• 001

Within the scope of Kabataş-Mecidiyeköy-Mahmutbey Subway Project, shoring works of NATM, TBM and Turnout shaft in Kabataş, Istanbul has been carried out. The excavation depth of these three shafts vary between 43.10 m to 45.4 m and they are very close to the Istanbul Bosphorus shoreline, therefore special circular shafts were selected as the shoring system. The details of the circular shafts are as follows;

  • Turnout Shaft (Diameter of Shaft: 11 m; Depth of Shaft: 43.1 m)
  • TBM Shaft (Diameter of Shaft: 15 m; Depth of Shaft: 45.4 m)
  • Tail Shaft (Diameter of Shaft: 12 m; Depth of Shaft: 43.9 m)

For the excavation of shafts, two different but integrated shoring systems are applied. A shoring system consists of secant piles socketed into rock within the fill and weak soil layers at the upper elevations; whereas a shoring system consists of reinforced concrete wall supported with soil nails within the rock formation are executed.

Within the scope of the project, a total length of 5,500 m secant piles having a diameter of 65 cm to 80 cm and a length of 16 m to 32 m were constructed for these three shafts. Moreover, the project site is very close to the Bosphorus shoreline and when the project is completed, these shaft excavations will be the deepest and largest circular shafts under water within the shoreline of Bosphorus in Istanbul.

Project Description

Alarko Kabataş Construction Site, Shoring Works of NATM, TBM and Turnout Shaft

  • Engineering

Project Features

Key Quantities
Secant Pile 5,550 m
Project Duration
Start Date 01.07.2016
Finish Date 28.12.2016
Duration 5 Months


Istanbul, Turkey




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