Max. depth of 14" auger cast pile

[JAE]

The IBC states that the maximum length of an auger cast pile is 30 x diameter. For a 14" diameter pile, that is 35 feet. (see section 1810.3.2 of the 2006 IBC)

There is an exception to that where the IBC says that if a design professional with knowledge in the field of soil mechanics and pile foundation directly supervises the pile installation and certifies that they were constructed per the plans/documents, then it is OK to extend past the 30d limit.

Is this just a cautionary limit or are there major pitfalls with exceeding the 30d?

 

[dik]

16" dia by 50' are common in these environs...

Dik

 

[molerat2210]

That is a cautionary limit. 60d or more seems routine in my part of the world.

 

[aeoliantexan]

We used some ACIP piles 120 feet long to support a linear accelerator addition to a hospital, They were either 16 or 18 inches in diameter. They went through about 90 feet of loess and into glacial till - pretty ideal conditions. We had to break augers each time to get that depth.

We also used 18-inch ACIP piles 80 feet long in floodplain alluvium - 20 feet of silt and clay underlain by sand. The water table was above 10 feet.

In both cases, the reinforcing was a small cage about 15 feet long, as was common practice at that time and place. No full-length center bar was used, and I doubt if one could have been because the grout tends lose a little water into those formations and get harsh.

 

[Ron]

JAE...for consistent strata, there's not an issue with running a 14" dia. ACP to 50 feet or so. I would only be concerned if you had a thick, very soft stratum over a hard bearing layer.

 

[jgailla]

I've designed (geotech, not structural) ACP piles 16" piles 80 feet long.
I've also observed the installation of piles of the same depth in coastal Georgia.
The biggest problem was getting the 25 foot long cage into the top of the pile after the auger withdrew.

 

[dik]

For the reasonably competent soil that we have, my rebar cage consists of 4-25M by approx 10' long held together by a cage of 10M bars. The length was chosen as a multiple of bars coming from a 12m or 18m length...

Dik