A brief history of the development of the Hoek-Brown failure criterion

The Hoek-Brown failure criterion was developed in the late 1970s to provide input for the design of underground excavations. Bieniawski’s RMR was originally used to link the criterion to engineering geology input from the field but a more specific classification system called the Geological Strength Index (GSI) was introduced in 1995. Both the Hoek Brown criterion and the GSI classification have evolved and continue to evolve to meet new applications and to deal with unusual conditions encountered by users.