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mobilized passive pressure

pasquale paldino
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hy,

I need to determine the ratio between effective pressure (sigma_N to interface) and passive pressure (maximum resistence). For passive pressure i do not know how to calculate with plaxis (take sigma_v and calculate to hand maybe?) . Did someone ever resolve this situation?

Thanks a lot.

PP

  • Offline in reply to Mohamad Raad

    Dear Mohamad,

    For a cross section the stresses are determined by interpolation of the stresses in the soil elements where the cross section passes through. For the interfaces we actually directly calculate the stresses, hence interface stresses are more accurate than cross section stresses.

    Best regards,

    Dennis Waterman

  • Offline in reply to Dennis Waterman

    Dear Dennis, a following question came up to my mind. What's the difference between taking the normal stress from the Interface and taking it from a very close cross-section (cross-section total normal stress)? Do you recommend each method for a specific case or goal?

  • Offline in reply to Dennis Waterman

    Hi Dennis and Pasquale

    I have a similar situation with a COMB-WALL (pile kings and sheet steel piles) for a quay wall, We need to calculate the SF of passive earth resistance. Buy I have some issues for modeling the pile load test (PLT):

    1. I have the COMB-WALL modelling with Plain Strain. How should I model the pile load test? PS or Axisymmetric?

    2. I am thinking of modelling the PLT in the final condition of the COMB-WALL, it means after the dredging is done. Is that correct? What loads do I have to use to simulate the PLT?

    3. Modelling pile as volume element with interface

    I would really aprecciate some of your advices for these issues.

    Ramón Salazar

  • Offline in reply to Dennis Waterman

    thanks a lot Dennis for the answer. I appreciated it.

  • Offline in reply to pasquale paldino

    Dear Pasquale,

    The simplified theoretical maximum passive resistance can be calculated as Kp*gamma*h where the coefficient Kp is can be calculated using for instance Rankine or Bell. But that value doesn't change per phase ...
    In reality, compated to theoretical solutions, the maximum passive resistance depends on a lot of factors like the cross section shape of the pile (circular, square) and whether the soil is cohesive or not. Taking all that into account is not possible in an anaylitical solution - then the only way is to just simulate a pile load test (in PLAXIS) to determine the maximum passive resistance and then per phase compare it with the actual effective stresses to get the ratio.

    With kind regards,

    Dennis Waterman 

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