Underground Mech'l Duct
Underground Mech'l Duct
(OP)
I have a job in Dallas, TX. Interior slab is on grade. Some how the architect has brewed up the idea of running mech'l duct work under the building footprint to AC the building. This building is very much like a storage warehouse in that there will be large vehicles driving around the slab-on-grade. I've designed a cast-in-place below grade trench to host the duct work and a thickened slab over the top that will support the vehicle loading. The contractor is wanting to get rid of the cast-in-place trench and simply bury the mech'l ducts underground. My concern with this is the slab loads + soil loads will crush the conduit.
Are there any design guides out there speaking to load distribution under a slab-on-grade vs. depth below grade?
Does anyone have alternative solutions to protecting below grade mech'l ducts?
Thanks for your help.
Are there any design guides out there speaking to load distribution under a slab-on-grade vs. depth below grade?
Does anyone have alternative solutions to protecting below grade mech'l ducts?
Thanks for your help.






RE: Underground Mech'l Duct
It's not that bad to use pipe, but I suspect it will shock them.
RE: Underground Mech'l Duct
BA
RE: Underground Mech'l Duct
RE: Underground Mech'l Duct
RE: Underground Mech'l Duct
I would guess that if you have slab on grade construction, the geotechnical engineer probably warned of at least 2"-3" of vertical slab movement due to expansive soils
I had a north-east architect try that on a west coast job once. After that suggestion, he wasn't the architect on that project for long.
RE: Underground Mech'l Duct
RE: Underground Mech'l Duct
The flowable fill would also serve as formwork for the slab above, however we are back to who is going to design the duct for flowable fill loading.
I am recommending using non-composite deck as formwork for the slab and suspending the ductwork. Perhaps add a sump pit for ponding water issues?
Thoughts?