mobilized passive pressure

RE: mobilized passive pressure

Dennis Waterman — Fri, 17 Feb 2023 14:58:39 GMT

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

RE: mobilized passive pressure

Mohamad Raad — Fri, 17 Feb 2023 14:55:06 GMT

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?

RE: mobilized passive pressure

RAMÓN CRONWELL SALAZAR MANRIQUE — Fri, 17 Feb 2023 14:08:55 GMT

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

RE: mobilized passive pressure

pasquale paldino — Tue, 12 Jul 2022 15:48:06 GMT

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

RE: mobilized passive pressure

Dennis Waterman — Tue, 12 Jul 2022 09:43:22 GMT

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

RE: mobilized passive pressure

pasquale paldino — Tue, 12 Jul 2022 07:59:45 GMT

Thanks Dennis for answer. I apologize for not give more information. I have a pile, for each phases in my model i have the normal stress of the interface, how do i determine the maximum passive resistence for each phases (does some correlation exist from tau_max?) ? For each phases i have to do the ratio between the effective pressure and the maximum passive resistence.

RE: mobilized passive pressure

Dennis Waterman — Mon, 11 Jul 2022 15:43:32 GMT

Dear Pasquale,

Unfortunately you didn't give any information on the kind of situation you want to apply this. But generally both active and passive pressure is taken from the normal stress of the interface on active or passive side respectively.

With kind regards,

Dennis Waterman