There is a potential ambiguity with 'hydrostatic stress' because the term is also used in a more restricted sense to describe an isotropic stress with a specific value determined by a weight of overlying water. In this sense it is sometimes contrasted with lithostatic stress (due to overlying rock - heavier at any given depth). I think that the use of 'hydrostatic stress' in the restricted sense and also in the general sense sought by Rolf is potentially confusing for students.
The problem with 'pressure' is that the term is also used (particularly by metamorphic petrologists) for the mean stress, even in situations where the stress is anisotropic. Because of this long usage, it's not elegantly possible to use 'pressure' to distinguish between isotropic and anisotropic stress. For example, you can't write that a rock is 'not under pressure' when you mean that the stress is non-hydrostatic, or non-lithostatic, or anisotropic. 'Isotropic' avoids these problems.
John
On 2012-Feb-21, at 2:54 PM, ANTONINO CILONA wrote:
> Dear Rolf,
>
> In my opinion you could keep using the term hydrostatic for a historical point of view. In the literature people refear as hydrostatic to experiments performed without differential stress and pressurized by means of different media (e.g. water, silicon oil, argon).
>
> I think noreferee would correct it...
>
> Cheers
>
> Antonino Cilona
>
>
> Ph.D. Student,
> School of Science and Technology
> Geology Division, University of Camerino.
> Via Gentile III da Varano, 62032 Camerino (MC)
> Off.: (+39) 0737 402619
>
> mob.: (+39) 3470061230
> skype: ninocilona
> www.rechproject.com
>
> -----Original Message-----
>> From: "Rolf Bruijn" <[log in to unmask]>
>> To: [log in to unmask]
>> Date: 21/02/2012 19:08
>> Subject: Isostatic or hydrostatic stress
>>
>> Dear all,
>>
>> In a manuscript I am preparing now, I doubt about the use of the term hydrostatic stress (sigma1 = sigma 2 = sigma 3 = P), because in my case the pressurized confining medium is argon gas and not water as hydro would suggest.
>>
>> So, as replacement for hydrostatic stress I am considering 'isostatic stress'.
>>
>> Could you please provide any thoughts about the validity of the term isostatic stress?
>>
>> Many thanks in advance,
>>
>> Cheers
>> Rolf Bruijn
>
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