# Soil Material Curves
The value of stiffness (Young's modulus or E) with depth is specified in the soil profiles. For linear materials each specified value of E will remain constant, at the given depth, throughout the calculation for stress, strain and thereby displacement.
For models of materials where the relationship between stress and strain is non-linear a non-linear curve must also be specified.
# Definition
Name
This is only used as a way to easily identify the soil curve.
Stiffness strain curve
The nonlinear soil curve is specified as a factor on the stiffness (Young’s modulus). This can be defined by the specification of a curve of strain versus stiffness factor. The secant stiffness at a particular strain is then the specified E value × factor.