Analysis on geological condition of rock mass with Hoek-Brown strength criterion

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 withthe non-linear Hoek-Brown strength criterion.The Hoek-Brown strength criterion for rock mass is widely accepted and applied in a large numberof engineeringin 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 thegeological condition parameters considered in Hoek-Brown strengthcriterion,disturbed factor D, and intact rock constant m_ion the rock mass strength are studied. The geological conditions of the rock mass areindicated byvolumetric discontinuity frequencyλ_v,infilling ratingR_f,roughness ratingR_r and weathering ratingR_wof the discontinuity and represented by the Geological Strength Index(GSI). To embody the advantageof Hoek-Brown strength criterion, a deeply buried tunnel is involved in numerical analysiswith 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 thewaste of uniformly distributed support structure using global design concept.