Cracked Concrete Basement Retaining Wall - New Interior Wall for Reinforcing

[DCEngr1]

Poured-Concrete Engineers:

Looking at an 8-foot high, 10-inch thick basement retaining wall that has sustained a horizontal crack for approximately 60 feet of its 123 foot length. Is it practical & feasible to remove the slab inside the wall, pour a footing, & pour a new wall to reinforce the existing cracked wall - tying the new wall to the existing wall. The existing wall has not moved differentially at the crack and has not sustained notable horizontal inward deflection. The existing wall is approximately 5 feet from and parallel to an existing street, making it more economical to leave the existing wall in place, avoiding serious distubance of the street.

Thank you for your assistance.

DCEngr1

 

[Signious]

Do you have any pictures of the crack?

Horizontal & at mid height on the compression face is weird for a retaining wall.

Given the cost of extensive repairs like like this, it might be prudent to scan the wall to see what kind of bar is installed then run the numbers to see if it works before getting too deep into the repair.

 

[hokie66]

DCEngr1,
If the existing wall has failed, your option is feasible. However, if the wall is reinforced, a crack may not mean that the wall has failed. I would be careful in excavating for a footing, as this presumably will increase the span on the existing wall. Perhaps do it in increments, similar to underpinning.

 

[racookpe1978]

123 foot is long for a basement wall. Commercial building?

If so, are there any odd or discontinuous loads that might affect the wall below?

 

[oldestguy]

Is this cold country? Looks like a typical result of frost heaving sideways fopr a basement wall with a load ion top. Any new design must overcome that push, which is significantly more than earth alone.

 

[XR250]

How on earth (no pun intended) are the out of plane loads on a wall of this length resolved by the floor diaphragm? Are there interior shearwalls?
If not, the wall may shoulda been a cantilever wall.

 

[jayrod12]

Maybe it's a combination of Signious and XR250.

Maybe the wall was designed as a cantilever which would mean a crack in the compression face, which is weird as Signious noted. So is it possible that for the 60ft of crack length, the wall has somehow changed support conditions from cantilever to pinned top causing the interior face to become in tension?

That would explain the location of the cracking, perhaps they didn't put any reinforcing on the inside face at all. It also wouldn't take much bending (inward deflection) to cause a visible crack.

Maybe I'm just throwing shit at the wall to see what sticks but it's oddly possible. Is there anything in the floor framing at the bounds of the cracks that could act as diaphragm supports laterally?

 

[Archie264]

A 123' long, 10" thick concrete basement wall sounds like a commercial building, as racook noted. Commercial basement walls are often designed as pinned-pinned walls, not as cantilevers, though that's possible too. But if it is a pinned wall then the horizontal crack at midspan is not too surprising, or at least not surprising in the context of that being the tension face. Hopefully it wasn't designed as a pinned wall and built as a cantilever wall, but that's not beyond the realm of feasibility. I once had a contractor do exactly that, as that was what he was accustomed to building but this was on a project that was small enough that it didn't make much difference.

In any case, I'd keep Hokie66's admonition in mind, that is, for excavation on the inside of the wall. If the excavation's on the outside of the wall then it wouldn't increase the load, unless I'm missing something.

 

[whh970]

Two quick thoughts that came to mind:
[ul]
[li]Lateral forces resulting from expansive soils could also be a factor. These forces can often be quite a bit higher than typical lateral soil pressures, and could act in a similar way to frost heave as mentioned by oldestguy. If expansive soils exist in that area, it might be worth looking into. Although if your username is any indication, I don't remember encountering expansive soils in the DC area (I used to work there).[/li]
[/ul]
[ul]
[li]I agree with Hokie66's concern about an increased span as a result of removing the interior slab, but I would be just as concerned (if not more) about removing that slab with respect to sliding resistance at the base of the wall. Especially considering that the equilibrium this wall has reached appears to match a pinned-pinned condition, I would expect the current load path for the lateral force at the bottom of the wall relies (at least partially) on the slab at base of the wall.[/li]
[/ul]