Slab load on buried pipe
Slab load on buried pipe
(OP)
I have a building that will have new mech air ducts running under the slab. They are 3' in diameter made of PVC (schedule 40). The bottom of the ducts will be 8' below finished floor. I am concerned about the weight of the slab and the slab loads applying pressure to the pipes. I have found equations(Boussinesq) that seem to be based more on footing loads being applied to underground pipe than slabs on grade. Anyone dealt with this situation before?





RE: Slab load on buried pipe
RE: Slab load on buried pipe
I took an equivalent soil height of H=5'+122.5psf/120pcf=6.1ft. I have found in AASHTO a formula for the load on a buried pipe, We=FexwxBxH, I got We=1.2x120x3'x6.1'=2636 lb/ft of pipe. This seems pretty conservative. I am trying to contact the pipe mfr. to see if they have any information on what soil loads their pipe can take, else I will have figure out how to calculate that myself. My slab loads seem to be minor in comparison to the soil itself. The mech. eng. specified this depth of embedment without considering the pipe strength.
RE: Slab load on buried pipe
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RE: Slab load on buried pipe
Remember that the soil pressure acts around the entire pipe - not just on top. The pressure isn't uniforn; hence the need to look at a design guide for buried flexible pipes.
Given that the soil load is significantly greater than the floor load, I expect that you will find that the pipe will be okay.
RE: Slab load on buried pipe
RE: Slab load on buried pipe
RE: Slab load on buried pipe
RE: Slab load on buried pipe
If your pipe runs are long and the cost becomes a problem, fill to a depth of two to three feet, then compact on top of the lean concrete after 72 hours. You - and the contractor - get a lot of benefits to this approach: peace of mind, pipe is permanently protected, and contractor has a firm base to compact against.
You can also use a cement stabilized sand - if locally available, although this isn't quite as advantageous as the lean concrete.
By the way, what is this for?
RE: Slab load on buried pipe
http://www.ipexinc.com/us_download/index.htm
Any suggestions on specifying a minimum cover on the pipes? I just don't want the slab sitting directly on top of the pipe itself.
RE: Slab load on buried pipe
http://www.ipexinc.com/download/pdf/Series_Pipe.pdf
RE: Slab load on buried pipe
I'd also suggest you use o-ring couplings on your pipe -
RE: Slab load on buried pipe
RE: Slab load on buried pipe
RE: Slab load on buried pipe
RE: Slab load on buried pipe
RE: Slab load on buried pipe