The main difference is that in an auger cast pile, the grout is pumped in through a hollow stem auger, filling the hole as the auger is withdrawn, whereas in a drilled shaft/drilled pier the auger is removed leaving an open hole that is then grouted afterwards.
Augercasts are typically used in non self supporting soils. I've seen them used in the peat soils up in Seattle. Geologists call them "Peaty soils", a great word.
Caltrans goes the whole show one further with "Cast in Drilled Hole" (CIDH) piers.
You might also review the IBC code (if you are in an area that uses it) as it makes a distinction between "pile" and "pier" based on length vs. diameter.
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Auger-cast has long, continuous flights and, as Hot Rod said, the pier is grouted as the flights are removed.
Drilled piers tend to be more like a 720 degree flight at the end of a long shaft where a little soil at a time is drilled, pulled up to the surface, and spun off the flights. The assembly is re-inserted and this is repeated until you reach your depth.
Drilled shafts tend to be larger in diameter (almost no upper limit) where auger cast is limited to ~ 36".
The bottom of a drilled shaft can be inspected before the concrete is placed whereas auger cast cannot. This is why test "piles" for auger-cast are often required.
It is a bit of a prejudice, but in my mind, a pier is something more scientifically and theoretically conceived, designed, calculated, installed, advanced, and all those other thoughtful, deliberate words.
Piles and pile drivers on the other hand are a horsepower and testosterone affair with lots of gitter done attitude and **** waving about size and length. Those guys don't stop hammering til they get refusal of earth or equipment or the end of the pile bursts up out of the ground somewhere.
And that is not to say one is better than the other. Somehow there is a certain beauty to the tested capacity of a driven pile over the calculated capacity of a pier.
Can you interchange the equipment's auger attachment to change from auger cast piles to drilled piles, vice versa? I want to know more about the equipment used for drilling auger cast and drilled piles specially the size and head clearance required. For example, I have same 2ft diameter and 15' length. Which would be preferred to use?
You can use the same crane but not the equipment. Auguer cast piling use a flight auger system - typically a long vertical box truss with a long continuous flight auger within.
Drilled piers use a much shorter (but usually wider/larger) bit to drill the holes with a long "Kelly" bar - a square tube.
Auger Cast setup:
Drilled Pier setup:
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"I didn't understand when you said same crane can be used."
More common for both is a trackhoe-mounted rig, although suspending the rig from a crane can also be used (typically for sites not accessible to a trackhoe or truck-mounted rig). As you can see from the picture of the auger-cast setup, it is mounted to the boom of a trackhoe. Larger drilled shaft auger rigs are often mounted in similar fashion.
