Pressure

The Pressure option in the Support menu allows you to specify a distributed force that is applied to the slope face and/or the upper face of the wedge. The pressure is specified in terms of force per unit area and may represent:

• Support pressure (for example, rock bolts applied to the slope face of the wedge)
• Loading pressure (for example, a distributed surcharge load on the upper face of the wedge)

The Pressure option is the easiest way to model the effect of pattern bolting or distributed surcharge loads because the user does not have to calculate the total force or define individual bolts (as with the Add Bolt or External Force options). When Pressure is applied, the total force applied to the wedge is automatically calculated by SWedge based on the wedge face area(s) and the pressure magnitude.

To use the Pressure option:

1. Select Pressure on the Support menu.
2. In the Pressure dialog, use the checkboxes to select which face of the wedge you would like to apply the pressure to (the Slope Face or the Upper Face of the wedge, or both).
   By default, the Orientation (Trend and Plunge) of the pressure is Normal to the face of the wedge (i.e., the Slope Face or the Upper Face). However, you may enter any orientation by entering the desired Trend and Plunge. For example, if you are modelling a horizontal rock bolt pattern applied to the Slope Face, enter Plunge = 0).
3. Enter a value for the Pressure (i.e., force per unit area of wedge face).

EXAMPLE: If rock bolts with an individual capacity = 20 tonnes are installed on the Slope Face at a 2 meter by 2-meter spacing, the equivalent support Pressure equals 20 / (2 * 2) = 5 tonnes per square meter. This is the support Pressure to enter in the Pressure dialog.

1. Select either Active or Passive as the Support Model (for details, see How Bolts are Implemented in SWedge.
2. Click Apply to run the analysis without closing the dialog or click OK to run the analysis and close the dialog.
   You should see a change in the Factor of Safety.