Performance of EPB TBM in Beylerbeyi-Kucuksu Wastewater Tunnel in Istanbul
Utilization of TBMs is unavoidable for tunnels considered in urbanized areas to realize fast and cheaper construction and excavation performance of TBMs is very crucial for economy of these projects. Terminology on excavation performance of TBMs includes generally daily and monthly advance rates, instantaneous penetration rates, cutterhead torque requirements, TBM thrust requirements, machine utilization times, cutter consumption rates, as well as problems and stoppages encountered during excavation. These parameters should be controlled to obtain a successful project during the whole excavation and construction operation. The basic parameters affecting excavation performance of a TBM operation can be classified into 3 general groups as seen in Table 1 (Bilgin et al., 2014): a) geological and geotechnical, b) excavation machine (TBM) related, and c) operational parameters. Among them, the geological and geotechnical parameters are the most important ones. The machine related parameters should be arranged / designed according to the expected geological and geotechnical conditions for the best excavation performance and minimum cost. The excavation performance in construction of Beylerbeyi-Kucuksu Wastewater Tunnel aligned along the Istanbul Strait is summarized in this study in relation to geological-geotechnical conditions, as well TBM operational conditions. The tunnel having a length of 4,344 m and finished diameter of 2.2 m is excavated by an Earth Pressure Balance TBM with 3.25 m excavation diameter. The project owner is Istanbul Water and Sewage Authority (ISKI) and the contractor is Unal Akpinar Construction Inc.