Data part, material properties

The material properties for the soil are the same as in tutorial 3.

For the sheet pile we will use isoparametric quad4 elements with a large fictive thickness. As density we simply take the soil density, we is OK since most of the fictive thickness in reality will actually consist of soil. The young modulus we fitted in such way that the bending behavior of the isoparametric quad4 elements is the same as that of the truss_beam elements of tutorial 3 (in fact, we have simply put a force at the bottom of the quad4 elements and truss_beam elements, and tuned the young modulus of the quad4 elements such that the same displacement was obtained with both models).

start_define
sheet_pile_group 2
end_define
group_type sheet_pile_group -materi
group_materi_memory sheet_pile_group -total_linear
group_materi_density sheet_pile_group 1.702
group_materi_elasti_young sheet_pile_group 5.9874e6

For the slip between soil and sheet pile we will use interface elements. The stiffness of interface elements should be taken high enough, so that the deformations in the interface elements are relatively small. On the other hand, the stiffness of interface elements should not be too large, because that would lead to a bad conditioned matrix and numerical problems. The interfaces are not allowed to transfer tension stresses, and slip frictional forces are restricted by a Mohr-Coulomb law; the friction angle of the Mohr-Coulomb law is taken such that ${\rm tan}(phi_{\rm interface}) = 0.5 * {\rm tan}(phi_{\rm soil})$.

start_define
interface_group 3
end_define
group_type interface_group -materi
group_interface interface_group -yes
group_interface_materi_memory interface_group -total_linear
group_interface_materi_elasti_stiffness interface_group 10.e10 5.e10
group_interface_materi_plasti_mohr_coul_direct interface_group 0.4636 1. 0.
group_interface_materi_plasti_tension interface_group -no

For convergence of the calculation, it is required to use a quite small interface stiffness.