Page 365 - Engineering Rock Mass Classification_ Tunnelling, Foundations and Landslides

320 Engineering Rock Mass Classification

FIGURE 26.1 Estimate of GSI based on visual inspection of geological conditions. (From Roclab,
2006; Marinos and Hoek, 2000) Modification by Cai et al. (2004) in terms of its quantification by block
volume and joint condition factor is also shown on the right side.

These classifications have been available to engineers and geologists for 60 years. Dis-
continuities are classified into five surface conditions that are similar to joint conditions
in RMR (Chapter 6).
1. Very good
2. Good