ABSTRACT: Rock mass classification systems are used for rock mass characterization and design in the preliminary stagesof many mining activities and engineering applications. There are theoretical and experimental methods for theprediction of tunnel boring machine (TBM) performance in project stage. The correct estimation of machineperformance is influenced by many input parameters of rock mass, and although it is relatively easy to predictmachine performance in isotropic intact rock environments, it is very difficult in poor rock having anisotropicbehaviour. Many studies in this area have shown a poor relationship with penetration and rock mass classifications.In this study, the performance analysis of TBM in anisotropic weak rock environment with the QTBM method, whichis used in the Tunnel No. 26 (between Bilecik and Bozuyuk), located in the Ankara-İstanbul high-speed train line,has been examined in the section until the machine is trapped in the tunnel. It is concluded that there exist problemsfor the anisotropic weak rocks in the QTBM method. It is extremely difficult to estimate the intermittent disk changetime interval in such environments, and the relationship between properties of anisotropic rock mass and machinecharacteristics should be considered together for the performance machine prediction.