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New correlation Between “Q & RMR” and “N & RCR”

Author:
[ A.R.ASgari ] - Grad..Min. Dep.Isfahan university of technology

Abstract:

There are various correlations between the two most widely used classification indices , the rock mass rating RMR of bieniawski (1973) and the rock mass quality of Barton et al. (1974) The following correlations are based on 115 case histories and proposed by Bieniawski (1), Rutledge and preston (2), Moreno(3) , cameron – clarke and Budavari (4), and Abad et al.(5) RMR = 9 LnQ + 44 (1) RMR = 5.9 LnQ + 43 (2) RMR = 5.4 LnQ + 55.2 (3) RMR = 5 LnQ + 60.8 (4) RMR = 10.5 LnQ + 41.8 (5) And an approach gave by Goel et al. (1996) , propose a new correlation which state that the above equation ignore the fact that the two systems are not truly equivalent. And thus they defiend two new rock mass indices 1: the rock mass number N defined as the rock mass quality with SRF as l; and 2: the rock condition rating RCR defined as RMR without Rating for Joint orientation and intact rock strength . and they proposed a new correlation between N and RCR as followed: CR = 8 LnN + 30 (6) Considering to the above explanation and correlations shows that all these approaches are based on documented case histories. For example Bieniawski used 117 case histories involving 68 scandinavian, 28 south african and 21 other cases. In order to apply the correlation Between Q and RMR to the ‘ ‘iranian geological condition” 47 couple data consisting of RMR and Q and 42 couple date consisting of RCR and N which were picked up directly from various researchers reports were used to obtain two new correlations as follows. [ASGARI, 2000] RMR = 4.2 LnQ + 50.6 (7) RCR = 6 LnN + 45 (8)

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