Pile driving at the edge of the world

[amazing azza]

Hi guys, we are continuing our sugar plant build in sunny Indonesia.

We are about to begin work on laying the foundation. Foundation is going to be based on pre-cast, driven, concrete mini-piles. 2 rows of 10x3-pile, and 1 row of 10x2-pile (6m between pile packs lengthwise). Cone penetration testing locates a firm stratum (qc >250 barg) between 2.5 and 6 meters, based on 5 samples (4 corners + center).

1. How to deal with a large variance in depths (compared to overall pile length)? Piles of the size that we're using (250x250mm) come in 3m and 6m lengths, and have steel plates that can be welded together to form a joint.
- Order another round of cone penetration testing and make a detailed map?
- Use all piles at 6m long and just waste the excess?
- Use all piles in 3m long sections and splice as necessary?

2. Installation procedure. The pile cap will sit about 1m below grade, thus excavation will be necessary at some point. Would it be more prudent to:
- Excavate first, then drive?
- Drive first, then dig around the piles? And if so,
- Drive to below ground using an attachment?
- Drive above ground and cut to length once excavated for pile cap?

3. Should I validate the driving equipment before starting, ie. check the theoretical hard stratum depth vs actual driven depth? The contractor is planning on using a drop hammer driven by an electrical winch/roll with an operator that keeps pulling/letting go of a lever. It is quite rinky-dink compared to the kind of equipment you are probably used to. Nevertheless, that is "the standard" around here and it even seems to work...

 

[1503-44]

That's going to be driven by cost of cutoff vs cost of field labour for welding extensions and the confidence you're willing to invest in your field work.

I'd excavate first. Far better than trying to drive heavies around and between piles.

If you're going to validate, do that before ordering piles.

 

[HTURKAK]

Q=1. How to deal with a large variance in depths (compared to overall pile length)? Piles of the size that we're using (250x250mm) come in 3m and 6m lengths, and have steel plates that can be welded together to form a joint.
- Order another round of cone penetration testing and make a detailed map?
- Use all piles at 6m long and just waste the excess?

A= If firm stratum at max. 6m . below, better to use 5 m long piles or if you have two options, ( 3 m and 6 m) , i would suggest you ; prefer 6 m.

Q= 2. Installation procedure. The pile cap will sit about 1m below grade, thus excavation will be necessary at some point. Would it be more prudent to:
- Excavate first, then drive?
- Drive first, then dig around the piles? And if so,
- Drive to below ground using an attachment?
- Drive above ground and cut to length once excavated for pile cap?

A= prefer Excavate first, then drive if the excavation area is large enough for piling rig operations. Or, you may prefer driving with attachement ( Jocker pile , steel pile with 3.0 m length ..)


Q= 3. Should I validate the driving equipment before starting, ie. check the theoretical hard stratum depth vs actual driven depth? The contractor is planning on using a drop hammer driven by an electrical winch/roll with an operator that keeps pulling/letting go of a lever. It is quite rinky-dink compared to the kind of equipment you are probably used to. Nevertheless, that is "the standard" around here and it even seems to work...

A=The contractor should convince that the proposed driving eq. is suitable ..may be with tech. data of the eq., past projects ..

 

[SlideRuleEra]

1. Use all piles at 6m long and just waste the excess. (Excess is not "wasted". It avoids actual wasting of time, labor, equipment and material needed to extend the pile, needlessly creating a future corrosion problem with the buried welded joint... and the extension may have to be cut to elevation anyway.)

2. Excavate first, then drive. (Rule of Thumb: Perform any underground work as quickly as practical - there are too many "bad things", like flooding rain, that can go wrong. Keep it simple; excavate, drive/cut off the 6m piles, backfill and get out.)

3. Validate the driving equipment before starting. (Otherwise called "index piling". Drive at several site locations. You want to have the pile driver/ operator prepared for this project and "ready to go", see #2 above.)

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