Hi all,
Anyone can tell how to make the soil heave due to unloading in the soil (because I need to see the soil heaving due to pile driving in soft clay layers)? how to use plaxis to make the soil heave after the removal of high pressure from the soil?
Load applied
but after load was removed I couldn't get a considerable amount of heave.
Thanks.
Dear Nitharshan,
The heave is not caused by unloading, but because in the reality the pile doesn't replace the soil, but pushes the soil aside and that soil has to go somewhere. For the upper soil the soil will mostly go upwards which is the heave observed.In PLAXIS if a pile is modelled by replacing the soil (change material set from soil to the pile material) there is no side pushing of the soil, hence no heave. To get heave for instance a volume strain should be introduced to model the additional volume (of the pile) that is introduced by driving the pile.
With kind regards,
Dennis Waterman
Dear Mr. Dennis,
Thanks for the reply, can you please explain how to calculate the volume strain if we do pile jacking of pile with D=500mm and per meter length as shown below?
Noted, thanks
Dear Mr. Dennis Dennis Waterman
Please check the below method (prescribed displacement => alternation for the volumetric strain method) and let me know whether this approach is okay or not.
Why would you fix the horizontal displacement along the pile? There is an undisturbed soil mass in which a pile is inserted. What would happen with the soil? Your model says that all soil is being pushed downwards... if that would be the case, how would you then get heave?
I fixed the horizontal displacement of the pile element to represent the pile is the rigid element because when we jack the pile, it won't strain in the horizontal direction as well as vertical direction with a considerable amount. With that, I need to see the effect of the soil push due to vertical jacking force only.
As indicated in the screenshot attached in my previous reply, the soil moves along the shear surface and comes above (heave).
I think you should consider how the soil behaves in reality, and how a continuum behaves in Finite Elements. On the other hand, you calculate a heave - how does this heave relate to what you measure in the field? If they match that is great, but then you have to ask yourself the question whether they match because your model is correct or whether they match out of coincidence.