Build Pile Cap In High water area, under Active Airport terminal
Build Pile Cap In High water area, under Active Airport terminal
(OP)
Does anyone have a way of stopping water intrusion into a pile cap while I excavate, chip piles down, set the rebar mats, and then place concrete in a pile cap. Other than well point. Multiple pile caps but, the largest is about 15'x13'. Here are the tricky parts.
1. Under an active airport terminal, with the closest daylight area about 500' away.
2. Soil is contaminated and thus the water smells like old jet fuel.
3. Encounter ground water at approximatly 2' into the excavation, going 4' deep.
1. Under an active airport terminal, with the closest daylight area about 500' away.
2. Soil is contaminated and thus the water smells like old jet fuel.
3. Encounter ground water at approximatly 2' into the excavation, going 4' deep.





RE: Build Pile Cap In High water area, under Active Airport terminal
What type and how permiable is soil?
How much headroom?
RE: Build Pile Cap In High water area, under Active Airport terminal
RE: Build Pile Cap In High water area, under Active Airport terminal
Civilperson, good advice but, not an option.
RE: Build Pile Cap In High water area, under Active Airport terminal
RE: Build Pile Cap In High water area, under Active Airport terminal
RE: Build Pile Cap In High water area, under Active Airport terminal
Well, not the first time, but always fun.
I hope you're using a local geotech, but it doesn't sound like it.
Tremie will save you dough by allowing you to work wet,
but the inspection requirements and capping details may not allow it.
If dewatering is required, consider constructing a sheetpile coffer dam, overexcavating,
and pouring a tremie seal following pile installation (auger cast?).
That will reduce the dewater volume significantly.
Get a package water treatment system to handle the effluent, and pump it right back into the ground.
You will likely need a SFWMD/DEP permit for that (2 to 6 weeks). Get it, you don't want to be shut down in flagrante.
I suspect the budget will experience a bit of strain.
RE: Build Pile Cap In High water area, under Active Airport terminal
Live with the water and look toward tremie placement of concrete even if you add several feet of "filler or sealer" concrete under the real pile cap. Rough excavation is much cheaper than total dewatering.
RE: Build Pile Cap In High water area, under Active Airport terminal
RE: Build Pile Cap In High water area, under Active Airport terminal
RE: Build Pile Cap In High water area, under Active Airport terminal
12 feet of headroom is not bad. I see two possible options or a combination of both.
1.) Drive sheets to effect a cut off dam. For a four foot cut heavy sheets will not be needed and the top 2 feet could be pushed back to further reduce the height. Light wt sheeting can be driven by handheld breakers or pressed by jacking against the overhead if it is strut. adequate. The sheeting will significantly reduce pumping requirements.
2.) use precastpile caps that fit over the piles and attach mechanicallyor are grouted in place. This has been done on limted access projects.
RE: Build Pile Cap In High water area, under Active Airport terminal
RE: Build Pile Cap In High water area, under Active Airport terminal
Escrowe, I was already thinking along the same lines as you but, that's quite an expense and what if it doesn't keep the water out? FYI, no one forgot dewatering, yes a local geotech, and we apply today for the dewatering permit. The work is down the road a few months.
concretemasonry, thanks for the info
Big H, augercast already installed
hokie66, pile cap to support a new elevator pit. we are to excavate about 12 feet down to include a sump pit.
DRC1, your idea 1 will be helpful, idea 2, I forgot to tell you it's an elevator pit/pile cap
RE: Build Pile Cap In High water area, under Active Airport terminal
but they come with the territory.
If the excavation is properly sealed, and the sheet pile
properly installed, you should be able to work 'in the dry'
with minimal pumping.
That should satisfy the inspection requirements.
Unfortunately, construction of a tremie concrete seal
will require overexcavation to a bottom depth
at least twice the depth below groundwater of the top of the seal...
...unless some other means than dead weight is employed
to resist hydrostatic pressure/bouyancy.
And of course the top of the seal will have to be set
below the planned bottom of the pile cap.
That's a lot of digging.
Have you considered perm-grouting the perimeter of the excavation area?
That could significantly decrease permeability
and lateral loads on the excavation support system.
It could also be possible to injection-grout an excavation
floor, and pour a relatively thin mat
instead of a full-depth seal.
I would suggest checking in with Hayward Baker or similar.
Of course the expense of grouting may approach
that of a tremie seal.
RE: Build Pile Cap In High water area, under Active Airport terminal
RE: Build Pile Cap In High water area, under Active Airport terminal
and it sounds like something needs to be done...
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RE: Build Pile Cap In High water area, under Active Airport terminal
RE: Build Pile Cap In High water area, under Active Airport terminal
RE: Build Pile Cap In High water area, under Active Airport terminal
Thanks everyone, I'm going to over excavate and concrete the bottom about two feet and the slope the sides about 45 degrees and concrete. Basically build a swimming pool with 45 degree sides and try to keep the water to a managable level so they can cut and chip the piles, set the mats, dowels and forms. I can get the inspections and pour the pile cap/bottom of elevator pit. Then I should be out enough to form the walls of the pit.
Thanks again for everyones advice. This was the first time I used this forum. Extreamly easy and helpful
RE: Build Pile Cap In High water area, under Active Airport terminal
watch out for the pitchfork waving, torch bearing townfolk...
RE: Build Pile Cap In High water area, under Active Airport terminal
RE: Build Pile Cap In High water area, under Active Airport terminal