Geotechnical investigation of the service shaft-2 opened in the new Zigana (Torul-Gümüşhane) tunnel

In this study, the stability of service shaft-2 opened in the New Zigana (Torul-Gümüşhane) Tunnel was investigated using empirical, analytical and numerical analysis methods. In order to define rock masses, RMR, Q and GSI systems were used as empirical methods. Rock-Support Interaction and Convergence Confinement Methods were used in the analytical analysis of the shaft stability. In order to determine the plastic zones occurred around the unsupported shaft walls, the finite element (FEM) based 2D and 3D numerical models have been used. The results obtained from these analysis methods were compared and their compatibility was investigated. According to the results of the empirical analysis, there is no need to support for the stability of the shaft. However, analytical and numerical methods are more conservative and suggesting support application for the stability. According to convergence-confinement and 2D analysis, the plastic zone around the shaft walls developed after the depth of 105 m. and 81 m., respectively.