Drilling & Existing underground concrete structures

[InDepth]

Does anyone have any thoughts/experience with drilling piles into existing underground concrete structures (reinforced)? The situation is to drill new piles for a secant pile shoring system, but an existing pile is in line with the wall (with no possibility of arching the primary piles).

Can a contractor using CFA drill through a reinforced concrete pile or pile cap? Will he need a high torque rig? Will he have to preinstall a "sacrificial" pile in order to keep the pile aligned when drilling the new piles (equalize friction)?

 

[GeoPaveTraffic]

If the pile and/or cap are reinforced you have big trouble. Typically, you can't drill through reinforced concrete. The steel wraps up on the auger, tears out the teeth, etc.etc.

I suggest removing the pile cap and relocating the wall around any existing piles.

 

[DRC1]

Typically obstructions are drilled with a down the hole hammer. Howver, somethings to consider are, what is the obstructions? If it is a 345 kV duct bank, you may not want to drill through it. If it is benign, What is the effect on the pile system with what may be a large obstruction grouted to the pile?