TBM cutting performance in Istanbul

The Tarabya tunnel forms a major part of a sewerage project currently under construction in Istanbul, Turkey, designed to clean up the unacceptable pollution present in the Istinye - Tarabya and Büyükdere bay areas of the city's Bosphorus River. The tunnel is 13,270m long with an i.d. of 2m and is situated between Sariyer in the north and Baltalimani in south. Some limestone samples were taken form the tunnel face in September and November 2000 for testing in the laboratory. These were thought to be representative of the geology along the majority of the alignment and were subjected to full-scale laboratory cutting tests using one of the TBMs disc cutters. The relationship between thrust force and depth of cut recorded in the lab was compared to those obtained in the field to assist future research into machine utilization. The compressive strengths of the samples were found to be 80±7MPa and 119±16MPa respectively.