Hi Navid,

the first question is "why Flac shoud calculate the horizontal stress for you?"

Geotechnical engineering is more complicated than elastic materal theory, and one the first step is the judgment of the engineer in the definition of

- how he wants to simulate a given condition

- and the state of initial stress.

Then we can start:

- in your problem the gravity is negligible ? (shallow : NO, and then you need gradient, deep: YES).

- and in deep condition, remember that results are different if you apply stress and roller boundary than apply directly the stress at boundary.

- are you in soils or rock ? In soil you can apply SXX=SYY=(1-senf)*OCR^a

in rock you must do assumptions on the tectonic history. I've read several articles on the in situ stress on the sidney area.

The think NOT to do is apply gravity and boundary fixities and let flac calculate the horizontal stress. In the lucky case you have sxx=syy=v/(1-v) , in the worst case complete plasticity and not relaible results.

The v6 gives to you a wonderful command for initialize tension with defined ko

e.g.

model gravity 0 0 -10

zone initialize-stresses ratio 0.5

and if you are in deep condition:

;top of the model pressure

zone face apply stress-normal -27982500 range position-z 64.9 65.1

;init tension

zone initialize-stresses ratio 0.75 overburden -27982500

hello

How to calculate initial stresses for different layers with different density for slope?