Drilling Through Raft Slab Rebar - Repair Methods

[skeletron]

In a current project I'm dealing with an existing 18" raft slab r/w 20M @ 10" top, 25M @ 16" bot. As part of the new (replacement) machinery, there is a call to anchor these little motors to the slab. The issue that is coming up is that the Client is stating that the motors position needs to be fixed and, because of that, they need +/- 6" holes cored to allow for the tolerance of the position. They want to core through slab and top slab steel at (4) locations.

I'm opposed to drilling through the rebar, but I'm also preparing myself to search out for a repair solution. My current thoughts:
1. Drill in rebar and epoxy new rebar to "lap" next to the cut bar (probably not enough length to get anything meaningful)
2. Rebar couplers (never used these, and not sure you can bridge the 6" gap)
3. Grout the hole with some sort of fiber-mix (not sure I can quantify this other than it feels better than regular concrete)
4. Don't worry about it because it's max 4 cut bars over a much larger area

Anyone see a way to make this work with a legit mechanism?

 

[Klitor]

They should come up with a better solution for Anchorage.
I would understand leaving the 6" pockets on top of raft if it was a new build...but for this...there IS a better way

 

[Tomfh]

4 unless you genuinely need those bars.

Do you have specific concerns about the slab’s strength and stiffness?

Alternatively can you use wider plates for anchoring to dodge the bars?

 

[SlideRuleEra]

4. Don't worry about it because it's max 4 cut bars over a much larger area.

A mat foundation is the ultimate in redundancy for small "damaged" (in this case, drilled) areas. There are plenty of load paths (semi-infinite) to redistribute load that was carried by the cut bars around the hole. I would not be concerned, just properly grout the holes.

 

[WesternJeb]

See snip below for a project I did successfully last year without much complaint. This used couplers on an elevated slab, so a little different though. We determined a 4'-0" square removal was needed for adequate installation, for lap lengths, etc. to help us sleep well at night.

This probably shoots down your option 1 and 2. I'd go with option 4.