ABSTRACT: In this study, the relationship between engineering geological applications and tunnel excavationmethods were described. Even if several tunnel excavation methods have been suggested from past upto the present, most of them were only the various derivations of full face and sequential excavationtechniques. Internationally well-known tunnel excavation methods try to classify rock mass behaviors,but, cannot form a numerical base for the claimed methods. Therefore, objective evaluations are required(especially for their applications) to overcome the deficits rock mass classification systems are used.NATM and ADECO-RS are the two widespread methods at the present day tunnel practice. In bothmethods, rock mass behavior has been categorized in different ways. However, both of them failed togenerate objective base to describe the rock mass behavior. In this study, practical difficulties, functionalrelation of commonly used tunnel excavation methods between rock mass classifications systems and theirapplication to numerical models, have been described. For this aim; transition of rock mass classificationsystems to tunnel excavation and support classes, their application to numerical models, their assumptions,and in point of view of the engineering geology; assumption defects have been described with the help ofan example.