Rocks
In the Rocks subnode you define the properties for modeling materials with failure criteria representative of rocks. This material model can be used together with Linear Elastic Material and Nonlinear Elastic Material. It is available with the Geomechanics Module. The Rocks subnode is available for 3D, 2D, and 2D axisymmetry.
When a Rocks node is present, an Equivalent Plastic Strain plot is available under Result Templates.
The failure criteria are described in the Structural Mechanics Theory chapter:
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Original Hoek–Brown Criterion
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Generalized Hoek–Brown Criterion
Rock Model
Select the Material model — Original Hoek–Brown or Generalized Hoek–Brown. The default values for the material parameters are taken From material. For User defined choices, enter other values or expressions.
Original Hoek–Brown
The defaults for the Compressive strength σcs, Hoek–Brown parameter m, and Hoek–Brown parameter s are taken From material.
Generalized Hoek–Brown
The defaults for the Compressive strength σcs, Geological strength index GSI, Disturbance factor D, and Intact rock parameter mi are taken From material.
Tension Cutoff
If required, select either None or Principal stress cutoff.
When Principal stress cutoff is selected from the list, enter a value or expression for the Maximum tensile stress σt. Use this to constrain the rock model with an extra yield surface, which limits the maximum principal tensile stress.
See also Tension Cutoff in the Structural Mechanics Theory chapter.
Advanced
To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog.
Select the Local method to solve the plasticity problem — Automatic or Backward Euler. When Backward Euler is selected, it is possible to specify the maximum number of iterations and the relative tolerance used to solve the local plasticity equations. Enter the following settings:
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Maximum number of local iterations. To determine the maximum number of iteration in the Newton loop when solving the local plasticity equations. The default value is 25 iterations.
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Relative tolerance. To check the convergence of the local plasticity equations based on the step size in the Newton loop. The final tolerance is computed based on the current solution of the local variable and the entered value. The default value is 1e-6.
See also the Numerical Integration Algorithm section in the Structural Mechanics Theory chapter.
Location in User Interface
Context Menus
Solid Mechanics > Linear Elastic Material > Rocks
Solid Mechanics > Nonlinear Elastic Material > Rocks
Ribbon
Physics tab with Linear Elastic Material or Nonlinear Elastic Material node selected in the model tree:
Attributes > Rocks