is available in the toolbar, the View menu, and also in the
right-click menu (if you right-click the mouse anywhere in the Failure
Envelope display area).The appearance of the Failure Envelope Plots may be customized with Display Options, zooming, and other options.
Display Options is available in the toolbar, the View menu, and also in the
right-click menu (if you right-click the mouse anywhere in the Failure
Envelope display area).
Most of the display and zoom options are self-explanatory, and it is left to the user to experiment with the options. However, we will note the purpose of the following options:
Mogi’s Line
Mogi’s Line defines the ratio of major and minor effective principal stresses at which there is a transition from brittle to ductile failure. This line is defined by sig1/sig3 = 3.4, and is plotted as a green line on the principal stress plot, when the Mogi’s Line option is selected in the Display Options dialog.
If the principal stress failure envelope lies ABOVE Mogi’s line, this indicates a brittle failure mode.
If the principal stress failure envelope lies BELOW Mogi’s line, this indicates a ductile failure mode. This may occur with low values of GSI, for example.
Display of Mogi's Line
Graph Icons
The Graph Icons represent the principal stress and shear-normal stress plots, and help you to quickly identify the type of graph you are viewing. The display of the Graph Icons can be turned on or off in the Display Options dialog.
Principal stress and shear-normal stress graph icons
By default, the Graph Icons are displayed at the lower right corner of the failure envelope plots.
TIP: the Graph Icons can be moved to a different location by clicking on them with the mouse and dragging them to the desired location in the view.
Zoom Extents
The Zoom Extents option will automatically scale the axes of the failure envelopes for the Generalized Hoek-Brown criterion, so that all possible failure envelopes, for the current value of sigci, will be visible on the plot.
This corresponds to maximum values of GSI (= 100) and mi ( = 50).
To demonstrate this, select the Zoom Extents option.
Use the interactive arrow 
buttons
to increase the value of GSI to 100, and the value of mi to 50.
Observe the failure envelope plots. When GSI = 100 and mi = 50, the extent of the principal stress envelope will correspond to the maximum extent automatically calculated by the Zoom Extents option.
You may find the Zoom Extents option useful for interactive demonstration of parameter changes on the failure envelope.
Grayscale
The Grayscale 
option, available in the toolbar or the View
menu, will convert all colours in the plot display area to black and white.
You may find this useful for black and white screen captures or printouts.