Strength of Existing Stone Masonry

[HeavyCivil]

I'm headed out this morning to measure an existing entrance slab to a Town Hall building. Bellow it is a "basement" but its really more of a vault that was used until the 60's as a drunk tank and then until the 80's as an embalming station - spooky.

We're designing the suspended entrance slab, concrete steps etc. The town does not want to fill in this vault but also does not want to replace the stone frost/basement walls that support the slab. Looks like its in great shape (see pic). So clearly its under light axial loading and some lateral earth pressure.

Its been there since the turn of the century with no apparent problems - still, on a 6 figure job it seems prudent to remove and replace - if not for resistance to implied loads for a clean connection with the new slab and stair wing walls.

Does anyone know of any good procedures or articles for the evaluation of existing stone masonry? Opinions welcome.

 

[Ron]

Core it and do petrography and unconfined compressive strength.

 

[HeavyCivil]

And for lateral earth pressure just take f't= 4x SQRT(f'c)and assume equal compression and tension blocks? Not sure if you can analyze flexure like that but its the only way I can think of without any steel.

 

[bridgebuster]

I agree with Ron. I working on the rehab of a century-old switch-back stair. The walls are granite blocks. We did the same thing - cored the walls and had a geotech look at the samples.