Tunnels and underground structures are one of the most important engineering projects in the country, So they have always faced many challenges that are directly related to the characteristics of the rock mass. Rock mass classifications can be useful in evaluating and interpreting rock mass behavior. One of the most important tasks of the classifications is to the behavior of the rock mass in the face of the underground space to estimate the reinforcements and stabilization of the tunnel. But these classifications alone cannot reflect all the characteristics of the rock mass and have a complete interpretation of the behavior of the rock mass. Thin-layer rocks are one of the major challenges in the implementation of engineering projects, and the use of a classification cannot have a proper interpretation of its behavior. The results show that when dealing with thin-layer rocks, the combined use of the results of RSR, Q, modified RMR and RMI classifications, and especially the modified RSR and RMR classification, can provide a real interpretation of the conditions of the thin-layer rock mass. The results show that the RMR classification does not have a correct interpretation of the rock behavior and cannot predict and evaluate the consolidations well. The use of combining the numerical results with stress analysis and finite element method as well as the formula calculation of reinforcements also have a good compatibility with the results of the stated classifications, but it does not have a correct combination with the results of the RMR classification.