The Tunnel Axis Orientation is the Trend / Plunge of the excavation axis, looking "down" the axis of the excavation or tunnel.
The Tunnel Axis Orientation may be entered in:
the General tab of the Input Data dialog
the Sidebar for most of the Unwedge Views (e.g. Opening Section View, 3D Wedge View etc)
in the Tunnel Axis Plot view, the Tunnel Axis Orientation can be graphically and interactively modified, using the contours as a guide.
For horizontal excavations the Plunge = 0, and remember that the Trend assumes that the viewer is "facing" the Opening Section cross-section, looking along the excavation axis.
For inclined (e.g. ramp) or vertical excavations, remember that the Trend must correspond to the Y-axis of the Opening Section as defined in the Opening Section view. For vertical excavations the Plunge = 90.
The Tunnel Axis Orientation can be optimized with respect to any analysis output variable, for example: maximum wedge volume, minimum factor of safety, minimum support pressure to achieve design factor of safety etc. This can be done with a single mouse click -- see the Tunnel Axis Plot topic for details.