Safety factor with Abaqus ? 2

[Hassanalg]

Hi everybody
I am a geotech engineer, I use a program Abaqus, for assessment of slope instability
I want to know this program "Abaqus" give us the Safety factor of this slope ???

Thanks

 

[ntschwanz]

Abaqus can give you the safety factor but since I am not an Abaqus user I don't know whether Abaqus has a built in routine for finding the safety factor. Stress deformation programs do not solve directly for factor of safety, but can be used to find factor of safety through non-convergence of the model. Several programs have built in "c-phi" reduction techniques where simple strength properties (like in a Mohr-Coulomb constitutive model) are continually reduced by some strength reduction factor (SRF). The SRF associated with non-convergence of the model represents the factor of safety.

 

[Hassanalg]

Thanks
for give me this informations
but, i want to know how to extracted the safety factor from abaqus,
thanks

 

[ebenozen]

The short answer to your question is that you are running a finite element model that is not set up to calculate a global factor of safety. You should evaluate stability using this model in terms of convergence and predicted strain which is the purpose of finite element modeling. If you want a factor of safety, do a limiting equilibrium model. This is the best way to compute a factor of safety for a particular slope (Fs=resisting force/driving force).

The method that ntschwanz mentioned (strength reduction method) gets you a factor of safety, but this is not something that you can compare to a factor of safety obtained from a limiting equilibrium analysis. Generally speaking, when discussing factor of safety for a slope it's, by industry standard, determined using a limiting equilibrium model.

 

[Hassanalg]

Thanks
for this informations
yes,i know how to compute a factor of safety for a particular slope with limiting equilibrium model " Geo-slope" and i know how to compute a factor of safety for a slope with strength reduction method "Plaxis".
But keep me know how i extracted a factor of safety with this program "Abaqus" ???

thanks for all this

 

[ntschwanz]

If there is no automated SRF routine in Abaqus you can manually factor Mohr-Coulomb strength values, c and tan phi, by a SRF. When the model no longer converges that SRF is the FS. For models that do not have structural element the SRF approach has agreed well with limit equilibrium results (but you should always do both as a check). Models with structural elements can be more problematic and results may not always agree. When doing the manual SRF approach suggest plotting xdisplacement vs. SRF so you can see when displacements begin increasing with small changes in SRF (remember that displacements are meaningless at the limit state).

 

[Hassanalg]

thanks for all this information

 

[aylee]

Hi Hassanalg, im a beginner and wish to learn slope analysis, don't mind share with me your experience? Thanks lot

 

[Hassanalg]

Hi Aylee, how are you ?
you are welcome