The paper analyses the research an rock mass classifications in engineering design. The parameters used and the classification structures of the RSR-, RMR- and Q-systems are reviewed. The paper presents as a concept that the classification of rock masses for engineering purposes can be represented by a weighted engineering matrix and a universal rock mass evaluation matrix. A short reasonable explanation to the relationship between classifications is given. The classification parameters affecting underground engineering design are studied and an example of interactions between them is represented.
