ROCK TUNNELLING | ROCK MASS CLASSIFICATION - REVIEW


Above, figure 2: World map of rock mass classification systems (RMCS) for underground application (Tunnelling and Underground Mining). Only pieces of the pie charts with15% of the votes for one country are labelled


more than one RMCS received the same number of


votes for one country, the country is set to “tie” (e.g., Bolivia received only two submissions for the application Tunnels and Caverns resulting in a tie). For all applications, a “tie” is either the second most


frequent or even most frequent situation, thus indicating that there is no best-fitting system for each investigated application. However, GSI is first place for all three different slope-related applications, and Q-slope, RMR, and A-BQ are also among the top systems. Despite the “tie” situations, the Q-system ranks


number one in applications Tunnels and Caverns and Underground Mines followed by RMR. For the application in Foundations, RMR reaches


second position, behind a tie; RQD and GSI follow RMR. This can indicate that rock mass classification plays a subordinated role in foundation engineering and, rather, parameters such as RQD and GSI used for general rock mass characterisation are in use.


20 | June 2025


5 DISCUSSION The world map of rock mass classification (see Figure 2), for Tunnelling & Underground Mining, shows that a large number of RMCS are in use all over the world today. However, we can observe that only a few are majorly used: (a) for slope engineering (GSI, RMR, Q-slope); and, (b) for underground construction (Q, RMR, GSI). Technically comparing these systems (also including


A-BQ due to its dominance in Asian countries) among one another shows that they are considering different parameters that characterise different aspects of the rock mass (see Table 2). All rock mass classification systems consider the


discontinuity density in one way or another (often through RQD), but no other parameter is shared by all. This can be related to the geological background of these systems and, therefore, regional engineering focus points.


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