Define Slope Limits

You can customize the Slope Limits at any time with the Define Limits or Move Limits options. Changing the Slope Limits allows you to narrow or modify the allowable locations of slip surfaces, when a slip surface search is being performed. For a definition of the Slope Limits in Slide see the Overview of Slope Limits topic.

NOTE: the Move Limits option allows you to change the Slope Limits graphically, with the mouse. The Define Limits option allows you to enter exact numbers in a dialog, as described below.

To change the Slope Limits with the Define Limits option:

  1. Select Define Limits from the toolbar or the Slope Limits sub-menu of the Surfaces menu. You will see the Define Slope Limits dialog.

  2. Enter new values for the Left and / or Right Limits, and select OK.

  3. The triangular Slope Limit markers will indicate the new locations of the Slope Limits on the External Boundary.

Defining two sets of Slope Limits

Two sets of Slope Limits can be defined, if you want to define allowable ranges for the starting and ending points of the slip surfaces. To define two sets of Limits:

  1. In the Define Slope Limits dialog, select the Second set of limits checkbox.

  2. You can now enter Left and Right limits for two sets of Slope Limits. Enter the values, and select OK.

  3. On the External Boundary, you will now see FOUR triangular Slope Limit markers, showing the location of the Left and Right Slope Limits for the two ranges you have entered.

If you run an analysis using two sets of Slope Limits, you will see that all slip surfaces intersect the External Boundary ONLY within the limits you have defined.

Slope Limits on Vertical Boundaries

In the Define Slope Limits dialog, the position of the Slope Limits is specified by X-coordinates only. However, it is sometimes necessary to specify the position of a Slope Limit on a VERTICAL boundary.

Since only X-coordinates are allowed in the Define Slope Limits dialog, vertical positioning CANNOT be specified in the dialog. As indicated in the text note in the dialog, if you need to position a Slope Limit on a vertical boundary, you must do this graphically, with the Move Limits option.

Slope Limits on vertical boundaries are sometimes required when a vertical slope face is being modeled, for example. Depending on how you have defined the External Boundary, a default slope limit calculated by Slide may appear at the top of a vertical slope face. If this occurs, and you need to position a Slope Limit at the bottom of the vertical slope face, you must do this graphically with the Move Limits option.

Resetting the Default Limits

To reset the default Slope Limits which are automatically calculated by Slide when the External Boundary is created or modified, you can select the Reset button in the Define Slope Limits dialog. You can also use the Reset to Default option in the Slope Limits sub-menu of the Surfaces menu.

Right Click Shortcut

If you right click on any Slope Limits marker, a popup menu will appear, with shortcuts to the Define Limits, Move Limits and Reset options. You may find this a useful shortcut for modifying or resetting the slope limits.