Joint Slope Stability Analysis Using SSR

1.0 Introduction

This tutorial introduces how to add a joint surface onto a slope and conduct slope stability analysis using the Shear Strength Reduction (SSR) method in RS3.

All tutorial files installed with RS3 can be accessed by selecting File > Recent > Tutorials folder from the RS3 main menu. The initial file of the tutorial can be found in Joint slope stability SSR - starting.file.rs3v3 and the finished tutorial can be found in the Joint slope stability SSR - final.rs3v3 file.

2.0 Starting the Model

1. Select File > Recent > Tutorials Folder.
2. Open Joint slope stability SSR - starting file.rs3v3.
3. Open the Project Settings dialog by selecting Analysis > Project Settings
4. Select the Shear Strength Reduction tab and make sure that the Shear Strength Reduction analysis option is enabled by checking the 'Determine Strength Reduction Factor'.
   1. Initial Estimate of SRF = 1
      
   2. Step Size of Automatic Selected
   3. Tolerance (SRF) = 0.01
      
5. Click OK to close the dialog.

3.0 Model Setup

1. Ensure the Geology workflow tab is selected
2. This model consists of three different types of rock mass defined by Zone I, Zone II and Zone III material properties assigned to the upper, middle and lower portion of the slope.
3. It also consists of a joint surface striking parallel to the slope.
   

4.0 Restraints

1. Select the Restraints workflow tab
2. Select the Faces Selection option from the toolbar. While holding CTRL, select the front faces (XZ) of the model as shown below:
   
3. Select Restraints > Add Restraints/Displacement > Restrain Y.
4. In the Add Restraint dialog, click OK. Now you will see the assigned restraints on the front of the model as shown below:
   
   
5. Do the same for the back face (XZ) of the model by rotating the 3D view cube.
6. Now select the left and right-side faces (YZ) of the model as shown below:
   
   
7. Assign XY restraints by selecting Restraints > Add Restraint/Displacements > Restraint XY.
8. In the Add Restraint dialog, click OK.
9. Now, select the bottom face and assign restraint XYZ by selecting Restraints > Add Restraints/Displacements > Restraint XYZ. In the Add Restraint dialog, click OK. Then, you will see the following restraints as shown below.
   

5.0 Mesh

1. Next, we move to the Mesh workflow tab
2. Select Mesh > Mesh Settings.
3. Use the following settings:
   1. Element Type = 4-Noded Tetrahedra
      
   2. Mesh Gradation = Graded
4. Select Mesh to mesh the model.
   

The mesh is now generated, your model should look like the one below.

Now we will compute the model.

6.0 Compute

1. Next, select the Compute workflow tab
2. From this tab, we can compute the results of our model. Before commencing the stress analysis computation, it is recommended to save the final model as a separate file so that you can access the original file anytime. You can do this by selecting File > Save As.
3. Select Compute > Compute

7.0 Results

1. Once the computation is complete, select Results workflow tab
2. In the legend, change Data Type to Total Displacement and under the SRF drop-down menu change it to 1.9.
The SRF text colour indicates the model has failed if it's red.
3. Select Interpret > Show Exterior Contour
   1. As shown below, the critical zone of failure occurs in the volume of material that is sliding along the joint surface.
      

This concludes the tutorial on jointed slope stability analysis using SSR in RS3.