The on-bottom stability assessment can be based on either The DNV RP F109’s generalised or absolute stability methodology. The generalised stability method is based on allowable displacement in a design spectrum of oscillatory wave induced velocities perpendicular the pipeline at the pipeline level. The generalised method is based on DNV’s own database of large number of one dimensional dynamic analyses on flat seabed. The generalised method provides required minimum concrete coating for lateral stability with an allowed lateral displacement, i.e allowable lateral displacement of 0.5D to 10D. The absolute lateral stability method is a “design wave” approach where static equilibrium of forces is obtained, the resistance of the pipe against motion is sufficient to withstand maximum hydrodynamic loads during a sea state (i.e the pipeline will experience no lateral displacement under the design extreme single wave and current induced oscillatory cycle in the sea state considered).
Reference :
DNV RP F109
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