Precast Manhole to Footing Connection
Precast Manhole to Footing Connection
(OP)
I want to get an idea of what others do in this situation.
I have a 25 foot deep (10' ID) precast manhole. We are going to put "doghouses" in the bottom so that it can be placed directly over some existing 30" and 36" pipe. A footing will be poured beneath the existing pipe and the manhole will then be set.
My question:
How do others go about attaching the precast manhole to the cast-in-place footing??
Additional:
We are thinking about "flooding" the manhole so we can neglect bouyancy. Does this change how you attach the two elements??
I have details I use when it's all new (nothing to work around) but this is a little different than what I've done before. THX
I have a 25 foot deep (10' ID) precast manhole. We are going to put "doghouses" in the bottom so that it can be placed directly over some existing 30" and 36" pipe. A footing will be poured beneath the existing pipe and the manhole will then be set.
My question:
How do others go about attaching the precast manhole to the cast-in-place footing??
Additional:
We are thinking about "flooding" the manhole so we can neglect bouyancy. Does this change how you attach the two elements??
I have details I use when it's all new (nothing to work around) but this is a little different than what I've done before. THX






RE: Precast Manhole to Footing Connection
I have encountered this situation once before. With your situation it will actually work even better because you have an extremely deep manhole of a large diameter.
When casting the bottom of the manhole, allow for a keyway in the top surface. Placing a compressible, watertight gasket in the keyway will create an excellent seal. The selfweight of the manhole alone will create a uniform and watertight seal around the entire perimeter. The keyway will also keep the manhole laterally stable on its base. It works quite well and its relatively inexpensive.
Good Luck.
RE: Precast Manhole to Footing Connection
I've always poured concrete up around the bottom of the barrel section (bottom foot or so) but this situation doesn't lend itself to that very well.
Thanks for the response!!
RE: Precast Manhole to Footing Connection
On my project, I used a 16" thick bottom slab with a 4" key. I've also seen different key shapes: \_/ or |_|
I always prefer to use the first one if possible. Cheers.
RE: Precast Manhole to Footing Connection
RE: Precast Manhole to Footing Connection