Abstract: The Hoek-Brown failure criterion for determination of non-linear shear strength of rock mass has been under constant upgrading during the past two decades. The latest 2018 version summarizes the main issues on utilizations and key factors of this system. One major concern of using this system comes from the appropriate selection of the disturbance factor D that ranges from 0 to 1, covering the applications in tunneling and slope engineering with conditions varying from well controlled to uncontrolled excavations. This paper focuses on the values of D that best fits the application in hydro-slopes, normally excavated under controlled blasting works. The main approaches include the comparisons between GSI-1995 and GSI-2018 versions. The former has been suggested in China’s hydro-slope design standard. A simple test example was investigated by varying its geometry and physical parameters, with the finding that D ranges from 0.78 to 0.88 as the two versions offer the same factor of safety. Three engineered slopes of hydropower projects that originally adopted GSI-1995 version were investigated. The calibration work that equivalents the two versions suggests that D ranges from 0.72 to 0.85. The authors then suggest adopting D ranging from 0.7 to 0.9 for hydro-slope design.

Key words: Hoek-Brown failure criterion, disturbance factor, GSI method, stability analysis, hydro-slope engineering