A strain dependent bimodal water retention model.

It is based on the van Genuchten model.

The equation is as follows

$S_{e} = \left((e_{m}+a \Delta e) \left[\frac{1}{((\frac{p_{c}}{p_{b}})^{n}+1)}\right]^{m} + (e_{M} - a \Delta e) \left[\frac{1}{((\frac{p_{c}}{p_{{b,M}}})^{n} +1)}\right]^{n} \right) \frac{1}{e}$

with effective saturation defined as $S_{e}=\frac{S-S_r}{S_{max}-S_r}$ , where $S_r$ and $S_{max}$ are the residual saturation and the maximum saturation, respectively. The exponent $m \in (0,1)$ is the same as in the van Genuchten equation ( see SaturationVanGenuchten). In the original work another exponent $n$ is used, but usually set to $n = 1 / (1 - m)$ , and also in this implementation. The pressure scaling parameter $p_{b}$ is added by the user and is the scaling parameter of the micropores. The scaling parameter of the macropores can be calculated as follows $p_{b,M} = p_{b} d_{diff}$ The total void ratio and the void ratio of the micropores are $e_0$ and $e_m$ . Another scaling factor $a$ scales the effect of the strain

The changing void ratio is calculated as $\Delta e = -\frac{(1-e)\epsilon_{vol}}{e}$ , with $\epsilon_{vol}$ as the volumetric strain. The result is then clamped between the residual and maximum liquid saturations.

Child parameters, attributes and cases

Additional info

Used in the following test data files