Most of the numerical analyses currently used for evaluation of the stability of underground excavations are based on a linear Mohr–Coulomb strength criterion. However, experimental data and experience of the field engineering showed that the strength of nearly all types of rock mass followed with the non-linear Hoek–Brown strength criterion. The Hoek–Brown strength criterion for rock mass is widely accepted and applied in a large number of engineering in the world. This paper briefly introduces Mohr–Coulomb strength criterion and Hoek–Brown strength criterion as well as the parameters considered in the two strength criterion. The effects of the geological condition parameters considered in Hoek–Brown strength criterion, disturbed factor D, and intact rock constant mi on the rock mass strength are studied. The geological conditions of the rock mass are indicated by volumetric discontinuity frequency λv, infilling rating Rf, roughness rating Rr and weathering rating Rw of the discontinuity and represented by the Geological Strength Index (GSI). To embody the advantage of Hoek–Brown strength criterion, a deeply buried tunnel is involved in numerical analysis with GeoFBA3DV2.0. The numerical result reflects the superiority that Hoek–Brown strength criterion can consider the instant and sectional geological condition with the link of GSI. Tunnel design with Hoek–Brown strength criterion can use the accurate surrounding rock parameters following the tunnel excavation and avoid the waste of uniformly distributed support structure using global design concept.
Analysis of a variety of problems in rock mechanics and rock engineering requires determination of the rock mass strength. Over the past decades, several different strength criteria have been developed for rock and rock mass. Most of the numerical analyses currently used for the evaluation of the stability of underground excavations or rock slope are based on a linear Mohr–Coulomb strength criterion (Hoek 1990). The Mohr–Coulomb strength criterion is widely used because of its simple expression of liner equations in principal stress space and easy determination of its parameters.