I have a conundrum. This is my first time running stress on buried pipe. What is the best call in this situation?

A soil report I have gives an Unconfined Compressive Strength (Qu) of 4200 PSF, thus an Undrained Shear Strength (Su) of 2100 PSF (as Su= Qu/2), which would yield a Mu of 3.5 (as Mu=Su/600 PSF).

However, 0.7 is said to be the typical Mu value for clay, and state the obvious, that is a significant difference.

My first inclination would be to use the Soil Report value for my soil model, but now that I think about it, the soil that is used to bury the pipe wouldn't necessarily have the same Undrained Shear Strength, and using Mu=.7 would be far less confining to the pipe.

How should this be handled?

Thanks,
Levi

Before burying the pipe, I suggest seeing what the pipe, nozzles, etc. do with an anchor at the ground/pipe interface. If it passes, great.

Then were you to model it with flexible soil characteristics and it still passes, it's a pretty clear no-harm-no-foul situation.

If, however, you have a design consideration that's highly dependent on soil properties, I would suggest an adjustment to the design so that it's not so dependent.

In any case, I think a Mu of 0.7 and a Mu of 3.5 are going to both result in very stiff ground conditions that yield similar results.