Augered Piles 1

[ctm]

Please advise where can I find information on the characteristics, performance, and design of augered cast-in-place concrete piles for elevating a residence type building

 

[Qshake]

Look up Nicholson (sp?) Construction Co. They've done a lot of auger cast pile and for a wide variety of applications. The engineers at Nicholson have written several papers as well.

 

[KAM_imported]

You should contact the Deep Foundations Institute at 201- 567-4232, or at

http://www.dfi.org.

They have a wealth of information on augercast piles, including specifications, and design aids. The DFI puts on a one day seminar each year dealing solely with augrcast piles. To my knowledge, Nicholson does not install augercast piles. Berkel & Co., LG Barcus & Sons, and Richard Goettle, Inc. are 3 firms that install these piles. The DFI can give you a list of member installers.

 

[dik]

I've used augered cast-in-place piles for clay soils. Ones I'm familiar with are of two types. A short shaft 16"dia and 24" dia. by approximately 15' long. The pile is augered and an attachment called a 'three winged spreader' is attached. This enables a bell to be augered at the end. The maximum diameter of the bell is typically 3x shaft diameter. They are commonly referred to as 'spread bored piles' or 'spread boreds'. The bottom of the bell is designed for end bearing on the soil. Check with local pile installers regarding the shaft and bell size at design time.

The other type of augered pile I'm familiar with are straight shafted piles and they can be 40 or 50 feet long. They can be 12" to 36" diameter and are usually designed for skin friction but sometimes for end bearing if good material and not too deep. Due to differences in soil shear stiffness compared to compression stiffness, shear and compression are not generally used in tandem.

A geotekkie should be able to provide you with bearing values or skin friction values. Skin friction I've encountered has varied from 250psf to 450psf and bearing pressure from about 4000psf to 15,000psf. For end bearing caissons (big belled piles) bearing on glacial till has been as high as 40Ksf (founding surface inspected by geotekkie) and have used 20Ksf on the same soil (non-inspected for smaller shafts)

Larger shafts that are inspected require sleeving with a steel pipe and a minimum sized sleeve (Ministry of Labour Requirement and possibly OSHA or some other authority has a similar requirement) The sleeve is withdrawn as the concrete is placed.

If the soil is competent, it can provide the lateral support. Concrete strength is often 20 MPa and 4" or 5" slump. Some clays have high sulphate and require Type 5 cement. If subject to freeze and thaw, then 5% to 7% air. I've used caisson caps of higher strength air entrained concrete over caissons using a lower strength, non-air entrained concrete.

Reinforcing steel is nominal (I usually use 1/2%) with sufficient ties to keep the bars in place and additional bars at top

Reinforcing steel may not be full length.

I usually vibrate the top 10' to consolidate the concrete against the soil as well as improving bond to reinforcing steel (former is main reason).

 

[emmgjld]

I believe that confusion regarding the name and therefore the installation type and the design criteria has occurred.
KAM is describing an augercast pile, constructed with a medium diameter hollow stem auger. The auger is placed to the required depth and grout is pumped into the hollow annulus, uner pressure, while the aguer is slowly/carefully withdrawn. I have also had experience with the contractors listed. They are very helpful.
dik is describing (and giving good recommendations) for a augered pile (known in some areas as drilled pier, caisson, cast in place pile) which he describes.
The Deep Foundations Institue will also have good information for this type.

 

[dik]

Thanks for the additional info.

I've not encountered this type of pile. Looks like it could be easier to use with granular materials that would otherwise slough into the hole. Any idea of what load capacity or the manner of calculating the load capacity. I'll check with a couple of local foundation contractors to see what info they have.

 

[KAM_imported]

The axial capacity of augercast piles is estimated using procedures similar to those described in the Drilled Shaft Manual by Reese and O'Neill. Again, the DFI has numerous publications that can be purchased off of their website that deal solely with augercast piles. Augercast piles have diameters typically ranging from 12 to 24 inches, but piles up to 36 inches in diameter have been constructed. Allowable compression capacities in Florida range from 50 tons on a 14-inch diameter pile, to 400 tons on a 24 inch diameter pile. Typical installed cost is $1.00 per inch of diameter per foot of length. Piles work well in sands, firm clays, soft rocks. Not good in peats, or soft cohesive soils where shaft may bulge. Piles generate high uplift capacity. Due to cast-in-place nature of pile, these piles must be inspected by a qualified individual in the field. Automated installation monitoring equipment is also available, but not universally used yet due to cost.