Constant Field Stress

Use the Constant Field Stress option if you wish to specify an initial in-situ stress field (prior to excavation) which is constant, and does not vary with depth. Only the direction and magnitude of the principal stresses need to be defined.

• See the Field Stress topic for general information about using the Field Stress option in UnWedge.

Principal Stress Magnitudes

Sigma 1, Sigma 2, and Sigma 3 are the major, intermediate and minor principal stresses respectively.

By definition:

• The Magnitude of Sigma 1 >= Sigma 2 >= Sigma 3
• If Sigma 1 = Sigma 3 then this represents hydrostatic stress conditions (equal stress in all directions)

Principal Stress Orientation

By definition:

• The orientations of Sigma 1, 2, 3 are orthogonal to each other, therefore the Trend / Plunge of Sigma 1 and Sigma 3 must be defined accordingly.
• The orientation of Sigma 2 cannot be independently specified because Sigma 2 is orthogonal to BOTH Sigma 1 and Sigma 3.