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Subsea Pipeline & Seabed Lateral & Axial Resistance

atedionyahoo (Mechanical) (OP)
24 Feb 10 1:20
In general, how the lateral & axial friction between subsea pipeline and seabed is extracted based on geotechnical survey data, i mean break out (static) and residual (dynsmic) resistance. NB, I have noted to SAFEBUCK JIP report 2005 (lateral buckling), but it is for specific condition of clay and sand.

The other question, ref to DNV-RP-F109 (oct 2007, sec 3.4.6), regarding passive resistance, it is unclear how the break out and residual resistance is calculated?, the provided calculation for passive resistance is unclear that it is relevant to either break out OR residual resistance?
 
BigInch (Petroleum)
24 Feb 10 5:15
You'll have to ask your geotech consultant specifically to do the tests necessary to provide that data.  For that you'll have to obtain drop core samples at regular and specific points along the route.

I'm not up on the specifics of the DNV 109 code, but I think you are referring to active and passive pressures of the soil.  Passive resistance is the pressure exerted by the soil on a pipeline or structure when it is at rest and there is no movement of the structure into the soil, basically just the equivalent pressure directional components from the dead weight of the soil.  Active pressure is the resistance applied by the soil to a structure that is moving into and usually applying some uplift to the soil typically from moving in a lateral, or lateral and slightly upward direction into the soil.  Any basic geotechnical text discusses the methods of determining those pressures from the soil properties.  The only tricks involved can be getting good soil samples extracted from deep water.  A hollow point dart device is usually employed and dropped from the survey boat during the route survey.  The dart is hauled up and samples removed, wrapped and stored for later labratory analysis.  Bring spare darts if you think there's some rock down there.

**********************
"The problem isn't working out the equation,
its finding the answer to the real question." BigInch
http://virtualpipeline.spaces.live.com/

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