OGS

This class defines a linear saturation rate dependent swelling stress model for the materials that swell strongly when water content increases.
Clay materials like bentonite have a high swelling capacity in dry state, and their swelling property can be described by this model.
The original model was proposed in [34] (equations (39) and (40) on pages 758–759). With a simplification of the parameters of the original formula and introducing a constraint to avoid shrinkage stress when saturation is below the initial saturation, the model takes the form
\[ {\mathbf{\sigma}}^{\text{sw}} = {\alpha}_{\text{sw}} (SS_0) \mathbf{I}, \, \forall S \in [S_0, S_\text{max}] \]
where \({\alpha}_{\text{sw}}\) is a coefficient, and \(S_0\) is the initial saturation, and \(S_{\text{max}}\) is the maximum saturation. The coefficient gives the swelling stress at full saturation, which can be computed as
\[ {\alpha}_{\text{sw}} = \frac{{{\sigma}}^{\text{sw}}_{\text{max}}}{(S_{\text{max}}S_0)} \]
where \({{\sigma}}^{\text{sw}}_{\text{max}}\) represents the swelling stress at full saturation.
In the numerical analysis, the stress always takes the incremental form. Therefore the model becomes as
\[\Delta {\mathbf{\sigma}}^{\text{sw}} = {\alpha}_{\text{sw}} \Delta S \mathbf{I}, \, \forall S \in [S_0, S_\text{max}] \]
Note:
No additional info.
Used in no endtoend test cases.