Design Factor of Safety

A Design Factor of Safety can be specified in the Input Data dialog under the General tab.

The Design Factor of Safety is the minimum factor of safety required for the excavation (i.e. all wedges should have a Factor of Safety greater than or equal to the Design Factor of Safety).

In Unwedge, the Design Factor of Safety is only used for the following purposes:

Wedge Visibility Filtering

For the Wedge Visibility option (available in the Sidebar for the 3D Wedge View and the Perimeter Support View), in the drop down list you will notice the "FOS < Required" option. The "Required" Factor of Safety is the Design Factor of Safety. If you select this option, only wedges with a Factor of Safety less than the Design Factor of Safety will be displayed.

Support Pressure Requirement

For the Tunnel Axis plots, in the drop down list of Data to Plot you will notice the "Pressure for FS=###" option. The Factor of Safety is the Design Factor of Safety. This option allows you to determine the required support pressure necessary to achieve the Design Factor of Safety (for the wedge with the lowest unsupported safety factor). For more information see the Tunnel Axis Plot topic.

NOTE !!! It is important to understand that the Design Factor of Safety entered in the Input Data dialog, has no effect on the results of the Unwedge analysis. The Design Factor of Safety is NOT used in any way during the safety factor calculations for the wedges. It is ONLY used for the purposes described above.