Analysis and Remediation of the Structurally Controlled Rock Failures During Tunneling: a Case Study Along the Black Sea Coastal Highway in Northern Turkey

In this study, the stability assessment and the analysis of the structurally controlled rock failures in the Geçilmez tunnel, which was constructed in Giresun, along the Black Sea coastal highway was performed. The rock mass classification of the tunnel grounds was completed and the geomechanical parameters that were necessary for the stability analysis and for the design of the tunnel were determined. The structurally controlled instabilities, i.e., inactive probable faults and shear zones within the tunnel sections were identified and wedge stability analysis was utilized to determine the potential wedge failures that could possibly occur during tunneling and to apply the necessary support systems for stabilizing any wedge failure in the tunnel. The induced stress distributions and deformations in the rock mass surrounding the tunnel grounds was investigated and the interaction of the support systems with the rock mass was analyzed by using finite element modeling to check the validity of the empirical preliminary tunnel support requirements and also to compare the results with those obtained through assuming structurally controlled failures during tunneling. The results of the structurally controlled failure analyses and numerical analyses were compared in an attempt to determine the preliminary tunnel support systems to stabilize the Geçilmez tunnel.