Discussion on the paper entitled "Quantitative assessments of the correlations between rock mass rating (RMR) and geological strength index (GSI)" by Qi Zhang, Xianbin Huang, Hehua Zhu and Jianchun Li, Published in Tunnelling and Underground Space Technology (2019) 83:73-81

The rationality of formulas 22, 27 and 28 in the paper by Qi Zhang et al. (2019) were discussed due to its derivation process. The reason for this irrationality was analyzed in detail and the relationship between RMR89 and RMR14 under the condition of considering only discontinuities of rock mass was extracted. On this basis, a more reasonable formula has been proposed to replace formula 22. And another new relationship between RMR89 and GSI considering strength of intact rock and groundwater has also been put forward. The case study shows that the two formulas proposed in this discussion are applicable.