ERAMCA Project Reference: 609574-EPP-1-2019-1-IT-EPPKA2-CBHE-JP

Geological Strength Index – GSI

The Geological Strength Index (GSI), introduced by Hoek (1994), Hoek et al. (1995) and Hoek and Brown (1998) provides a system for estimating the reduction in rock mass strength for different geological conditions as identified by
field observations. The rock mass characterisation is straightforward and it is based upon the visual impression
of the the rock structure, in terms of blockiness, and the surface condition of the discontinuities indicated by joint…