The following parameters are calculated for the Generalized Hoek-Brown criterion.
Parameters mb, s, a
For a given set of input parameters (sigci, GSI, mi and D), RocData calculates the parameters of the Generalized Hoek-Brown failure criterion (mb, s and a), using the equations given in the Generalized Hoek-Brown topic. Results are displayed in the Sidebar as shown below.
Rock Mass Parameters
The following rock mass parameters are calculated for the Generalized Hoek-Brown criterion:
Sigt (rock mass tensile strength)
Sigc (uniaxial rock mass compressive strength)
Sigcm (global rock mass compressive strength)
Em (rock mass modulus of deformation)
NOTE1: tensile and compressive strengths are calculated using equations given in Hoek, Carranza-Torres and Corkum (2002). Note that there are two values of rock mass compressive strength – sigc and sigcm. For a discussion of how these two parameters are defined, and how they may be used, please see Hoek, Carranza-Torres and Corkum (2002) – section 5: Rock Mass Strength.
NOTE2: rock mass modulus is calculated according to the Modulus Estimation Method which is selected in Project Settings. See the Rock Mass Modulus topic for details.
Curve Fit of Test Data
If you are analyzing triaxial test data with the Hoek-Brown criterion, the following parameters are calculated from the curve fit:
For intact rock data, the parameters mi and sigci are calculated.
For rock mass data, the parameters mb, s, a, mi, GSI are calculated.
See the Triaxial Lab Data and Triaxial Field Data topics for more information.
Equivalent Mohr-Coulomb Parameters
For the Generalized Hoek-Brown envelope, an equivalent Mohr-Coulomb (linear) envelope is automatically calculated over a user-defined stress range, and the best-fit parameters (cohesion and friction angle) are displayed in the Sidebar. See the Equivalent Mohr-Coulomb Parameters topic for more information.