Jethwa, J.L and Goel, R. K. (1995) Indian Experiences with Q and RMR Systems. Tunnelling and Underground Space Technology, 10 (1). pp. 97-109. ISSN 0886-7798

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The Q-systemir, of Barton et. al. (1974, 1975) and the RMR-system of Bieniawski (1973) have been evaluated on the basis of measured tunnel support pressures from 25 tunnel sections, 2 to 14 m wide, covering both squeezing and non-squeezing ground conditions. The comparison shows that the Q-system is unsafe for large tunnels under squeezing ground conditions. A new correlation has been developed considering tunnel depth, tunnel radius, tunnel closure, and Rock Mass Number- i.e., "stress free Q”- to obtain reliable estimates of tunnel support pressures. Changes suggested by Sheorey (1991) for satisfactory application of the Q system to coal-mine roadways on the basis of 44 case histories are presented. Unal’s (1983) correlation for coal-mine roadways is shown as overly safe for large tunnels under non-squeezing ground conditions, and unsafe for all sizes of tunnels under squeezing ground conditions. Correlations between tunnel support pressure, tunnel depth, tunnel closure, and Bieniawski's RMR have been developed to provide reliable tunnel support pressures for all sizes of rock tunnels under varying ground condition. The correlations between RMR and Q proposed by Bieniawski (1976) and by Rutledge and Preston (1978) are not reliable, because RMR and Q are not truly equivalent. Therefore, an acceptable correlation between rock mass number N and RMRmod, i.e., RMR without joint orientation and intact rock strength, has been presented for a better interrelation.

Item Type: Article
Subjects: Blasting
Depositing User: Dr. Satyendra Kumar Singh
Date Deposited: 21 Jan 2012 11:36
Last Modified: 21 Jan 2012 11:36

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