The Turkish construction company Eferay Yapi Ticaret A.S. together with the Canadian-Chinese Lovsuns Tunneling Canada Ltd. celebrated in Istanbul the breakthrough of the 3.91-m diameter single shield EPB TBM for a wastewater tunnel in September 2016. The project is an important step toward a cleaner environment for the metropolis of Istanbul.
Turkey is one of the fastest growing markets for wastewater solutions according to reports of the European Union. The Turkish Wastewater Treatment Action Plan 2023 provides that the number of treatment plants will increase from around 650 in 2015 to more than 2,150 in 2023. The Istanbul region with more than 16 million people is desperate for solutions and for that reason, every single meter of a wastewater tunnel is an important step for every citizen of Istanbul.
The 3.91-m diameter EPB tunnel boring machine from Lovsuns/LNSS is part of this visionary plan and finished the first 2-km long bypass in Zeytinburnu to discharge the existing system. The aim of the Ayvali-2 Tunnel is the increase of 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.
The TBM started in a 21-m deep launch shaft and broke through into the 12-m deep target shaft after around 9 months boring. Normally the boring time should be much more shorter, but due to problems with the muck transportation during the winter processing on the job site was longer than expected.
The TBM for the wastewater tunnel was one of the first contracts for the Lovsuns, formerly Lovat and now an overseas subsidiary company of China’s Liaoning Censcience Industry Co. Ltd. (LNSS). The TBM was designed by experienced ex-Lovat engineers and manufactured in the modern Chinese facilities of LNSS. After one month of assembly, the TBM started mining in mid December 2015.
The geology found in the area showed sandstone, siltstone, clay and soil below the groundwater table. During the last 150 m drive, grouting to stabilize the ground helped to prevent higher water ingresses and simultaneously secured the stability of the buildings on the surface.
Thanks to the crew and the machine the best shift showed an advance of 15.6 m, the best daily advance was 31.2 m and in the best week 153 m of the tunnel was driven. The best monthly result occurred in April 2016 with 512 m. The regular overburden was between 8 and 40 m, but the last 150 m before reaching the target shaft, the tunnel passed only 6 m under the foundations of the nearby housing areas.
After the first breakthrough and disassembly of the TBM, the machine will be reassembled in the launch shaft in Ayazaga to drive a second, 7.29-km long discharge tunnel between the existing wastewater tunnels of Kemerburgaz and Ambarli. Here the ground will be rock and sandstone.