Fig. 3From: Estimating in situ rock mass strength and elastic modulus of granite from the Soultz-sous-Forêts geothermal reservoir (France)(Modified from Marinos et al. (2005))Chart for obtaining geological strength index (GSI). The positions of the three 25 m-interval rock masses from Fig. 6 are shown on the chart. Note that the highest and lowest category should not be used for the generalised Hoek–Brown failure criterionBack to article page