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Effective Stress Tensor

Posted Jun 13, 2018, 4:17 p.m. EDT Geomechanics Version 5.3 4 Replies

Sydney Hi
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Hi; I am trying to simulate stress concentration around the borehole. I have defined the in situ stress tensor by the initial strain and stress subnode, and the pore pressure by the external stress subnode. I want to show the effective stress tensor concentration around the borehole, but I am not able to show the effective stress tensor by exsiting options of stress in plot section. Does someone know how it is possibleto show the effective stress tensor in COMSOL? Thanks;

4 Replies Last Post Jun 22, 2018, 1:44 p.m. EDT
Henrik Sönnerlind COMSOL Employee

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Posted: 6 years ago Jun 15, 2018, 1:40 a.m. EDT

Hi,

If you introduce the pore pressure using the Pore pressure option in External Stress, then it is not part of the the stress computation (it only acts as a volumetric load contribution). That is, the stress you see as for example solid.s is the the stress in the matrix of the porous material, also known as the effective stress tensor.

Regards,
Henrik

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Henrik Sönnerlind
COMSOL
Hi, If you introduce the pore pressure using the *Pore pressure* option in *External Stress*, then it is not part of the the stress computation (it only acts as a volumetric load contribution). That is, the stress you see as for example *solid.s* is the the stress in the matrix of the porous material, also known as the effective stress tensor. Regards, Henrik
Sydney Hi
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Posted: 6 years ago Jun 18, 2018, 11:56 a.m. EDT

Thanks Henrik for replying me back. If I want to see the effect of pore pressure on static stress analysis, should I define pore pressure as a diagonal stress tensor? or I should define my in situ stress tensor as effective stress tensor?

Thanks Henrik for replying me back. If I want to see the effect of pore pressure on static stress analysis, should I define pore pressure as a diagonal stress tensor? or I should define my in situ stress tensor as effective stress tensor?
Henrik Sönnerlind COMSOL Employee

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Posted: 6 years ago Jun 19, 2018, 11:23 a.m. EDT

Hi,

You will see the efffect of pore pressure irrespective of if you add it as 'Pore pressure' or just as a diagonal tensor. The displacements will be the same, but in the first case the stress is 'effective', whereas in the second case it is 'total'.

If, however, you change 'Contribution type' to 'Load contribution only', then you get exacly the same results as with 'Pore pressure', that is an effective stress.

Regards,
Henrik

-------------------
Henrik Sönnerlind
COMSOL
Hi, You will see the efffect of pore pressure irrespective of if you add it as 'Pore pressure' or just as a diagonal tensor. The displacements will be the same, but in the first case the stress is 'effective', whereas in the second case it is 'total'. If, however, you change 'Contribution type' to 'Load contribution only', then you get exacly the same results as with 'Pore pressure', that is an effective stress. Regards, Henrik
Sydney Hi
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Posted: 6 years ago Jun 22, 2018, 1:44 p.m. EDT

I highly appreciate you for giving me such a helpful information.

I highly appreciate you for giving me such a helpful information.

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