Battered piles with large lateral deflection

[Kreed14]

Hi all,

I'm designing a retaining wall with battered piles. The piles are fixed in the pile cap, and when I apply the loading in the Ensoft GROUP program, I get an error for excessive deflection. My piles are extending down to a bedrock layer, so ideally, the battered piles would be able to resist this lateral load in axial compression and tension. Is there a reason why my lateral load is being resisted by the soil shear interaction with the pile, instead of going directly into straight bearing?

Any help on this would be much appreciated!

Thanks in advance,
Kreed

 

[1503-44]

Axial loads do not cause lateral deflection, so supposedly the lateral loading of the pile is causing bending resulting in some lateral deflection of the pile. The soil will compress and some bending moment will be relieved from the pile, but it can only be entirely eliminated if, the soil is perfectly rigid and does not compress (full lateral load is taken by the soil), or if the pile has the same angle as the resultant vector of the lateral and axial loads. In that case the high axial stiffness of the pile in relation to soil friction on the pile wall, will cause the pile to take all the load as axial stress alone.


--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."

 

[Kreed14]

Hi 1503-44,

Thanks for you quick response on my question. That makes sense that in order to avoid the pile from going into lateral deflection, the soil would need to be perfectly rigid. It also makes sense that the resultant force would need to be in the angle of my battered pile in order to receive the full loading through axial.

I'm still wondering how my deflections can be so large that it throws an error in the program. It seems that the soil should be able to compress enough to a point where it has enough passive resistance to resist the lateral load. My soil layer is weak sand (low angle of friction). Is the sand layer deflecting too much before it stabilizes you think?

Thanks in advanvce.

 

[HTURKAK]

I am not sure for the axial tension resistance .
If you post a descriptive sketch , you may get better responds.



Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[1503-44]

The apparent soil resistance in the program depends on how it is modeled. Often an upper portion of soil depth is completely ignored to a certain depth. It is often not consolidated. It may also be subject to shrinkage and not in full contact with the pile. Very rigid piles may not deflect enough to activate the soil's active pressure and passive strength may be weak. Ask your geotech what type of model is appropriate for the upper soil layers.

As Hturkak says, a diagram might give us more clues to what we consider is important to capture in the model, omit, or model differently.

--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."