https://communities.bentley.com/products/geotech-analysis/f/forum/235005/effect-of-overburden-and-confining-stress-on-hss-model-parametersFor the hardening soil and hardening soil with small strain models, PLAXIS material models manual states that the Pref = 100 kPa in PLAXIS (and it is better to leave it at that) and also Pref = confining stress in a drained triaxial test. I am conductingen-USTelligent Community 12https://communities.bentley.com/thread/731332?ContentTypeID=1Mon, 12 Sep 2022 18:08:01 GMT6dad98f5-dbc9-4c4d-a9ba-e9da8dc6aa8e:115b8407-c212-48d5-ac6a-a41347375e4aFaseel Khan<p>PLAXIS uses pref = 100 kPa by default which is 1 Bar (atmospheric pressure). And this pressure has been typically used in the literature as 100 kPa. In the triaxial test pref = Sigma&prime;3 . The actual stiffness depends on the minor principal stress Sigma&prime;3 which is the confining stress. At this reference stress of 100 kPa, for oedometer conditions of stress and strain it can be assumed that Eoed-ref = E50-ref.</p> <p>pref the reference stress used to scale stiffness moduli Eoed-ref, Eur-ref, E50-ref to current values with respect to a current minor principal stress Sigma&prime;3 . The reference pressure of 100 kPa is the same for all the three stiffness moduli. In some cases it may be necessary to change the reference pressure for example in deep excavation situations where higher horizontal effective pressures are reached at deeper depths and it may be suitable to use a smaller value for reference pressure.</p><div style="clear:both;"></div>