Tension Crack

A Tension Crack can be included in the Swedge analysis, by selecting the Tension Crack checkbox in the Input Data dialog, and defining the Tension Crack orientation and location, as described below. NOTE:

• A Tension Crack is optional in the Swedge analysis. By default, Swedge does NOT consider a Tension Crack in the analysis.

• By definition, a Tension Crack in Swedge has ZERO shear strength. It does NOT contribute to the forces resisting wedge movement. It simply truncates the size of the wedge.

• However, if Water Pressure is included in the analysis, the resultant force will be applied to the Tension Crack plane, if applicable.

Definition of Tension Crack for Swedge analysis (plane # 5)

Tension Crack Orientation

The Tension Crack orientation is defined by entering the Dip and Dip Direction of the Tension Crack plane in the Input Data dialog. NOTE:

• The Tension Crack does NOT have to be vertical. Swedge allows you to enter any orientation for the Tension Crack plane.

• However, if a Tension Crack is defined, Swedge examines how the Tension Crack intersects the other planes, and only accepts those cases where the Tension Crack truncates the wedge in the manner shown in the figure above.

• If the Tension Crack plane does not form an acceptable wedge with the other planes, Swedge will report "No Wedge Formed".

• A Tension Crack is not "interchangeable" with a joint plane in the Swedge analysis (i.e. it will not be considered as a joint plane, regardless of the Tension Crack orientation).

• In a Probabilistic Analysis, you can define statistical variability of the Tension Crack orientation.

Tension Crack Location

In the Input Data dialog, there are THREE possible methods of defining the location of the Tension Crack. These options are described below.

Minimum FS Location

If this option is selected, then Swedge will automatically determine the location of the Tension Crack which results in the MINIMUM factor of safety for the wedge.

Specify Location

If this option is selected, then the location of the Tension Crack can be user-defined by entering a Trace Length with respect to Joint 1. The Trace Length is the distance of the Tension Crack from the crest, measured along the trace of Joint 1 on the Upper Slope Face. See the above figure. Length L is the trace length used to specify the Tension Crack location.

Use Bench Width to Maximize

NOTE: this option is only available if the Bench Analysis checkbox is selected in the Input Data dialog.

If this option is selected, then Swedge will automatically locate the Tension Crack to create the maximum possible wedge size for the specified Bench Width. This is illustrated in the following figure.

Tension Crack location determined by Bench Width

NOTE: if you use this option, it is possible that no Tension Crack will be formed. This depends on the value of the Bench Width.