Datum - The pre-mining stress state is specified as a linear variation with depth in either principal or Cartesian components.
Copy from... - allows you to copy the stress state from another material.
•Only the stress state is copied.
•Other material properties are left unchanged.
Cartesian - The pre-mining stress state is specified as a linear variation with depth in either principal or Cartesian components.
The three principal stress components are referred to as the Hmax, Hmin and Vert components.
•σHmax is the maximum (nearly) horizontal stress.
•σHmin is the minimum (nearly) horizontal stress.
•σVert is the (nearly) vertical stress.
These stress components are perpendicular to one another.
The horizontal and vertical components do not need to be exactly horizontal or vertical.
The trend and plunge of σHmax can be adjusted using THmax and PHmax.
The trend of σVert can be adjusted using TVert.
The variation of each of these components is described as a linear variation with depth as (for example for the σHmax component)
σHmax + ΔσHmax (z - Datum)
To determine appropriate values for each of these components the user must first select a depth z where the stresses have known values.
Datum should be set to this z value.
The magnitude of the stress at this depth is specified by the following constant values
σHmax σHmin σVert
The variation of each component with depth can then be specified by the following variation values
ΔσHmax ΔσHmin ΔσVert
If you have set up your coordinate system with z positive up, then the variations should be specified as negative quantities so that the stresses increase with depth.
For example if you know that the Hmax component has a value of
30 MPa at z = 1000m
and varies as (z is positive up)
0.027 MPa/m
you would specify
Datum = 1000
σa = 30
Δσa = -0.027
Finally, the trend and plunge of the Hmax component and the trend of the Vert component uniquely define the stress state orientation.
The parameters
t/h constant
Δt/h variation
refer to the ambient temperature/head distribution and are specified in the same manner as the stresses.