Add Surface

If the Surface Type = Circular in the Surface Options dialog, the Add Surface options in the Surfaces menu allow you to define specific CIRCULAR slip surfaces. There are two different options for defining a specific CIRCULAR slip surface:

• Add Surface (center, radius)
• Add Surface (three points)

Add Surface (center, radius)

The Add Surface (center, radius) option, allows you to define a specific circular failure surface by entering a center and radius. To use this option:

1. Make sure the Surface Type = Circular in the Surface Options dialog.
2. Select Add Surface (center, radius) from the toolbar or the Surfaces menu.
3. You will first be prompted to enter the center of rotation of the circular slip surface. Use the mouse to graphically select a point, or enter the x,y coordinates in the prompt line.
4. You will then be prompted to enter the circle radius. As you move the mouse, you will see a circle drawn on the screen, and the numerical value of the current radius will be displayed on the prompt bar, at the bottom left of the application window. You can graphically enter the radius by dragging the circle to the desired radius and clicking the mouse. Or you can enter a radius in the prompt line.
5. After the radius has been entered, the slip surface will be added to the model.

Add Surface (three points)

The Add Surface (three points) option, allows you to define a specific circular failure surface by entering any three points on the slip surface. Remember that 3 unique points are necessary and sufficient to define a circle, as long as they are not on the same straight line. To use this option:

1. Make sure the Surface Type = Circular in the Surface Options dialog.
2. Select Add Surface (three points) from the toolbar or the Surfaces menu.
3. Enter the first point, graphically with the mouse, or enter coordinates in the prompt line with the keyboard.
As you move the mouse, a small red cross follows the cursor location. This cross will "snap" to the nearest boundary if you are close to the boundary. You can use this to graphically "snap" the point exactly on a boundary.
4. Enter the second point, as described above.
5. After the second point is entered, as you move the mouse, a circle will automatically be drawn on the screen, connecting the first two points to the current cursor location. You can use this as a guide for entering the third point which defines the circle.
6. Enter the third point, and the slip circle will be added to the model.

Tips

• Any number of specific circular surfaces may be defined for a model.
• Specific circular surfaces and a circular surface search, can be defined for the same analysis. i.e. you may analyze specific surfaces, and perform a critical surface search at the same time on the same model, this does not cause any problems.
• Specific circular surfaces created using the Add Surface options, can be deleted using the Delete Surfaces option. Delete is also available as a right-click shortcut. When selecting a specific circular surface to delete, you may select EITHER the center point or the slip surface.