The Seabed component is used to specify the seabed characteristics at a particular location, including seabed profile and longitudinal / transverse friction coefficients. Rigid and elastic formulations are provided, and the profile may be flat, sloping or arbitrarily defined.
The figure above shows the Seabed component view. The Model component requires the specification of a Seabed component. When you are specifying a seabed for a particular model, you select the relevant Seabed from a list of all of the Seabed components that are currently defined in the project. Flat, sloping and arbitrary bathymetry options are provided. Pipelay models a sloping seabed as passing through the global origin and sloping uniformly in the global-XY plane. In other words, the seabed elevation does not vary in the global-Z direction. The angle of seabed slope is measured anti-clockwise from the global-Y axis so that a positive seabed slope means that the seabed elevation increases with increasing distance along the global-Y axis.
To define an arbitrary seabed, you define pairs of points representing a distance along the global-Y axis and the seabed elevation at that point. Again the bathymetry is defined in the XY plane only and is assumed to extend indefinitely in the global-Z direction. You do not actually specify the bathymetry data pairs directly via the PipeLay GUI. Instead the data is input in an ASCII file in a simple pre-defined format, and the file name becomes the GUI input. Using this method of input, the same specification can be used repeatedly, without the necessity for typing the same values into the GUI again and again.
The two seabed formulations are described in the following articles:
•‘Rigid Surface’ provides a list of all relevant inputs for a seabed specified using the rigid surface option.
•‘Elastic Surface’ provides a list of all relevant inputs for an elastic seabed. PipeLay provides both linear and non-linear elastic seabed options.