The Add Axis option allows you to define a single axis point, which will be used for moment equilibrium calculations, for ALL surfaces generated by a non-circular surface search (e.g. Block Search or Path Search).
To add an axis point:
Select Add Axis from the toolbar or the Surfaces menu.
Enter the axis point graphically with the mouse, or by entering the x,y coordinates of the axis point in the prompt line, and pressing Enter. The axis point should of course be entered somewhere above the slope. As a general guideline, the axis point should be located at APPROXIMATELY the center of rotation of the non-circular slip surfaces (i.e. estimate a best fit circle which passes through the area of the Block Search or Path Search, and use the center of this circle as the axis point).
The axis point will be displayed, and you will exit the Add Axis option.
Only ONE axis point can be defined for a model.
It is important to note that the Add Axis option is entirely optional. It is NOT necessary for the user to define an axis point, since Slide automatically calculates an axis point for EACH non-circular slip surface generated by a Block Search or a Path Search.
If an axis point IS DEFINED by the user with the Add Axis option, then this point will be used for the moment equilibrium calculations, for ALL surfaces generated by the non-circular surface search. In this case, Slide will NOT automatically calculate axis points for each non-circular slip surface, since the user-defined axis point will be used for ALL surfaces.
Therefore, only use the Add Axis option if you want a specific point to be used for moment equilibrium calculations for ALL non-circular surfaces generated by a non-circular surface search.