Hoek-Brown

The Hoek-Brown is an empirical criterion which is used to model the behavior of a jointed rock mass (which can be considered homogeneous and isotropic)  in a response to induced stresses. The criterion is formulated in terms of principal stresses. The criterion first starts from the properties of intact rock and then introduces factors to reduce these properties based on the basis of characteristics of joints in a rock mass.

Hoek-Brown failure criterion includes rock strength dependency on confining pressure which makes it more adequate than Mohr-Coulomb failure criterion.

Applicable Modules:

General Parameters

Modulus of Elasticity (E)

The slope of the stress-strain line for a linear isotropic material.

Poisson's Ratio (u)

The ratio of the radial (or lateral) strain to the vertical strain.

Temperature Coeff. (α)

The relative change of a physical property when the temperature is changed by 1 K.

Unit Weight (Υt)

The weight of soil per unit volume.

Saturated Unit Weight (Υsat)

The weight of saturated soil per unit volume.

Earth Pressure Coeff. (Ko)

The ratio of horizontal principal effective stress to the vertical principal effective stress.

Draining Condition

Drained

Dissipation of pore water pressure takes place upon the load application.

Undrained

Dissipation of pore water pressure does not take place upon the load application.

Skempton 'B' Coefficient

Enter the value of the coefficient for an 'Undrained' condition.

Additional Parameters

Initial m

Yield surface parameter m (frictional) before failure.

Initial s

Yield surface parameter s (cohesive) before failure.

Residual m

Yield surface parameter m (frictional) after failure.

Residual s

Yield surface parameter s (cohesive) after failure.

Unconfined Comp. Strength

Unconfined compressive strength.

Safety Factor Calculation

The safety factor is calculated on the basis of the ratio of the current state of stress of the material to the Mohr-Coulomb failure criterion.  The Mohr-Coulomb failure criterion is most widely used criterion for brittle materials like ground.  SoilWorks uses the criterion for all the material models in the Tunnel Module.