Hi all,

I am doing stress analysis on a system that contains a significant portion of buried piping. It has lead me to some questions that I cannot find answers for in previous forum posts.

1. If I have a circumferential protrusion on buried pipe (lets say a flange), what is the best way to model this protrusion to capture the drag effect in the soil. I'm thinking of testing the below options:
a. Add pipe branches to the header which protrude from the header with an equal cross sectional area to the circumferential protrusion, and classify these as Zone 1 in buried model.
b. Add a pair of reducers on the header that increases the OD of the pipe to the same OD as the thickness of the flange/protrusion.
c. Add insulation locally in place of the flange/protrusion and set to Zone 1 in buried model, and classify them as Zone 1 in buried model.
I am running tests at the moment but the queries below leave me to doubt my results.

2. Is the insulation thickness used to increase the effective OD of the buried pipe and hence impact the lateral push on pipe (zone 1) or the axial friction (zone 3)?

3. If I have run the 'Underground pipe modeler', and then want to make a change to the buried piping (e.g. increase insulation thickness or add a buried reducer), can I just rerun the B file in the 'Underground pipe modeler' again, or do I need to make the changes in the 'pre-underground modeler' stress model, then put through the 'Underground pipe modeler' again?

4. Is there a way to clear all the soil restraints quickly?

5. If the restraints are removed automatically by the 'Underground modeler', why does it not remove all the soil restraints when I run the B file again with no buried elements selected?

6. Is the Zone 1 (lateral push zone) only important for non-circumferential geometry (e.g. tees, bends) or does it also need to be applied to circumferential geometry (e.g. flanges), reducers.

7. If I am to set a Zone 1 region, do I need to calculate the 'lateral bearing length' myself using Lb = 0.75(π) [4EI/Ktr] 0.25, and then add nodes at these positions in the model, or does the 'Underground Pipe Modeler' do this?

8. In the training notes it suggests to use WNC instead of W+P1 as the baseline for the stress range loadcase. Why is this? Is it something to do with the underground modeler removing pipe and fluid density? I have read that the WW overrides the zero fluid density.

9. If I add Zone 1 myself, does the 'underground modeler' automatically calculate the Zone 2 lengths.