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# Offshore Pipeline On-bottom stability analysis (On seabed)

## Offshore Pipeline On-bottom stability analysis (On seabed)

(OP)
Dear all,

I have an urgent question (the report posting date comes soon)

Actually I have to study the pipeline On-bottom stability in shallow water area where in almost all cases only the Cnoidal wave theory could be performed. I have noticed that the DNV-RP-f109 and e305 considers only the linear (airy) wave theory and consequently all the parameters used are calibrated considering the airy theory:

- Please could you tell me which parameters I need to change (Cd,Cl etc) from the DNV-RP-f109 in order to have coherent results assuming the Cnoidal theory assumption ?
********************************************
I have also another question regarding the hydrodynamic loads : I noticed in a lot of documents the following formula (Morison's equation basic case for a lateral equilibrium condition) :
SF *(Fd+Fi) ≤ μ*(Ws - Fl) where SF is a "safety factor" calibrating (Cd and Cm) often equal to 1.1 but sometimes its value changes in other studies.

- Please, could any one tell me how this SF could be evaluated for each case and each depth ? I didn't found any standard which deals with this formula, (the RP-f109 and e-305 use other formulas calibrated with specific Cd,Cm and Cl using the airy wave theory)...

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