If your material is clay then I'd say it is sensible to go for undrained conditions for short term analysis, but then if I'm not mistaken the cohesion the software expects in this case is actually the undrained shear strength, not the cohesion intercept on the failure envelop plot in term of effective stress parameters.

Hi

Yes, that's right

Hi Bruna,

Thank you for response. Based on your explanation, I take it that its more appropriate to select the Mohr-Coulomb model rather than the phi=0 case i have indicated.

Dear Jessie,

I would like to add one point to the discussion that if design requirement is to verify the slope stability for short term performance then undrained condition alright. But, if you want to verify the stability of slope for long term then in this case you prefer to analyse the slope in drained condition rather than in undrained condition. ok all the best in your research..

The strength parameters c and phi can be total strength parameters or effective strength parameters. SLOPE/W makes no distinction between these two sets of parameters.

From a slope stability analysis point of view, effective strength parameters give the most realistic solution, particularly with respect to the position of the critical slip surface. The predicted critical slip surface position is the most realistic when you use effective strength parameters. When you use only undrained strengths in a slope stability analysis, the position of the slip surface with the lowest factor of safety is not necessarily close to the position of the actual slip surface if the slope should fail.

When you are doing a “Staged Rapid Drawdown” analysis, you must use the Mohr-Coulomb strength model in SLOPE/W. In this case, c and phi are the effective strength parameters, and you must enter the Total c and Total phi to represent the undrained strength of the soil. Using a zero Total c and Total phi signifies that the soil is a “free drained” material in a “Staged Rapid Drawdown” analysis.

Most failures in rocks are due to shear failure, both in static and dynamic stess.

Hi All, I have learned and gained useful insights from your comments. thank you so much for your help and support.