# Initialize stress condition between soil layers having different constitutive model

**URL:** <https://forum.itascainternational.com/t/initialize-stress-condition-between-soil-layers-having-different-constitutive-model/1541>\
**Category:** Uncategorized\
**Created:** [June 20, 2024, 2:51am UTC](https://forum.itascainternational.com/t/initialize-stress-condition-between-soil-layers-having-different-constitutive-model/1541 "2024-06-20T02:51:01Z")\
**Posts on this page:** 2\
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**Author:** ![Newuser](https://avatars.discourse-cdn.com/v4/letter/n/3e96dc/32.png) [@Newuser](https://forum.itascainternational.com/u/Newuser)\
**Post date:** [June 20, 2024, 2:51am UTC](https://forum.itascainternational.com/t/initialize-stress-condition-between-soil-layers-having-different-constitutive-model/1541/1 "2024-06-20T02:51:01Z")

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[@itascan](https://forum.itascainternational.com/groups/itascan)  
If I have several layers of soft soil with two constitutive models mohr-coulomb and modified cam clay, arranged in an irregular pattern (cam clay between mohr coulombs and vice versa), is it okay to initialize initial stress by simple zone initialize stress command and assigning gravity for any layers irrespective of their positions? I have seen examples where the pressure-effective for cam clay is calculated separately, so how to initialize stress in soil layers arranged in irregular pattern of constitutive model?

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**Author:** ![jwang](https://avatars.discourse-cdn.com/v4/letter/j/b782af/32.png) [@jwang](https://forum.itascainternational.com/u/jwang)\
**Post date:** [June 21, 2024, 8:04pm UTC](https://forum.itascainternational.com/t/initialize-stress-condition-between-soil-layers-having-different-constitutive-model/1541/2 "2024-06-21T20:04:17Z")

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You can use zone initialize stress command to initialize stress, however, for the modified cam clay model, the mean effective pressure must be initialized before stepping, this can be done via a fish function:

fish define camclay\_ini\_p  
loop foreach local p\_z zone.list  
local mean\_p = -(zone.stress.xx(p\_z) + zone.stress.yy(p\_z) …  
+ zone.stress.zz(p\_z))/3.0 - z.pp(p\_z)  
zone.prop(p\_z,‘pressure-effective’) = mean\_p  
endloop  
end