Squeezing Mechanism in a Large Tunnel Constructed i n Weak Rock Mass

Abstract: Unexpected and severe deformations occurred during the excavation in the T15 tunnel constructed in Ankara-İstanbul High Speed Railway Project. As a result of these deformations, failures occurred in the tunnel supports and the tunnel lost its stability. Deformations occurred between Km: 191 + 080 - 191 + 300, and 50 cm deformations were measured. Due to the closures, cracks occurred in the longitudinal direction at the junction of the upper half and lower half in the shotcrete and failures were observed in the bolt plates. The scope of this study is to explain the possible causes of severe deformations excavated in graphite schists. In addition, the results of the numerical analyses are discussed.