Hello everyone,

I am trying to design a buried pipe with the ALA parameters and currently I have no idea what values to use when CAESAR asks for the yield displacement factors (dT, dP, dQu, dQd). I understand that they are either a multiple of H or D based the deflection that induces maximum allowable force, but how are these deflections found in the first place? Please help explain what I need to put into these fields. Thank you very much for your help.

Get a copy of the ALA document that developed the values used in CAESAR II. Check out Appendix B. It's available (pdf) on line. Google "ALA buried pipe"; that phrase brought the document to the top of the list on my PC.
The CAESAR II Help for the items show the ALA's recommended values. For a first pass on your system, these ballpark values will get you started. I would hope you have some civil engineers backing you up on these and other soil terms.

Thank you very much for your quick reply Dave,

We did see the suggested values from ALA and CAESAR. However, we are dealing with a muskeg area with pure peat at the level of our buried pipe. That is why our civil engineer believes that the suggested values are not suitable.

If these values defines how stiff the soil spring is, would all the yield displacement factors be higher than normal for loose and soft soil like peat?

This yield displacement term sets the distance the pipe can move before the ultimate load-carrying limit of the soil is reached.

I don't know much about peat (except in my Laphroaig) but if it is spongy I might go to the high side of those numbers. If it crushes quickly, then a small number.

A simple approach would be to run a few sets of numbers to see how much these terms affect your model.