We have encountered a slope failure in the dam after its operation for 10 years (after rapid drawdown) .The failure might have occurred due to cyclic movement of water for long time followed by Rapid Drawdown ; Strength of the soil is assumed to be near the residual state.
I would like to model this case in Finite Element program and would like to request for best Numerical Model that can be used.
I suggest to use the coupled analysis with sigma/w and slope/w in Geostudio. You can model both the cyclic movement and the rapid draw down as the boundary conditions. Plz test & update the result.
hello Kobid Panthi, which type of material shows 'strain softening' behavior? clay-core or rockfill?
In the first case you can use modified cam clay constitutive model, (Flac and Plaxis and sure other can implement it), for compacted cohesionless material of rockfill you should use constitutive model with dilatancy.
I encountred some difficulties to implement clay-core in models becouse clay-core is compacted at w-optimum and is subjected to viscous behavior during constructing and during life.
In both cases, models implementing softening, and coupling with transient water flows, model could result much "unstable".
I suggest to start with simple mohr-coulomb and couple it with water flow. Then lower manually peak to residual parameters and tep-by-step implement more suggestive constitutive models.
hope this helps.
Using Modified Cam Clay in Plaxis and Sigma/W in Geostudio. Because dam core is clay which is suitable for 2 models was suggested.
Good luck sir
You have to check the manuals of the calculation programs if the model you need is available. Many software mentioned in the answers above include the "cam-clay" (0). Is that what you need? Do you have the data necessary for the implementation? Or do you want to apply a 'mohr-coulomb' with resistance/stiffness degradation? and in this case, the reduction must be immediate (1) or with progressive reduction as a function of shear deformation (2), or (being next to the residual parameters) is sufficient the degradability of the deformability module (G / Go) (3)?
In my experience (I dont' use geostudio), the answers are:
(0) almost of all sw
(1) flac, Phase2/RS2
(2) flac,
(3) flac, Plaxis, RS2
Take a look on constitutive models available:
https://www.rocscience.com/help/rs2/#t=getting_started%2FMaterial_Models.htm
http://downloads.geo-slope.com/geostudioresources/books/10/0/SIGMA%20Modeling.pdf
https://www.itascacg.com/sites/itascacg.com/files/ICG16-BRO-FLAC-800-Web-02.pdf
https://www.plaxis.com/?plaxis_download=2D-3-Material-Models.pdf
Look first what you have in the university (maybe in the university you have Abaqus and someone who can give you assistance in using it), and then choose.
Filippo Forlani Thank you for your suggestion. I used MCC model and was able to determine the phenomenon of strain accumulation at the slope where it had failed at the site. And interesting thing was that, the strain accumulation was not seen in the zone where it did not fail. But in my case the shear strength of the failed zone ha undergone some reduction in strength but has not reached the residual state . Since MCC model assumes cohesion value as zero, it it the best model to incorporate the condition of Strain Softening?
dear Kobid Panthi MCC soil if preconsolidated shows something like a cohesive behaviour, with peak (and maximum of dilatancy) and residual.
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