Anisotropy - One Plane

1.0 Introduction

This tutorial introduces the model creation of a simple geometry slope with homogeneous single anisotropic plane. The Generalized Anisotropic Strength function feature is used in this tutorial.

More details on the parameters used in this tutorial and the theoretical background of the function can be found here: Generalized Anisotropic Overview.

2.0 Material with Single Anisotropic Plane

1. Select File > Recent > Tutorial in the menu and open the file Anisotropy - One Plane.

2. The model is a single material 3D extruded slope.

3. Select Materials > Define Materials or Define Materials from the toolbar.
4. Notice the 3 materials defined: anisotropic material, rock mass, anisotropic plane.

5. For the anisotropic material, select the Edit button beside the Generalized Function combo box.
6. Make sure the following parameter values are entered.
• Anisotropy Definition = Dip/DipDirection
• Only one anisotropic plane is defined
• Dip = 20 degrees (dip of anisotropic plane)
• Dip Direction = 0 degrees (same as the Dip Direction of the slope)
• A parameter = 10 degrees
• B parameter = 20 degrees
• Base Material = “rock mass”
• Anisotropic plane Material = “anisotropic plane”

3.0 Results

1. Run Compute
2. Select the Results tab
3. Turn on the contour plot by selecting Show contours from toolbar.

For the Janbu method, the global minimum surface should appear as follows. Factor of Safety is around 1.1. Base Normal Stress contours are displayed in the following figure.

Tightness of Anisotropy

The A and B parameters control the tightness of the anisotropy. Smaller A and B parameters give a narrower range of possible angles for the anisotropic strength plane. This results in different critical surfaces and safety factors.

Re-run the above model, with the following parameters for the anisotropic plane:

• A = 5 B = 10
• A = 5 B = 15

And compare with the above results.

A and B parameters should not be too small, or else the search methods may not be able to locate the plane of anisotropy, if the plane orientation is too narrowly defined.

Effect of Anisotropy

To demonstrate the effect of the anisotropic plane, re-run the above model using only the “rock mass” strength assigned to the slope material (i.e. switch the material type from Anisotropic to rock mass).

You will see the critical surface and safety factor is quite different. Factor of safety (Janbu) is about 2.8.

This concludes the Slope with Anisotropy - One Plane tutorial.