No, please do not re-enter the densities for the buried segments.
CAESAR II uses point supports, it does not have a "continuous" support such as a foundation or soil. Point supports will produce deadweight bending unless the supports are very close to one another. Since we assume that the bottom of the trench will carry deadweight, there will be no bending due to deadweight and all those point supports will not be needed. So the soil restraint model focuses on the displacement (thermal)loads. Where there is bearing (e.g. at tees and elbows) we place an appropriate number of closely spaced point restraints (our Zone 1). Where there are no bearing issues, where axial friction controls (our Zone 3), we space our restraints at 100-ODs apart.
Now, if you had some restraints consructed in the buried section of your system, you would have to add them to the buried model - not the original model - as CAESAR II removes all existing restraints in the "to be" buried sections as it "buries" them.
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Dave Diehl