60' Composite pile (20 ft PSC with 40 ft HP) driving

[Shakta]

Subsurface encountered a very dense sand layer about 20' below ground level. Instead of predrilling and using PSC section, a composite pile with 20' PSC section and 40' HP section was recommended. Wondering if anyone have this kind of pile driving situation. What kind of challenges may show up during construction/ pile driving. Thanks in advance for your input.

 

[EireChch]

PSC stands for precast square pile for those wondering.

I have never driven a composite pile like that. Can you upload sketch. Id love to see how they are connected.

I imagine it would need some advanced PDA expert to properly model the response to driving, driving stresses etc.

 

[Shakta]

@EireChch, a quick sketch. Thanks!

 

[WinelandV]

Dumb question time: If you're going to have to drive HP section anyway, why not only use the HPs? If it's sand all the way down, the material between the flanges shouldn't (won't likely) plug and there's a fair amount of surface area for skin friction in the HP.

Please note that is a "v" (as in Violin) not a "y".

 

[Shakta]

@winelandv, It will be in water and HP section is not intended to exposed to surface water.

 

[SlideRuleEra]

Shakta - We (bridge contractor) never drove composite piles, except for precast, prestressed concrete with stubby HP points, like this photo from the web:

For composite piles with the dimensions you are considering, the only thing that stands out is that the joint is the weakest place. Any lateral force applied to the pile during driving puts the pile at risk. To compensate for this, make sure that pile alignment (either plumb or specified batter) is maintained during the driving process... no "tugging" on the pile to pull it back into alignment as driving progresses.

Of course driving properties will change when the concrete portions enters the soil, but this should not cause a problem... just something to be noted.