EXCAVATIONS AGAINST PREVIOUSLY CAST AUGERED PRESSURE GROUTED PILING 1

[dylansdad]

Foundation contractor has previously cast what is known as augered pressure grouted (APG)piles.
Construction activities for the erection of precast items require that a sloping excavation occur in the vicinity of and exposing the upper 4'of a row of piles. Being the GC, we are concerned that the integrity of the piles might be compromised. FWIW the piles are 16" diameter, 35' in length and at a 6' spacing perpendicular to the attached sketch. I would appreciate any thoughts on our concerns.

 

[JAE]

dylansdad:
A few thoughts:

1. Auger cast piling is typically not supplied with circular ties or spiral reinforcement. They are not designed as "columns" per the codes but assume that the earth provides a level of confinement around the pile. If the pile is under load, and you exposed an upper length of pile, you run the risk of a pile failure.

2. Piling like this also are often designed with their capacity based on skin friction along the pile length. If you remove some of the soil at the top, the skin friction capacity may be reduced. The upper lengths of piling are sometimes neglected due to uncertain soil conditions, wetness, frost, or soil disturbance. You would have to check with the engineer who designed them to know what was counted on in design.

3. By removing soil to one side, there is the possibility that you would create some level of lateral soil pressure on the pile (from the remaining soil on the far side) which could rotate or damage the pile. The amount of removal you show isn't all that much but again - I'd check with the engineer-of-record.

4. By excavating near the piling, you run the risk of moving earth around the pile - again possibly reducing skin friction capacity or simply cracking the pile.

 

[dylansdad]

JAE,
Thanks for your comments.
A Dallas Cowboy for you.

Dd

 

[JAE]

Appreciate it! ...but a Viking horn would be better don't ya know.