The Correct Way to use the Hoek-Brown Strength Criterion for Slope Stability Analysis on the Example of Vals (Tyrol/Austria)

Abstract

The Hoek-Brown (HB) strength criterion is increasingly used to investigate the stability of slopes. However, it is still partly unclear how this should be implemented for slopes in a correct way. There are two ways to use the HB strength criterion. On the one hand, the HB parameters can be converted into equivalent Mohr-Coulomb (MC) parameters by estimating a suitable range of minor principal stresses. The result is a linear failure envelope. On the other hand, the nonlinear HB failure envelope can be applied directly by calculating apparent MC parameters for each point of the HB failure envelope. The result is a nonlinear failure envelope. Equivalent MC model parameters are usually used in numerical model calculations. However, this approach has some disadvantages. On the example of Vals, where a rock fall of about 117,000 m³ occurred in December 2017, a new method for using apparent MC parameters is presented.