Seafloor contact

Settings for sea floor contact and the segments that can be in contact with the sea floor.

  • Specification of the the sea floor contact type, Contact. Components types are:

    • Riser Soil contact

    • Seafloor Spring Contact

  • The seafloor contact is given either for a single segment, all segments in a given line or for all lines in the system (i.e. all segments in the system).

Sea floor contact will be checked for all specified segments. The selected segments should be limited to the ones that can contact the seafloor, see picture below.
This is valid for slender system only.

See theory manual: Contact Formulation

seafloorcontactspecification
Figure 1. Seafloor contact

1. Riser Soil Contact

The contact model includes in addition to the sea floor contact:

  • nonlinear stiffness as the pipe is pressed into the seafloor and a separate unloading curve as the pipe is lifted

  • suction forces are activated as the pipe is lifted off the seafloor

References

Voie, P. E., Skeie, G. and Bergan-Haavik, J. (2014):Importance Rating of Riser-Soil Interaction Effects,OMAE2014

1.1. Sea floor soil properties

Available input parameters are

  • Submerged weight of the soil

  • Soil shear strength at sea bed

  • Soli shear strength vertical gradient

  • Soil Poisson ratio

  • Soil G-modulus/compressive strength

1.2. Normal contact model options

Available input parameters are

  • Relationship between dynamic stiffness and G-modulus

  • Control parameter for suction release displacement

  • Scaling factor for peak soil suction relative to peak soil compression

  • Mobilization displacement for soil bearing capacity as fraction of pipe soil contact width

  • Mobilization displacement for max soil suction as fraction of pipe soil contact width

A set of default values are specified

1.3. Sea floor in-plane contact

For sea floor normal in-plane contact in axial direction the specification consists of

  • Axial stiffness

  • Axial friction

  • Axial damping

For sea floor normal in-plane contact in lateral direction the specification consists of

  • Lateral stiffness

  • Lateral friction

  • Lateral damping

2. Seafloor Spring Contact

The seafloor contact formulation includes

  • contact normal to the seafloor modelled by springs

  • in-plane contact modelled by a combination of springs and frictional forces.

For sea floor normal contact the specification consists of

  • Normal stiffness

  • Normal damping

For sea floor normal in-plane contact in axial direction the specification consists of

  • Axial stiffness

  • Axial friction

  • Axial damping

For sea floor normal in-plane contact in lateral direction the specification consists of

  • Lateral stiffness

  • Lateral friction

  • Lateral damping


  • As default, the lateral contact forces (spring or friction forces) are applied at the centerline of the element. Optionally, the lateral forces mat be applied at the external contact radius, thus also also applying a torsional load contribution.