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Generalized Anisotropic

The Generalized Anisotropic Strength option allows you to create a composite material model in which you can assign any strength model in Slide2 to 1) any range of slice base orientations or 2) any set of anisotropic surfaces. For example, you could create a material with Hoek-Brown properties over a range of orientations or along a surface, and Mohr-Coulomb properties over another range of orientations or along a surface (e.g. to simulate a weak bedding orientation in a rock mass).
To define a Generalized Anisotropic Strength function set the Strength Type = Generalized Anisotropic in the Define Material Properties dialog. You will notice two Input Type options, as explained below.

Input Type = Angle Range

This is the original Generalized Anisotropic function option. The user can input angle ranges and assign a material to each range.

Define generalized anisotropic strength function

  • The FIRST angular range always starts at –90 degrees (this is the default value of the FIRST Angle From value, and cannot be edited by the user).
  • The angular ranges must be ordered counter-clockwise, from –90 to +90.
  • The Angle From values cannot be edited, and are automatically defined by the Angle To value in the previous row.
  • The LAST angular range always ends at +90 degrees (this must be entered by the user, as the LAST Angle To value).
  • As the data is entered, the chart at the right of the dialog, will be updated to display the Generalized Anisotropic Function you are defining.
  • Check the chart carefully, to make sure that you have defined the intended function (i.e. all angular ranges and materials are correct).

Input Type = Angle or surface, A, B

Two additional methods of defining anisotropy are found within this option. For users of Slide3, this option will be recognizable as the Generalized Anisotropic strength function in Slide3. The inputs are outlined below.

Define Generalized Strength Function dialog

  • Base Material: this represents the strength properties of the rock mass, for failure planes which are not within the defined orientation range of the anisotropic plane(s) or surface(s).
  • Anisotropy Definition: This can be angle or surface. The two are outlined in detail below.

Anisotropy Definition = Angle

This is similar to the Input Type = Angle Range option, but with the additional inputs of A and B. As an example, we will explain the meaning of the previous image.
In the function, the user has set the base material to Material 2, and defined an angle of 45 degrees for Material 3. This means that if the slice base falls along a 45 degree angle, the strength of Material 3 will be applied, otherwise the strength of Material 2 will be applied.
However, so as not to be so limited to the exact 45.0 degree angle, the A and B values are used to provide a range. The A value means that Material 3 will be applied within the range of [Angle +/- A], or [45 +/5]. The B value means that the strengths of the base material and Material 3 will be interpolated in the ranges [Angle + A, Angle + B] and [Angle - A, Angle - B], or [45+5, 45+10] and [45-5, 45-10]. In summary the above screenshot can be translated to this definition of anisotropy:

  • Strength of Material 3 is applied for slice base in these angle ranges:
    • [40, 50]
  • Strength of Material 2 is applied for slice base in these angle ranges:
    • [-90, 35]
    • [55, 90]
  • Interpolated strength of Material 2 and Material 3 is applied for slice base in these angle ranges:
    • [50, 55]
    • [35, 40]

A and B are explained in more detail in the Anisotropic Linear Strength topic.

    Anisotropy Definition = Surface

    This option allows the user to define multiple anisotropic surfaces and assign different materials to each one. The point on the anisotropic surface that is closest to the given slice base is found, and the angle of the anisotropic surface at that point is taken as the angle of anisotropy for the given slice base. Once the angle is obtained, the calculations proceed as explained in the previous section.
    The way the Anisotropic Surface works is explained in detail in the Anisotropic Linear Strength topic. Note that you must first use the Add Anisotropic Surface option to define an anisotropic surface before being able to access this option.
    Note on multiple Anisotropic Surfaces:If more than one anisotropic surface has been defined, the algorithm first determines which anisotropic surface is nearest to the orientation of a given slice base. Then the calculation proceeds as usual, only considering the nearest anisotropic surface. Other anisotropic surfaces are ignored.

    Additional Notes

    A Generalized Anisotropic material (herein referred to as the "parent" material) can be defined to have differing base and joint material properties, which are herein referred to as "child" materials.

    • The functions defined with each input type create two separate lists. For example you may have a list of two functions defined with Input Type = "Angle Range" which you can access from the dropdown when the Angle Range type is selected. You will see a different list and set of functions when the Input Type = Angle or Surface, A, B is selected.
    • You cannot assign a Generalized Anisotropic function to itself.
    • With Input Type = "Angle Range", no interpolation of material strengths occurs as does with the other Input Type on account of A and B. As a result, the water properties are used differently. Input Type = "Angle Range" uses the water properties of the child material that is used in the given angle range. Input Type = "Angle or Surface, A, B" uses the water properties of the parent material (the Generalized Anisotropic material itself)
    • The unit weight of the parent material will be used to calculate the weight of a slice.
    • The design factors specified in the Project Settings relating to material strength will be applied onto the child materials.
    • Due to the algorithmic difference between the two Input Types, equivalent anisotropic definitions in the two types may exhibit a negligible numerical difference in FS.
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