Turkish construction company Eferay Yapi Ticaret A.S. together with the Canadian-Chinese Lovsuns Tunneling Canada Ltd, celebrated the breakthrough of the 3.91m diameter single shield EPBM being used on a wastewater tunnel in Istanbul in September 2016.
The 3.91m diameter EPBM finished the first 2km long tunnel in Zeytinburnu as part of the Ayvali-2 Tunnel, designed to increase the wastewater capacity of the existing lines in Bagcilar, Esenler, Gungoren and Zeytinburnu. The Tunnel will carry the wastewater from these main hubs of Istanbul to the Yeni Water Treatment Facility.
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The TBM began tunnelling in mid December 2015 from a 21m deep launch shaft and broke through into the 12m deep target shaft after some 9 months of boring. Normally the boring time would have been much shorter, but problems with the muck transportation system during winter slowed progress.
The geology along the drive consisted of sandstone, siltstone, clay and soil with occaisionaly high groundwater. During the last 150m drive, grouting to stabilize the ground helped prevent high water ingresses whilst simultaneously securing the stabiliy of the buildings on the surface.
Thanks to the crew and the machine the best shift showed an advance of 15.6m, the best daily advance was 31.2m, and the best week was 153m of tunnel driven. The best monthly result occured in April 2016 with 512m. The normal overburden was between 8 and 40m, but over the last 150m before reaching the target shaft, the tunnel passed just 6m beneath building foundations.
After this first breakthrough and disassembly of the TBM, the machine will be reassembled in the launch shaft in Ayazaga to drive a second, 7.29km long discharge tunnel between the existing wastewater tunnels of Kemerburgaz and Ambarli. Here the ground will be rock and sandstone.
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 Co. Ltd, LNSS, China based in Toronto), designed by experienced ex-Lovat engineers and manufactured in the modern Chinese facilities of LNSS.