In the Define Material Properties dialog, the Datum Dependent option allows you to define material properties which vary linearly with depth from a user-defined datum elevation. The following properties can be specified as Datum Dependent:
Young's Modulus (only if the material Elastic Type = Isotropic)
Cohesion and Friction Angle (only if Failure Criterion = Mohr-Coulomb and Material Type = Plastic).
To define Datum Dependent properties for a material:
Select the Datum Dependent checkbox in the Define Material Properties dialog.
Select the Define Properties button, and you will see the Datum Dependent Properties dialog, in which you can define the datum dependent properties, as described below.
Young's Modulus
To define Young's Modulus as a Datum Dependent property, select the Young's Modulus checkbox in the Datum Dependent Properties dialog, and enter the following parameters.
Modulus at Datum
The value of Young's Modulus at the Datum elevation. This is the value of Young's Modulus entered in the Define Material Properties dialog. It cannot be edited in the Datum Dependent Properties dialog.
Datum
The datum elevation (y-coordinate).
Change
The rate of change of Young's Modulus with (vertical) distance from the Datum.
Cutoff
If you wish to specify a maximum value of Young's Modulus, select the Cutoff checkbox and enter a maximum value. NOTE: if the rate of Change is negative, then the Cutoff value represents the minimum Young's Modulus.
Cohesion
Cohesion can only be defined as a Datum Dependent property for materials with Failure Criterion = Mohr-Coulomb and Material Type = Plastic.
To define Cohesion as a Datum Dependent property, select the Cohesion checkbox in the Datum Dependent Properties dialog, and enter the following parameters.
Cohesion at Datum (peak)
The value of Cohesion (peak) at the Datum elevation. This is the value of Cohesion (peak) entered in the Define Material Properties dialog. It cannot be edited in the Datum Dependent Properties dialog.
Cohesion at Datum (residual)
The value of Cohesion (residual) at the Datum elevation. This is the value of Cohesion (residual) entered in the Define Material Properties dialog. It cannot be edited in the Datum Dependent Properties dialog.
Datum
The datum elevation (y-coordinate).
Change (peak)
The rate of change of Cohesion (peak) with (vertical) distance from the Datum.
Cutoff (peak)
If you wish to specify a maximum value of Cohesion (peak), select the Cutoff (peak) checkbox and enter a maximum value. NOTE: if the rate of Change is negative, then the Cutoff value represents the minimum Cohesion (peak).
Change (residual)
The rate of change of Cohesion (residual) with (vertical) distance from the Datum.
Cutoff (residual)
If you wish to specify a maximum value of Cohesion (residual), select the Cutoff (residual) checkbox and enter a maximum value. NOTE: if the rate of Change is negative, then the Cutoff value represents the minimum Cohesion (residual).
Friction Angle
Friction Angle can only be defined as a Datum Dependent property for materials with Failure Criterion = Mohr-Coulomb and Material Type = Plastic.
To define Friction Angle as a Datum Dependent property, select the Friction Angle checkbox in the Datum Dependent Properties dialog, and enter the Datum Dependent Friction Angle variables.
The definitions of the Datum Dependent variables for Friction Angle are the same as the definitions for Cohesion - see above for details.