Interactive help on using the xMat

Defined in publication from Kolymbas (2021) with more details in Kolymbas (2022)
Expects the following ten material parameters:
- 1: $\varphi_c$ (rad),
- 2: $c_2$ ,
- 3: $c_3$ ,
- 4: $c_4$ ,
- 5: $c_5$ ,
- 6: $\kappa_1$ ,
- 7: $\kappa_2$ ,
- 8: $k_1$ ,
- 9: $k_2$ and
- 10: $e_{c0}$
Uses thirteen state variables:
- 1: void ratio,
- 2: first part of the critical void ratio $e_{c1}$ and
- 3: second part of the critical void ratio $e_{c2}$
- 4-12: direction of the strain rate $\vec{D}_{11}$ , $\vec{D}_{22}$ , $\vec{D}_{33}$ , $\vec{D}_{12}$ , $\vec{D}_{21}$ , $\vec{D}_{23}$ , $\vec{D}_{32}$ , $\vec{D}_{13}$ and $\vec{D}_{31}$
- 13: replacement stiffness
Void ratio and first part of the critical void ratio have to be initialized as state variables.