cofferdam
cofferdam
(OP)
Hello all,
you guys do great work!
Contractor has lift station to place with in 60' of river. Water table at 4.9'. Very dense sand and gravel 50/4" at 5'and 15' remainder is 25-35 blow count sand/gravel with one clay layer at 20-23'.
Lift station 96" to be placed 19' deep.
any thoughts on alternative to sheetpile as not driveable through the hard layers.
Thank you.
Ted
you guys do great work!
Contractor has lift station to place with in 60' of river. Water table at 4.9'. Very dense sand and gravel 50/4" at 5'and 15' remainder is 25-35 blow count sand/gravel with one clay layer at 20-23'.
Lift station 96" to be placed 19' deep.
any thoughts on alternative to sheetpile as not driveable through the hard layers.
Thank you.
Ted





RE: cofferdam
RE: cofferdam
Only other thoughts have been to erect a caisson and dig from within to allow to drop with excavation, as it is not felt soldier pile walls could seal water well enough.
RE: cofferdam
RE: cofferdam
RE: cofferdam
There are risks: loss of ground, out-of-plumb installation, leaks. But these are things an experienced contractor can deal with. This is one hell of a lot cheaper than sheetpiling, grouting, dewatering, in-place improvement, etc.
Good luck!
RE: cofferdam
RE: cofferdam
PEInc- They may try soldier pile, will depend on river level, and their dewatering system.
Focht3- That was a thought of ours as well, but may be difficult to find that large of a diameter pipe in our area. When you talk about hydraulic excavation do you mean water jet?
DrDirt- I don't have a cost of that method, but think PEinc is correct that maybe to expensive in Montana.
geomo- Sheet pile manufacutres say they wouldn't even try to drive 1" thick pile in this mat'l, although may utilize combination of all methods- sheetpile, that is excavated from within to allow to drop, and drive though soft material.
I'll let you know what happens.
thanks again
RE: cofferdam
RE: cofferdam
By hydraulically mining, I had in mind a combination of water jetting and air lifting.
Let us know what you do, what works - and what doesn't.
RE: cofferdam
RE: cofferdam
RE: cofferdam
And regarding the "sunk caisson" approach: surely trucking in 96-inch RCP would be a lot cheaper than open cut excavation, jet grouting, diaphragm walls, etc. Lots of truckers out of work; although diesel is "expensive" right now, the haul costs ought to be pretty low in comparison to mob/demob costs of the equipment needed to complete some of the other approaches you have been considering...