Seabed Break-Out and Wave Affected Zone Forces

[marknairn]

I have a couple of questions :-

1/ Does anyone have some rules of thumb for calculating the forces required to break out a piece of equipment from the sea bed when it is being returned to the surface

2/ I'm also looking for information on loadings which will be seen by the same piece of equipment as it passes through the wave affected zone before leaving the water

 

[Ussuri]

1/ None that I am aware of. I expect it would depend on a number of variables, size and geometry of the object, seabed conditions, soil type, embedment into seabed, suction generated. It could be many many times the weight of the object. In which case, you may need to consider mitigation measures, which might include suction dredging to remove excess seabed, some method of breaking any seabed suction maybe HP jetting for instance. You also have all the dynamic forces generated from the snap/snatch effect once the object is freed from the seabed.

2/ You might try DNV Rules for Planning and Execution of Marine Operations. The section on subsea operations gives some guidance on lifting through the water column and effect of the splash zone. Also DNV RP C205 environmental loadings.