[CIG-SHORT] Stress concentration near the fault tip

[Josimar Alves da Silva]

Dear Charles,

Thank you for clarifying the purpose of the fault edge. This was a little
bit unclear. My understanding of the fault edges comes from figure 6.4,
page 86 of the manual, and I try to follow this example on my simulations.

Regarding you other comments, the purpose of the tractions on the left side
is to balance the gravitational forces. Perhaps I should also include
tractions on the lower right side of the domain, where displacements are
also being applied ?

Now, regarding your comment "not applying any normal force to the fault, so
it is not clamped at all", do you mean that I should apply initial normal
stresses to the fault using, for example, the db_initial_stress option ? I
assume that this initial stress would correspond to the overburden stress,
correct ?

I believe that the linear and nonlinear solutions are converging. See
attached log file.

Thank you,
Josimar



On Sun, Nov 6, 2016 at 10:36 PM, Charles Williams <willic3 at gmail.com> wrote:

> Dear Josimar,
>
> The primary purpose of using the fault edge is for faults that terminate
> within the domain.  This allows PyLith to properly form the cohesive
> cells.  Since your fault edge is on an external boundary you don’t need
> this.  It appears that you are not applying any normal force to the fault,
> so it is not clamped at all.  Have you verified that both your linear and
> nonlinear solutions are converging?
>
> Also, what is the purpose of the tractions applied on the left side of the
> model?
>
> Cheers,
> Charles
>
>
> On 7/11/2016, at 1:31 PM, Josimar Alves da Silva <jsilva.mit at gmail.com>
> wrote:
>
> Dear Charles,
>
> Thank you so much for the reply. I am attaching a figure with the correct
> boundary conditions.
>
> My questions is:
>
> 1) What causes the high normal and shear stresses near the fault tip ?
>
> Would it be possible that there is something wrong on the way I am
> parameterizing the fault edge ? I have tried turning on the "edges" command
> on the set up but I still observe the high stresses.
>
> My simulation only runs for 15 years. At the end of the simulation there
> is no fault displacement. However, only the high stress values indicated
> above. I wonder if this behavior is normal because the failure criteria was
> not met ?
>
> Best,
> Josimar
>
>
>
>
>
>
>
> On Sun, Nov 6, 2016 at 1:25 PM, Charles Williams <willic3 at gmail.com>
> wrote:
>
>> Dear Josimar,
>>
>> I am somewhat confused about your boundary conditions.  Are any
>> conditions being placed on the top and bottom boundaries?  Also, it appears
>> that you are applying Neumann BC on the left boundary, rather than the
>> fixed displacement BC shown in your figure.  Is this correct, or is
>> something mislabelled?
>>
>> Cheers,
>> Charles
>>
>>
>> On 5/11/2016, at 11:24 AM, Josimar Alves da Silva <jsilva.mit at gmail.com>
>> wrote:
>>
>> Dear All,
>>
>> I am running PyLith with a 2D fault friction model, including
>> gravitational effects.
>>
>> I am finding stress concentration near the tip of the fault and I would
>> like to understand why this occurs. See attached figure.
>>
>> On the link below Brad seems to address this issue, however it is still
>> not clear to me why this happens.
>>
>> http://lists.geodynamics.org/pipermail/cig-short/2014-Novemb
>> er/001924.html
>>
>> Details about my simulation are attached (log files, boundary
>> conditions...)
>>
>> Thank you in advance for your time.
>> Best,
>> Josimar
>> <pylith_problem.pdf><log.out>_______________________________
>> ________________
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>>
>> Charles A. Williams
>> Scientist
>> GNS Science
>> 1 Fairway Drive, Avalon
>> PO Box 30368
>> Lower Hutt  5040
>> New Zealand
>> ph (office): 0064-4570-4566
>> fax (office): 0064-4570-4600
>> C.Williams at gns.cri.nz
>>
>>
> <boundary_conditions.pdf>_______________________________________________
> CIG-SHORT mailing list
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>
> Charles A. Williams
> Scientist
> GNS Science
> 1 Fairway Drive, Avalon
> PO Box 30368
> Lower Hutt  5040
> New Zealand
> ph (office): 0064-4570-4566
> fax (office): 0064-4570-4600
> C.Williams at gns.cri.nz
>
>
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