Tunnel Orientation

The Tunnel Orientation is a required input parameter (entered in the Sidebar), if you are using the Complete Plane Strain Analysis Type (selected in Project Settings).

Complete Plane Strain allows you to define a three-dimensional, arbitrarily oriented in-situ Field Stress, with respect to the excavation axis. Therefore you must define the orientation of the excavation axis (Tunnel Orientation), if you are using Complete Plane Strain.

• If the Field Stress Type = Constant, then you must define BOTH the Trend and Plunge of the excavation axis.

• If the Field Stress Type = Gravitational, then you must define the Trend of the excavation axis. Plunge is automatically set to zero, because the Gravitational field stress option assumes that the excavation axis is horizontal.

Tunnel Orientation input for Constant field stress

Summary of Tunnel Orientation input requirements

Note:

• The "Tunnel Orientation" refers to the out-of-plane axis of your excavation model. The excavation does not necessarily have to represent a tunnel (e.g. it could be a vertical shaft or other linear excavation with arbitrary orientation).

• If the Analysis Type = Plane Strain, then the Tunnel Orientation is not required, since the excavation axis is by definition, parallel to the out-of-plane Field Stress.