# 5 - Slope Roughness

## 1.0 Introduction

In this tutorial we will demonstrate the **Slope Roughness** option for **Rigid Body** analysis in **RocFall2**. The Slope Roughness option allows you to generate physical geometric roughness along selected slope segments by defining spacing and amplitude statistical distributions for selected materials.

**Topics Covered in this Tutorial:**

- Rigid Body analysis
- Slope Roughness
- Endpoint graphs

**Finished Product:**

The finished product of this tutorial can be found in the *Tutorial 05 Slope Roughness* data file. All tutorial files installed with RocFall2 can be accessed by selecting **File > Recent Folders > Tutorials Folder** from the **RocFall2** main menu.

## 2.0 Model (NO Slope Roughness)

Let's start by opening the file for the tutorial:

- Select
**File > Recent Folders > Tutorials Folder**and open the*Tutorial 05 initial file*. You should see the following model.

All slope and rock properties have already been defined.

- The Rigid Body rock shape is a 1000 kg sphere
- Number of Rocks = 50
- Slope Roughness is NOT enabled
- Initial Horizontal Velocity = 1.5 m/s
- Distribution = Normal
- Std. Dev = 0.15 m/s
- Rel. Min = 0.45 m/s
- Rel. Max = 0.45 m/s

## 3.0 Results (NO Slope Roughness)

Now we'll compute to run the analysis and see results without any Slope Roughness assigned.

- Select the
**Compute**button from the toolbar or the**Analysis**menu.

### 3.1 GRAPH ENDPOINTS

Next we'll generate an Endpoints graph of results.

- Select
**Graph Endpoints****Graphs**menu. The**Graph Endpoints**dialog should appear. - Set
**Data = Endpoint Location**. - Set
**Value = Number of Rocks**. - Set
**Number of Bins = 50**. - Set
**Paths to Plot = All Rock Paths**. - Select
**Plot Data**to generate the Distribution of Rock Path End Locations graph. - Right-click on the graph and click
**Toggle End Reasons**.

You should see the following graph.

As you can see, most of the rocks have simply reached the end of the model without stopping. These are paths are indicated by "Edge Model".

## 4.0 Slope Roughness

We’ll now look at how adding **Slope Roughness** will affect the results. Slope Roughness is added using the **Slope Material Library**.

- Select:
**Slope > Slope Material Library** - Switch back to
**Design**mode. - Select
**Slope Material Library**on the toolbar or the**Slope**menu. - Select the
**Type Two**material. - Select the
**Slope Roughness**check box. - Keep
**Spacing = 0.20 m.**- Distribution = None

- Keep
**Amplitude =****0.00 m**- Distribution = Normal
- Std. Dev = 0.2 m
- Rel. Min = 0.6 m
- Rel. Max = 0.6 m

- Follow the same steps for material
**Type Three**. - Select
**OK**.

## 5.0 Results (Slope Roughness)

Now we'll **Compute** and view results with Slope Roughness added. You should note that the rockfall paths differ significantly from the model with no Slope Roughness.

Next we'll generate an Endpoints graph to compare it with the one we generated above with no **Slope Roughness**.

- Select
**Graph Endpoints****Graphs**menu. The**Graph Endpoints**dialog should appear. - Set
**Data = Endpoint Location**. - Set
**Value = Number of Rocks**. - Set
**Number of Bins = 50**. - Set
**Paths to Plot = All Rock Paths**. - Select
**Plot Data**to generate the Distribution of Rock Path End Locations graph. - Right-click on the graph and click
**Toggle End Reasons**.

You should see the following graph.

The rock endpoint graph is very different compared to the model with no **Slope Roughness**. Many rocks have come to rest on the upper bench and bottom of the slope, although some still reach the end of the model.

### 5.1 ANIMATE PATHS

Now we'll use the **Animate Path** option to view the rock fall.

- Select
**Animate Path**on the toolbar or the**Results**menu and zoom in if necessary. - In the
**Animate Result**dialog, click through each rock path using the forward arrow beside the rock ID number.

#### NOTES:

- Notice that, each time you view a new rock path, you can see the actual
**Slope Roughness**generated for each rock throw. The Slope Roughness is randomly generated according to the**Spacing**and**Amplitude**statistics you defined above. - As you view the different rock paths, notice the actual Slope Roughness generated for the
**Type Two**and**Type Three**material segments. For the spacing and amplitude values we have entered, the physical roughness is very jagged and not very realistic for an actual slope surface.

## 6.0 Modify Slope Roughness Parameters

Let’s modify the **Slope Roughness** parameters and re-run the analysis to achieve a more realistic modeling of the surface roughness.

- Switch back to
**Design**mode. - Select
**Slope Material Library**on the toolbar or the**Slope**menu. - Select the
**Type Two**material. - Set
**Spacing = 0.5 m**and**Distribution = None**. - Change
**Std. Dev:**for**Amplitude**=**0.1 m**. - Select the
**Type Three**material and repeat the steps above. - Click
**OK**.

## 7.0 Results (Modified Slope Roughness Parameters)

Now we'll **Compute** and view results with Slope Roughness parameters modified.

The rock paths look similar to the previous model. Let’s now generate an Endpoints graph for further comparison.

- Select
**Graph Endpoints****Graphs**menu. The**Graph Endpoints**dialog should appear. - Set
**Data = Endpoint Location**. - Set
**Value = Number of Rocks**. - Set
**Number of Bins = 50**. - Set
**Paths to Plot = All Rock Paths**. - Select
**Plot Data**to generate the Distribution of Rock Path End Locations graph. - Right-click on the graph and click
**Toggle End Reasons**.

You should see the following graph.

#### NOTE:

Compare the distribution of endpoints to the previous model and compare the End Reasons. With the reduced **Slope Roughness**, a greater proportion of rocks have stopped, fewer rocks have wedged, and we have eliminated the Chattering End Reason, which is a numerical issue where rocks have essentially stopped but continue to move slightly and must be arbitrarily stopped. It is preferable that Chattering be avoided, if possible.

### 7.1 ANIMATE PATHS

Now we'll use the **Animate Path** option to view the rock fall.

- Select
**Animate Path**on the toolbar or the**Results**menu and zoom in if necessary. - In the
**Animate Result**dialog, click through each rock path using the forward arrow beside the rock ID number. - Observe the slope roughness generated with the new spacing and amplitude parameters for each rock path.

#### NOTES:

- In general, the modified
**Slope Roughness**parameters (increased**Spacing**and decreased**Amplitude**variability) give a more realistic slope surface roughness. - To achieve a realistic surface roughness, it is recommended that you always experiment with the
**Spacing**and**Amplitude**parameters, and observe the generated surfaces in order to simulate the actual field conditions as closely as possible.

This concludes the tutorial. You are now ready for the next tutorial, Tutorial 06 - Crest Loss in RocFall2.