why I am getting higher FOS instead of getting lower value?

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LaboniGupta
LaboniGupta Posts: 1
in GeoStudio

I am doing a slope stability analysis. I am trying to compare the factor of safety including seepage and without seepage. First, I calculated FOS using slope-W and I got 1.290 but when I used the seep-w results to do another slope w analysis and I am getting 1.445 when I am including seepage effect. Why am I getting higher FOS instead of getting lower value?

Geostudio.docx

. I am adding the screenshots of my analysis.

Best Answer

  • TrevorKent
    TrevorKent Posts: 30 Diamond Rank Badge
    Answer ✓

    Hi @LaboniGupta, I apologize for the delay. One of the reasons you're seeing the factor of safety increase is because the piezometric surface is lower in the SEEP/W model than the piezometric surface model. If you change the SEEP/W model so that the piezometric surface follows the ground surface, the factor of safety decreases.

    However, the SEEP/W model FOS is still higher than the piezometric surface model FOS. This is because when there is a downward flow regime, SLOPE/W calculates higher pore water pressures from piezometric surfaces than SEEP/W calculates. You can read more about this in the PDF I've attached. Please let me know if you have any other questions.

    Pore-Water Pressures Defined using a Finite Element Analysis.pdf

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