1. Balmer G (1952) A general analytical solution for Mohr’s envelope. Am Soc Test Mater 52:1269–1271
2. Barton N (2002) Some new Q-value correlations to assist in site characterization and tunnel design. Int J Rock Mech Min Sci 39:185–216
3. Bieniawski ZT (1974) Geomechanics classification of rock masses and its application in tunnelling. In: Proceedings of the third congress of the international society for rock mechanics. Denver, pp 23–32
4. Bieniawski ZT (1979) The geomechanics classification in rock engineering applications. In: Proceedings of the fourth congress of ISRM, vol 2, Montreux, pp 41–48
5. Boyd RD (1993) Elastic properties of jointed rock masses with regard to their rock mass rating value. In: Cripps JC et al (eds) The engineering geology of weak rock. Balkema, Rotterdam, pp 329–336