Comparison among different criteria of RMR and Q-system for rock mass classification for tunnelling in Korea

Recent increase in the number of tunneling projects in Korea resulted in a large amount of good quality data such as RMR and Q-value for the assessment of rock mass class. In addition, a new bidding system, so-called Turn-Key system, has also made the data quality better than ever before, due to the increase of the budget for site investigation. A conventional guideline for rock mass classification by KHC (Korea Highway Corporation) has been widely used in Korea but other forms of classification using different criteria of RMR or Q-value have been recently used. Since there have been few studies on the relationship among such different criteria on RMR or Q-value, this study mainly focuses on the comparison of the conventional guideline for rock mass classification with several individual classification schemes in Korea. Analysis of the coincidence among the different criteria using both RMR and Q-value showed that there is higher coincidence if rock mass is in relatively good condition. It was also found that there is less consistency between RMR criteria and Q-value criteria in conventional KHC Guideline for rock mass classification than the recently adopted individual criteria. (C) 2002 Elsevier Science Ltd. All rights reserved.