Orthotropic Strength

When calculating stress and failure using the orthotropic strength option, the intrinsic load-bearing capacity of the rock is modeled as a function of angle with respect to the weakness plane. In the calculations, the strength is modeled as a function of angle with respect to the weak planes, and is scaled directly to the strength of the intact rock.

Anisotropic rock has a strength when loaded perpendicular to the bedding defined by the isotropic model. The strength parallel to bedding and at 45 degrees to bedding is defined by two parameters, A and B (both of which are generally assumed to be less than or equal to 1), that must be derived by fitting laboratory experimental data. The value of A is less than one, corresponding to a strength parallel to the weakness planes that is smaller than the strength perpendicular to bedding; the value of B is less than that of A.

An example: the parameters A=0.6 and B=0.4 indicate that when the load is applied along the bedding planes, the strength is 0.6 times the strength when the load is applied perpendicular to bedding, and the strength is 0.4 times the strength when the load is applied 45 degrees to the bedding planes (A=B=1 is an isotropic rock).

To specify orthotropic strength:

Upon opening the form, for both parameters the 'use constant' option is selected and a value is already entered. If these are the values that you want to use for the calculations, click OK to save the settings and close the form.

If necessary, update the values for your parameters, and click OK to save your settings and close the form.

Optionally, you can deselect the 'use constant' option, and select a log from the drop-down list. Click OK to save your settings and close the form.