Underpinning contractor did not leave room for drypack 3

[Ben29]

The underpinning contractor installed 14 pits so far. The inspector just now told me that the contractor is not leaving room for drypack. The contractor is trying to do avoid this step. Should I make him sawcut the top 2 inches of the underpinned pier in order to drypack it?

 

[phamENG]

Do you have good, consistent bearing between the pier and the structure above?

 

[Ben29]

no - we cannot tell.

 

[PEinc]

The inspector waited way too long to report non-conforming work.
You could drill a couple of long, horizontal, small diameter holes right at the bottom of the existing footing to see if there is underpinning concrete against the bottom of the footing. If not, use the drill holes to grout the gap.

http://www.PeirceEngineering.com

 

[Ben29]

PEinc: so 1" diameter holes at 6"o/c?

 

[dik]

Can you use flowable pressure grout?

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[PEinc]

Ben29, I would use a smaller drill hole, maybe 3/4" diameter max with two drill holes per each underpinning pier. If a void is found, pump stiff grout into one hole until it comes out the other hole.

http://www.PeirceEngineering.com

 

[Tomfh]

Can’t you squirt something else in there?

 

[JoshPlumSE]

Can’t you squirt something else in there?

That's an interesting idea... Like the type of thing used for repairing structural cracks? That might be a good idea. I'm not sure of costs. It might not be cheap compared to other options. But, it would definitely save some time. Right?

 

[GeorgeTheCivilEngineer]

Non-shrink grout and inform them that the drypack is an important part of the process.

 

[Tomfh]

Like the type of thing used for repairing structural cracks?

Yes you can use chemicals like that. I’ve used chemical anchor adhesive a few times when the gap is wide enough to fit the nozzle.

Alternatively a fluid cement grout like Dik mentioned, pumped into the gap.

A lot depends on the specific details.

 

[Ben29]

Here is the picture of the underpin. Do you think I need to drill the holes and inject it with grout? per PEinc's recommendations? Or do you think it looks tight enough?

 

[phamENG]

Well, there's a gap, so I'm not sure tight is a word that would even come into the discussion...

 

[MTNClimber]

Tough to tell since the x-ray filter wasn't turned on when the photo was taken. You may have full contact at the face but a void behind it.

Also, PEinc is a seasoned expert in shoring and underpinning. If he said jump, I would ask how high.

 

[SwinnyGG]

You have no way to know what kind of real underpinning you have.

Punching holes is the minimum level of investigation you're going to need; if this happened on my site the subcontractor would be paying for it too.

 

[JedClampett]

There's much better underpinners on this forum than me (PEInc), but I would insert steel wedge shims until they're tight, then put in nonshrink grout.

 

[Ben29]

I sketched these details to envision what PEInc is suggesting. Am I understanding this correctly? What if the void is located between the (2) 3/4" drilled holes?

 

[bookowski]

In my area the code has specific provisions for underpinning "Pit-piers shall be preloaded by wedging, use of permanent jacks, or by other means designed by the engineer". Typical in may area is wedging (pounding shims to refusal). If you're trying to preload then you'd need to do more than get grout in there.

 

[PEinc]

In Ben29's photo, it looks like the "drypack" was poured as a liquid grout rather than rammed or packed into place and that it does not extend across the full width of the underpinning pier. Where the "drypack" does not look like it is in place across the full pier width, can you clean out space to properly dry pack the ungrouted area? The pier to the right, near the piece of plywood, also looks like there is a gap between the top of the underpinning pier and the bottom of the existing wall footing. Again, what did the inspector inspect?

http://www.PeirceEngineering.com

 

[Ben29]

The circled area of my photo above shows how the concrete was poured up to the underside of the footing. There is no drypacking in this photo.

The photo below was taken after they "DRYPACKED", but I know they didn't rout out the top of the underpin as needed to actually pack the grout in there. I think they just smeared it over the outside of the pin to make it "appear" correct.

The underpin to the right of the pin in question was poured after the inspector pointed out that they need to leave space to properly drypack. And this pin was not yet drypacked at the time the photo above was taken. Oddly enough, in the photo below, this pin is not apparent. But I think this is just an optical illusion.