Criteria for Dynamic Slope Failure

Question

Hi, 
 I am using PLAXIS 2D to perform earthquake time-history analysis for a slope using different accelerograms. As a result of this analysis, I will need to estimate the potential volume of soil that may fail and mobilize as a result of the earthquake event. Could you please help me on what criteria to use to identify to potential soil failure surface? I was thinking of using a horizontal displacement criteria but I am not sure what displacement to use to identify fail/unfail situation. I can also look at the cartesian strains but I am not sure about what limiting value to use. 
 Could you please provide some guidance or may be direct me to some references which dealt with the same type of problem?

Sean Johnson · Answer

Hi Mustafa, 
 
 As the time-history is applied, a variable acceleration input imparts stresses in time domain. Normally, when we investigate a failure envelope, we inspect the incremental shear strain output. The output gives and an indication of the proximity to failure. The reasons you can see regions as the time history gets applied may or may not mobilize plasticity. When failure occurs you will see a large shear strain increment for a given calculation increment. Those areas (and the model in general) needs to be more inspected. 
 It is also very important to have the &lsquo;saved steps&rsquo; field set as large as possible in the calculation control parameters to track the development of the failure envelope as the time-history gets applied to the model.

Criteria for Dynamic Slope Failure

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