Hoek - Brown
Hoek-Brown failure criterion describes the failure of a rock mass (based on the performed analyses of hundreds of underground structures and rock slopes) as:
major principal stress during rock failure
minor principal stress during rock failure
strength of the intact rock in simple compression
uniaxial compressive strength of intact pieces of rock
nonlinear material constant depending on the rock quality
coefficient depending on the rock breaking
The basic parameters of the modified Hoek-Brown model should be determined from in-situ and laboratory measurements. To become more acquainted with this model, a brief list of ranges of individual parameters is provided. If rock mass classification using GSI is known then it is possible to let the program determine the H-B parameters by itself.
For actual analysis, the H-B parameters are transformed into the M-C parameters. The solution procedure then becomes identical to that of the Mohr-Coulomb criterion.
For conversion of Hoek-Brown parameters is used solution according to Hoek, Carranza-Torres, and Corkum (2002) in case of the analysis of rock slope stability:
The angle of internal friction φ:
Cohesion (shear strength) c:
The maximum value of a smaller principal stress σ‘3max is given by:
unit weight of the rock
height of the rock slope
strength of the intact rock in simple compression, or uniaxial compressive strength of intact rock mass
Stability analysis of rock slopes with a modified Hoek-Brown failure criterion, ANG Xiao-Li ; LIANG LI ; YIN Jian-Hua International journal for numerical and analytical methods in geomechanics. ISSN 0363-9061, 2004, vol. 28, no2, pp. 181-190.
Hoek E, Carranza-Torres CT, Corkum B.: Hoek–Brown failure criterion—2002 edition. Proceedings of the 5th North American Rock Mechanics Symposium, Toronto, Canada, vol. 1, 2002, pp. 267 – 273.