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09 - Trim Joints

1.0 Introduction

In this tutorial a steep cut is made in a sedimentary formation hosting a dike. While the sedimentary rock is highly jointed, the dike is mostly intact except at the interfaces. The joints in the sedimentary formation are represented as a discrete fracture network (DFN) and imported into RocSlope3 in .dxf format. Its extents are trimmed such that the DFN only populates the sedimentary formation and not the dike. Joints are also applied at the dike-host interfaces, which can serve as potential planes of failure.

Finished Product

The finished product of this tutorial (Trim Joints.rocslope_model) can be found in the Trim Joints folder. All tutorial files installed with RocSlope3 can be accessed by selecting File > Recent Folders > Tutorials Folder from the RocSlope3 main menu.

2.0 Starting a Model

Open RocSlope3. You will see a blank workspace.

2.1 Project Settings

The first step to any RocSlope3 project should be to review and configure the analysis parameters for model in the Project Settings.

  1. Select Analysis > Project Settings or click on the Project Settings Project Settings icon icon in the toolbar.
  2. Select the Units tab and set Units to Metric, stress as MPa.
    Project Settings Units
    Units Tab in Project Settings Dialog
  3. Select the Analysis tab.
    1. Set Design Factor of Safety = 1.0
    2. Set Successive Failure = ON.
  4. Project Settings Analysis tab
    Analysis Tab in Project Settings Dialog
  5. Click OK to save the Project Settings and to close the dialog.

These project settings are configured to run a deterministic block stability analysis considering successive block failure.

3.0 Defining Material Properties

Define the Material Properties

  1. Select Materials > Define Materials. By default, three Material Properties (Material 1, Material 2, and Material 3) are defined in the Define Materials dialog.
  2. Select Material 1.
    1. Enter Name = Limestone.
    2. Set Unit Weight = 0.026 MN/m3.
    3. No Water Surface applied.​
  3. Limestone Material Property in Define Materials Dialog
    Limestone Material Property in Define Materials Dialog
  4. Select Material 2.
    1. Enter Name = Granite.
    2. Set Unit Weight = 0.027 MN/m3.
    3. No Water Surface applied.
  5. Granite Material Property in Define Materials Dialog
    Granite Material Property in Define Materials Dialog
  6. Select Material 3
    1. Click the Delete Delete icon button on the bottom-left of the dialog to delete Material 3.
  7. Click OK to save the material properties and exit the dialog.

4.0 Creating Geometry

The Slope Wizard tool can be used to quickly create a simple extruded slope containing multiple material strata. In this tutorial, the Slope Wizard mainly serves to create the slope cut geometry of the sedimentary formation. The dike will be created in the following section using other geometry tools available in RocSlope3.

4.1 Slope Creation via Slope Wizard

The slope has a dip of 65 degrees and a height of 20 m. The domain of interest runs 200 m into the page (extrusion length).

  1. Select Geometry > Slope Wizard Slope Wizard icon
  2. In the Slope Wizard dialog, enter the following inputs in the Geometry tab.
    1. Set Origin X = 0
    2. Set Origin Y = 0
    3. Set Origin Z = 0
    4. Set Angle θ1 = 65 degrees
    5. Set Angle θ2 = 0 degrees
    6. Set Angle θ3 = 0 degrees
    7. Set Height H1 = 20 m
    8. Set Height H2 = 30 m
    9. Set Length L1 = 30 m
    10. Set Length L2 = 50 m
    11. Set Extrusion Distance = 200 m
    12. Set Extrude Along = Y-Axis.
  3. Inputs for the Slope Wizard dialog.
    Slope Wizard Dialog
  4. Click on the Materials tab. You should find options to create multiple material strata. For this tutorial, leave the fields in the Material tab at their default, so that the simple extruded slope contains only Material 1.
  5. Click OK.

A simple extruded slope geometry has been created and assigned material of Limestone.

Model
3D View of Slope external geometry created from Slope Wizard

4.2 Dike Creation via Geometry Tools

The dike consists of a granite, which is a different material from the sedimentary formation (Limestone) and needs to be created as its own material volume. We will construct 2 planar surfaces depicting the dike interfaces. These planes also serve to divide the sedimentary rock and dike into separate material volumes.

4.2.1 Plane Creation

Create planar surfaces that represent the interfaces between the dike and sedimentary formation.

  1. Geometry > 3D Primitive Geometry > Plane
  2. Expand the Plane Definition section and define the plane as follows:
    1. Plane Definition
      1. Origin (X,Y,Z) = 35,100,25
    2. Plane Orientation
      1. Defined by = Dip/Dip Direction
      2. Dip = 70 degrees
      3. Dip Direction = 70 degrees
      4. Rotation Around Normal = 0
      5. Role = Geology
  3. Inputs for plane geometry definition.
    Create Plane Dialog
  4. Click OK to finish defining the plane and to exit the dialog.

A plane is created.

3D View of Slope and Plane 1
3D View of Slope and Plane 1

Create a second plane by making a copy of the first plane and offsetting it by a distance.

  1. In the Visibility Tree, select Plane 1. This plane should now be highlighted in the 3D views.
  2. Geometry > Copy > Copy (Array) Copy icon
  3. In the Copy Entity dialog:
    1. Copy Mode = 1D-Array Copy
    2. Copies = 1
    3. Spacing = 15
    4. Define by = X-Axis
  4. Inputs for plane copy and offset.
    Inputs for plane copy and offset
  5. Click OK.

The second plane created and offset from the first plane by 15m in the x-axis direction.

3D View of Slope, Plane 1 Original, and Plane 1 Copy 1
3D View of Slope, Plane 1 Original, and Plane 1 Copy 1

4.2.2 Divide Material Volumes

In the Visibility Tree, notice that the Slope volume entity has a lock symbol beside its entry, meaning that it is an “External”. To divide the “External” volume by the planes just created:

  1. Geometry > 3D Boolean > Divide All Geometry divide all icon
  2. Use default parameters in the Divide All Parameters dialog.
    Divide all parameters
  3. Click OK.

After Divide All, there should be 3 slope volume entities, and each is an “External”.

3D View of Slope_1, Slope_2, and Slope_3 external pieces after Divide All
3D View of Slope_1, Slope_2, and Slope_3 external pieces after Divide All

4.3 Material Properties

All volumes have the first material property (Limestone) assigned by default. This material property is appropriate for the sedimentary formation but not the dike.

To change the material property of the dike volume:

  1. Select the dike volume entity (Slope_2) from the Visibility Tree.
  2. In the Properties pane at the bottom left, change the Applied Property to Granite.

The slope model should now appear with Slope_1 and Slope_3 assigned with Limestone material and Slope_2 assigned with Granite material.

Slope geometry with dike.
3D View showing slope geometry with dike

5.0 Add Joints from Surface Geometries

The sedimentary formation is to be populated with a DFN, imported from DFN.dxf file (this is included in the RocSlope3 Tutorials folder). Additional joint surfaces are to be applied to the two dike interfaces.

5.1 Import DFN

  1. Select Geometry > Import/Export > Import Geometry Import geometry icon
  2. Select and open DFN.dxf.
  3. In the Import Geometry dialog, you should see two parallel joint sets. Select “All Geometry” for import.
    Import geometry
  4. Click Post-Processing.
  5. Click Done.

In the Visibility Tree, two new surface entities should have appeared, one for each parallel joint set.

3D View showing the slope and imported surfaces
3D View showing the slope and imported surfaces
Typically, geometry simplification and repair are recommended following geometry import or modification. However, the .dxf has already been cleaned and repaired, so these steps can be skipped for this tutorial.

5.2 Define Joint Properties

The DFN and dike interfaces are still geometry surfaces at this point and need to be converted to joint surfaces with appropriate shear strengths.

To define the joint shear strengths:

  1. Select Joints > Define Joint Properties Define joint properties icon
  2. Add 2 new joint properties (for 3 in total) by clicking the add add icon icon.
  3. For Joint Property 1:
    1. Set Strength Type = Mohr-Coulomb
    2. Set Cohesion 0 MPa.
    3. Set Phi = 30 deg.
    4. Set Override by Material = FALSE.
    5. Set Waviness = 0.
      Joint Property 1
  4. For Joint Property 2:
    1. Set Strength Type = Mohr-Coulomb
    2. Set Cohesion 0 MPa.
    3. Set Phi = 35 deg.
    4. Set Override by Material = FALSE.
    5. Set Waviness = 0.
      Joint Property 2
  5. For Joint Property 3:
    1. Set Strength Type = Mohr-Coulomb
    2. Set Cohesion 0 MPa.
    3. Set Phi = 28 deg.
    4. Set Override by Material = FALSE.
    5. Set Waviness = 0.
      Joint Property 3
  6. Click OK to save the joint properties and to exit the dialog.

Joint Properties 1 and 2 are to be applied to the DFN, whereas Joint Property 3 is to be applied to the dike interfaces.

5.3 Add Joint Surfaces

  1. In the Visibility Tree, select the DFN surface entity with joint dip/dip directions 40 deg/300 deg (DXF clean.Default.Mesh 1).
  2. Select Joints > Add Joint Surface Add joint surface icon.
  3. In the Add Joint Surface dialog, set Joint Property = Joint Property 1.
    Add Joint Surface dialog
    Add Joint Surface Dialog with Joint Property 1 Selected

  4. Click OK.
To assign another surface entity as a joint surface.
  1. In the Visibility Tree, select the DFN surface entity with joint dip/dip direction 70 deg/200 deg (DXF clean.Default.Mesh 2).
  2. Select Joints > Add Joint Surface Add joint surface icon.
  3. In the Add Joint Surface dialog, set Joint Property = Joint Property 2.
    Add joint Surface dialog
    Add Joint Surface Dialog with Joint Property 2 Selected

  4. Click OK.
To assign the dike interfaces as Joint Surfaces:
  1. Expand the dike volume node in the Visibility Tree.
  2. In the expanded tree, hold CTRL for multiple selection and select the two planes (Plane 1 Original and Plane 1 Copy 1) representing the dike interfaces.
    Dike volume node expanded in the visibility tree
    Dike volume node expanded in the visibility tree
  3. Select Joints > Add Joint Surface Add joint surface icon.
  4. In the Add Joint Surface dialog, set Joint Property = Joint Property 3.
    Add Joint Surface dialog
    Add Joint Surface Dialog with Joint Property 3 Selected

  5. Click OK.

The joint surfaces have been added to the model with the appropriate joint properties.

3D View showing the slope and joint surfaces
3D View with slope and joints trimmed to the limestone volume boundaries (no DFN in dike)

5.4 Trim Joints

Trim the joints to restrict the DFN extent to the sedimentary formation (Limestone):

  1. Joints > Trim Joints trim joints icon
  2. In the Select Joints for Trimming dialog, select the joint surfaces that represent the DFN (Joint Surface and Joint Surface 2).
  3. Select joints for trimming.
    Select joints for trimming dialog
  4. Click Next.
  5. In the Select Volumes to Trim Joints dialog, select the volumes with “Limestone” as the assigned material (Slope_1 and Slope_3). The joints will be trimmed to the boundaries of these volumes.
  6. Trim joints to the boundaries of the Limestone volumes.
    Trim joints to the boundaries of the Limestone volumes
  7. Click OK

The slope model should now appear as follows with the selected DFN surfaces cropped within the selected volumes.

Joints trimmed to the limestone volume boundaries (no DFN in dike).
3D View with slope and joints trimmed to the limestone volume boundaries (no DFN in dike)

6.0 Compute

The model is now ready to compute.

  1. Select the Compute workflow tab Compute workflow tab
  2. In the toolbar, click Compute Blocks Compute blocks icon (or select Analysis > Compute Blocks in the menu).
    Compute blocks
    3D View showing All Valid Blocks results after Compute Blocks
  3. Click Compute Kinematics Compute Kinematics icon (or select Analysis > Compute Kinematics in the menu).

7.0 Results

  1. Select the Results workflow tab Results workflow tab
  2. Select Interpret > Contour Blocks contour blocksto view the Factor of Safety of the blocks.
  3. In the Visibility Tree, select the Results node, and ensure the Results Set = All Valid Blocks. This means that you are viewing all valid blocks that formed as a result of joint intersections.
results
3D View of block results contoured by Factor of Safety

Notice that blocks only formed around the dike and not within the dike itself. Also notice that two daylighting and failing blocks are immediately below and adjacent to the dike, where one of the dike interfaces serves as a failure surface.

This concludes Tutorial 9.

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