An assessment on the inner lining need for a large-span tunnel (a case from Turkey, Akyazı Tunnel, Trabzon)

Abstract Stability of large underground structures depends on not only rock mass conditions but also excavation stages and support systems. In addition, complexity geological interaction with in situ affect the performance design. The Akyazı tunnel (Trabzon, Turkey) is 2478 m long was designed as 3 lanes double tubes, number at junction part increases to 5. Tunnel cross-sectional area from reaches 150 2 5 438 gradually. width point 31 m. this study, necessity inner lining concrete tunnels excavated good assessed results analyses are discussed. cost construction, well extending construction period. With procedure followed tunnel, top heading constructed without lining. No stability drainage problem have been encountered for 4 years. Currently, completed successfully, opened traffic. Consequently, stages, systems described, especially necessities discussed study may be applicable extremely sections.