Spread footing above Sewer/Sanitary Pipe 1

[karimom]

Hi,

I have a project where I had a small spread footing for a mezzanine. During scanning/reviewing the existing conditions, we found a PVC storm pipe 3' below (its around 12" in diameter). I was just wondering the best practices on handling this from a design standpoint that isn't going to break the bank for the client. If I was designing from scratch I would be sleeving the pipe w/ a steel pipe.


I attached a picture for clarification

 

[SteynvW]

You could encase the pipe in concrete.

 

[civeng80]

Its no so much the PVC pipe that could be a problem but the backfill. The backfill spoil may just have been dumped back in the trench without compaction. The allowable bearing pressure over the trench would effectively be zero.

 

[LittleInch]

Either make your footing twice as wide or lay a concrete slab approx 3 feet wide over the top of the drain above where the footing is going

If you wanted to be really cautious dig out directly over the pipe area, backfill with something compressible, then slab over that like a subterrranean bridge.

Or if the backfill is pretty compacted just build over it - PVC isn't that delicate. 3 feet down is a good distance to not have an issue for bearing loads above it.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Liam Nesson]

You could still sleeve it. Fab 2 semi circle sections of pipe and bolt them (or weld) around the pipe. Pour some flowable fill under the sleeve instead of compacted sand. If you dont need future access to the pipe, concrete encasing might be the cheapest option.

 

[oldestguy]

Per LittleInch look up articles by two old Iowa engineers (Spangler was one)with what is called the imperfect trench.