A methodology of using past experiences in the performance prediction of a TBM in a complex geology

Uskudar-Umraniye-Cekmekoy-Sancaktepe metro line of 20 km having two tubes is recently commissioned to Dogus Construction Company by Istanbul Metropolitan Municipality Authorities and it is intended to finish in 38 months. The geology is complex consisting of sandstone, arcosic sandstone mudstone, siltstone, shale, limestone, andesite, and quartzitic conglomerate. The geologic units are frequently cut by andesite dykes having significantly fractured contact zones. The area is highly populated, and the overburden changes between 10-80 m. It is predicted that in some areas it is likely that ancient water wells exist which may cause some severe settlement problems. Two TBMs having diameters of 6.57 m already used in Kadikoy-Kartal metro tunnels are refurbished for the tunnel excavations. Uskudar station will be excavated under sea level. The paper describes briefly the methodology based on the accumulated data from previous experiences for TBM performance prediction to identify critical zones for TBM excavation. It is believed that the concept behind of proposed methodology will serve a sound basis for decision making for similar projects coming very soon.