Opening Section Coordinates

When you define the Opening Section boundary, a local X-Y coordinate system is used, where:

Opening Section Orientation

The relationship of the Opening Section X-Y coordinate system to the 3-dimensional orientation of the excavation you are modeling, is as follows:

Horizontal Excavations

If your Tunnel Axis Orientation is horizontal (i.e. Plunge = 0 degrees), then the positive Y-axis of the Opening Section boundary corresponds to the Global Vertical Up direction.

Inclined or Vertical Excavations

If your Tunnel Axis Orientation is non-horizontal (i.e. Plunge > 0), then the positive Y-axis of the Opening Section boundary must correspond to the Trend of the Tunnel Axis Orientation.

Note: this is also true for vertical excavations (Plunge = 90 degrees)

In all cases, the X-axis of the Opening Section boundary is perpendicular to the Tunnel Axis Orientation.

Coordinate Values

The absolute values of the X-Y coordinates which you use to define the Opening Section boundary, is not important, except for the following cases:

Except for these cases, you may define the Opening Section boundary coordinates anywhere in the X-Y plane, and this will not affect the results of the Unwedge analysis.