Existing pipe below new slab on grade

[WWTEng]

Situation: Exist 8" water main, not in use anymore, invert level 5' below top of new proposed 5" SOG. The contractor is wondering if he can fill the pipe with concrete, cap it each end and leave it in place.

Personally I think at the given depth it should be OK. Concrete in the pipe will shrink a little but due to the depth of the pipe, any pressure from the slab can bridge around the pipe.

 

[hokie66]

Probably doesn't need to be grouted, but grouting won't hurt. What is the alternative? Digging a trench to take the pipe out just creates another excavated and filled area which could create more problems than leaving the pipe in place.

 

[msquared48]

I can't believe that the load from a 5" sog would crack an 8" water main 5 feet down, used or not. Seems like a lot of room for the load to the slab to spread out and dissipate. Save your money and move on.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[BobNeng]

Probably depends more on the overdig for the pipe than the pipe itself

 

[jnich]

What are the design loads on the SOG? What is material is the water main made from? Soil type?