ABSTRACT: In terms of geological engineering, tunnel design in weak rock masses presents some challenges.A small misinterpretation in the design stages can lead to costly and time-consuming problems at theconstruction phases. To avoid serious problems of these kinds, tunnels excavated in weak rock massesshould be projected with the most suitable and economical excavation method in design stage. In thisstudy, stability of the thin-bedded marls belong to Paleocene aged Şenkaya Sırtı formation, outcropped onthe route of Cankurtaran (Hopa-Artvin) tunnel, was investigated using empirical and numerical methods.Firstly, the properties of the discontinuities in the marls and geomechanical parameters of intact rockmaterial were determined based on the description criteria of ISRM (1981). In the next stage, marlswere classified by using the RMR, Q and GSI systems and rock mass properties were determined. In thefinal stage, the stability of the tunnel, planned to be excavated in the marls, was investigated by usingthe criterion of Singh et al. (1992), Goel et al. (1995), Bhasin and Grimstad (1996) and Finite ElementMethod (FEM). As a result of the analyses, it was concluded that the factor of safety value varies between0.08 and 1.43 and there may be a risk of instability problem in the tunnel.