Abaqus-tapered pile in sand-half 3d model-question 1

[Lnx3]

Hi
I’m modelling a steel tapered pile embedded in sand (Half-model) using the following steps:
1. Geostatic step for the soil (with the pile de-activetd)
2. Removing the part of the soil representing the pile opening
3. Resetting the displacement to zero (BC). I made this step since very little displacements are left after the geostatic step (in order of 5x10^-4m) so that when I activate the pile in the following step it can fit in
4. Activating the pile
5. Activation of the pile soil interaction properties
Until this point I have no problem, but then when I wanted to remove the soil movement restraint (in step 3) the soil seems to bulge up around the lower area of the pile.
I thought that this could be due to the pile taper where the displacement of the soil created a tiny space from which the soil escaped...I thought of tying the two surfaces using constraints(pile –soil) but I didnt find a way for activating it in a certain step (it has to be activated throughout all the steps)
I also tried not allowing “separation” in the interaction properties however it still didn’t get any better.
I also tried applying a load to the pile so that it slightly moves down and hence closes any opening(in case) but again it didn’t work.
I would really appreciate if you can help me with this. I’m new to Abaqus and I’m really having hard time to run this model

Thanks

 

[AnnaG]

Hi,

Unfortunately, I am new to Abaqus too so I don't know how to fix your problem. The only idea which comes to my mind is to use interaction between soil and pile (tangential behaviour -> rough)
I am struggeling with initial stress for my model (loading test of pile)
Would you be that kind and send me your inp or cae file where you define geostatic conditions?

Thank You in advance
Anna

 

[Lnx3]

Thanks Anna
I never tried the rough surface, I'll try it and let you know ( hope it works,I already tried the no separation option but didnt work..I even tried to the tie option but didnt work cause it has to be activated for all steps so for my case it wasnt working)

for the soil initial stresses, you first define a soil set, then define a "geostatic" step where you apply a load "body force" to the created soil set (enter a value of soil mass density x g in component 3 in the body force window... downward arrows should appear then on the model geometry)
you then go to the keywords file..write before the step line the following :
*Initial conditions, Type=Stress, Geostatic
"the name of the soil set you defined as it appears in eth assembly tree","level1-usually 0", "stress at level 1-0 in case of 0","-anticipated stress at level 2","level 2", "Ko"

hope u find it helpful, let me know if you need any help

Ahmed