Building demolition and common basement wall

[jdbpe]

I have a project with two old buildings (two stories) that share a common basement wall that consists of 20 inch thick stone rubble. The building to remain has a basement slab 12 feet below the first floor. The building to be demolished has a basement slab 8 feet below the first floor.
Our demo spec calls for removing the basement slab (higher slab) and three other perimeter walls of building and backfilling this area eith controlled fill. The common wall that will remain will now function as a retaining wall for the basement to remain.
Cores on the wall revealed that this wall could not function as a retaining wall.
How do we reinforce this wall? There are not any plans for future use of this lot that would allow us to design this wall, i.e. two story with steel columns and footings, load bearing etc and requirements for underpinning etc.
Do we require the contractor to drive sheet piling several feet from the wall and leave it up to the new owner to remove and build/reinforce as needed. Thanks

 

[oldestguy]

Check your local and state statutes.

In some areas the owner of a property has to protect himself against problems with excavation or filling next to his property line, sometimes with a limit for the exavation depth so involved.

I've been on a case where filling next to the property line caused damage beyond it, but it was not considered the fault of the guy doing the filling, on the basis of that law.

 

[oldestguy]

I figured you would have more response by now.

Anyhow, as I think about this, if there is sufficient building weight on that wall, to keep any part of it from going into "tension" because of the new earth load, then nothing would need to be done. I liken this to a stack of kids blocks. Put a compression load on that stack and it resists lateral loads pretty ewll. Same principle apples if this was concrete block.

However, a form of security could be done easily by installing tie-rods,anchored in the "inside" with a plate, and extnding into the fill. You can do all sorts of things there, such as attaching to dead-men, etc. as the fill is placed.

This would be a whole lot easier than using sheet piles and cheaper.

Any good local geotech ought to be able to calculate the general dimensions of what you need. The design is something like a reinforced earth wall situation.

I suppose galvanized material would be more permanent.

 

[PEinc]

Check the common foundation wall against the other walls of the remaining building. I doubt that the common wall was built differently. If the common wall was constructed the same as the other walls of the remaining building, you may be OK.

 

[oldestguy]

I forgot to mention one thing that may be useful.

I once had the opportunity to check pressures impinged on a 50 ft. high non-yielding building wall that was to have sand fill placed against it. The wall was designed for an equivalent fluid pressure of 35 p/cf. As the fill was raised up in compacted layers it became apparent that this design was being exceeded. In one case a compactor passed by the site 12 ft. above the sensor next to the wall and the pressure raised somewhat there (12 feet below it).

We resolved the situation by calling for compactors to stay 24 inches away from the wall. That worked very well and no setlement resulted. The silo effect hang up of loose soil caused this result. Only active pressure developed.

So, keep the compactors 2 ft. from your wall and it is expected that active pressure will occur.