they have a lot of different options to react on the different ground conditions. For that reason the TBM is capable to use polymer pumping equipment and also pressurised bentonite in the cutting chamber with additives, foam and air. If there is a loss of pressure caused by critical ground conditions two pressurised and one electronical bentonite tank can be used to stabilise the ground.

To fill the gap between the ground and the outside of the lining, grouting is supposed to be done as quickly as possible. The TBM shows a two component grouting system: 1) a grout mixture made of cement, bentonite, water, a filler like fly ash, retarder or stabiliser (24-hour reaction time) and 2) a sodium silicate (accelerator for grouting), which speeds the stabilising of the grout mixture as quickly as possible To prevent settlements due to the difficult ground conditions and to protect the historical as well as the residential buildings, drilling and installing the segments must be done more or less simultaneously. But with the grout mixture, which needs 10 to 15 seconds of gel time to become stable, it is much easier.

The grouting pressure will be 0.2 bar more than the ground pressure. To inject the grout there are eight grout lines in total, but only four lines will be used at the same time. To make sure that the working area is safe, at the outer ring are three brushes installed containing greas.

The TBM is also designed to carry out probe drilling. On one hand it is possible to know more about the ground in front of the shield, but on the other, if the ground is collapsing or very fractured, it is easier to arrange an umbrella shield with 12 angled boreholes.

The contractor also tried to stay on the safe side by ordering a TBM that is built with a very durable steel quality. It may require longer stops due to repair works in the cutting chamber. Another important feature for the contractor was the double articulated shield.

Refuge chamber

A refuge chamber has been included to secure 10 persons for 24 hours in case of a disaster. Altogether 25 people work in one shift in- and outside the tunnel (13 to 15 people in the tunnel). The weekly personal plan is to work in two shifts each 10 hours for six days the first and seven days the second week.


The logistical problems for a job site in this overcrowded, highly-populated city are huge. Everything needs to be delivered on time or directly transported to an outside storage area. The logistic center on the Fulya job site is very small. The muck will be transported in the tunnel with rolling stock and muck cars to the shaft, taken with a crane from shaft ground to surface and dumped in a 20.5m-long, 35m-wide and 4m-high pool and also continously cleared.

Transportation by truck is not easy and needs to be adjusted without break. Every day aorund 60 dumpers with 40t loading capacity leave the job site in direction to the dumping station around 25km away.

The segments – enough to build 15 to 20 rings every day – reach the job site from the segmental production plant which is 25km away, and also just in time due to a very limited storage capacity.

Construction Progress

The in the middle of September 2016 assembley of the TBM started and in mid October 2016 the first ring was built. The total construction time for the tunnel with the Lovsuns EPB TBM only in the direction from Fulya to Kabatas is planned with 12 to 13 months. After the start of railworks,

electromechanical and signalling works, the interior construction of the station will be executed.

The distance between both tubes is around 32m and becomes closer as closer the tunnels reach the station.

The second tube from Kabatas to Fulya starts around six months later due to archeological examinations in the Kabatas and Besiktas area