How Adonis calculate horizontal stresses in the initial stress state?
I suppose using earth pressure coefficient at rest k0 but i didn't find it anywhere.
Do Adonis automatically calculate it or can i change it?

Enzo

ADONIS does not use K0 value. it's user's responsibility to apply the vertical and horizontal insitu stresses accordingly (K0=sxx/syy). you can use GUI for applying the initial stress or you can write a simple script to read the vertical stress from each element and apply the horizontal stress based on given K0 (sxx = K0*syy). second method can be used if different K0 value needs to be used for different regions.

Ok!
So with command "setgravity" I apply vertical stresses, then I have to apply manually horizontal stress according to k0 procedure. If I stop to setgravity without applying horizontal stresses I will expect to have sigmaxx=0 but when I solve the model I have values different from 0. Why?

how do you get stress in your model at first place if gravity is turned off? are you using any other external loads in the model?

in case you apply any kind of external loads in your model horizontal stress will be generated regardless. you need to read some FEM of material mechanics books if you want some more detail on this topic.

No, I don't have any external loads.
Maybe I have not been clear with my problem.
This is my script: as you can see, I applied gravity force and no external loads.
Thank you for your helpfulness.

I just commented out the gravity (see attached file) in your script and re-ran it. all the stresses in the model are zero as expected. please note that in the contour plot range of number will be reported in the legend for sack of presentation but the actual value in the model is zero. if you look closely to the color and also to make sure you can export the text file from the contour pot dialog and check the values. they should be zero.