Need clarification on definition of "Caissons"!!! HELP!

[nutbutter]

Hiya,

I don't know how I missed getting a full grasp on this in undergrad.

Obviously, I've googled/wiki'd and done some research online. My online research leads me to believe that this is some huge structure that allows people to enter and dig out the soil below.

My problem is that the online definitions and what I hear being used in the industry don't jive. I hear people talking about using caissons on commercial building projects. I'm positive that people aren't entering a subterranean structure on commercial projects to dig out a foundation!! So where's the bust??

Can someone explain to me the actual meaning of caisson? And is there an alternate meaning that doesn't involve an underground structure to allow for excavation? When hearing it in context it almost sounds synonymous with some type of pile.

Help me not sounds like an idiot! Peace,

N. Butter

 

[msquared48]

In the "Standard Handbook for Civil Engineers" by Meritt, you will find a definition and discussion of the subject on page 7-45.

Mike McCann
MMC Engineering

 

[RWF7437]

" I'm positive that people aren't entering a subterranean structure on commercial projects to dig out a foundation!! So where's the bust??"

The "bust" is that a caisson IS used for the specific purpose of allowing people to enter a subterranean space. Google IMAGES of caissons and you will find hundreds if examples.

 

[nutbutter]

Well, thanks Mike, but I don't have access to that book.

RWF, I understand that IS what a caisson is, but is there an alternate definition? Or do some people use the word loosely for some sort of cast-in-place pile or something?

I'm sure caisson work happens on commercial sites, however, the specific site I'm talking about had NO subterranean excavation and 2-3 people had mentioned caissons. Now, I'm not entirely familiar with the project, but I have no idea why caissons would be needed!!

Thanks for your responses guys! I guess I'll do a bit more research.

N. Butter

 

[RWF7437]

Encyclopedia > Caisson (military)

In military context, caisson is a carrier of artillery ammunition. Historically, artillery refers to any engine used for the discharge of projectiles during war. ... Boxes of ammunition clog a warehouse in Baghdad Ammunition is a generic military term meaning (the assembly of) a projectile and its propellant. ...


The song "The Caissons Go Rolling Along", written during the occupation of the Philippines by the United States of America refers to these; the version adopted as the United States Army's official song has, among other changes, replaced the word caissons with Army.

 

[nutbutter]

Hey guys,

Here's exactly what I'm talking about. I did an image search for caissons and one of the first pages that comes up has this as a definition for caisson:

>>>What is a Caisson?

Caissons are a deep foundation support that is constructed by placing fresh concrete and reinforcing steel into a drilled shaft. These reinforced concrete piles are cast in holes of predetermined diameters and depths drilled through soil and rock to the desired bearing stratum. The Large Diameter Drilling Group of Brayman has the capability and experience of drilling shafts from 18 inches to 96 inches (and larger) in diameter, and to depths of 150 feet.

Caissons, which are capable of supporting high, concentrated loads, are typically used to set piers for bridges, underpasses, structural supports, as well as in slide prevention applications. Caissons are viewed as a reliable, versatile, and economical foundation support solution.<<<<

Now, tell me that's not entirely different from what you read about on wikipedia, the subterranean structure with compressed air housing manual excavators. The definition above sounds like a drilled (CIP) pier to me!! Why do many people call these caissons?? There's no subterranean compartment to house excavators in this caisson.

Sorry for the confusion, but this has long bothered me. ANY clarification will help!

 

[nutbutter]

Here's the link to that site. There are people in the industry who appear to define caisson differently:

http://images.google.com/imgres?img...ev=/images?q=caissons&gbv=2&hl=en&safe=active

You'd think these guys would know what they're talking about as they are deep foundation specialists.

NB

 

[RWF7437]

If you want to know the meanings (plural) of a word look at all the ways it can be used...not just the first page that comes up.

Try "bolt" for example.

good luck

 

[nutbutter]

OK.

I understand the traditional meaning of caisson....the watertight structure that allows for subterranean excavation.

Does caisson also mean a drilled pier, because I'm seeing it all over the place.

Sorry if this is ridiculous, but it's a HUGE pet peeve of mine when people use incorrect terminology. SO, does caisson also mean "drilled pier" or "cast-in-place pile" or something to that effect.

Lord knows I'll never be working with caisson (definition 1). Those appear to be for projects that involve massive structures. Our projects are massive, but being WWTPs/WTPs, the structures aren't quite on the same scale. However, I guess we could get ourselves into a position where a caisson would be needed.

NB

 

[RWF7437]

One of the Water Treatment Plants for the City of Chicago was built about 1955 in Lake Michigan. It is built entirely on Caissons which were composed of driven steel sheet piles , dewatered, and filled with rock and concrete. I watched it being built from my classroom at Navy Pier, then the "campus" of the University of Illinois, Chicago.

Just one of the many ways caissons are built.

 

[Drumchaser]

nutbutter


"There are people in the industry who appear to define caisson differently"----I think this is a correct assessment.

One version that you described would be what we call soldier shafts constructed in a circle to stabilize an opening in the earth.

I have heard the word expressed as a large diameter pipe that allows workers to access a below grade top of drilled shaft elevation.

I thought the older gentlemen used to call these tires, probably not the same spelling.

Hope this helps

 

[jorton]

Around here, Georgia, we use the term caisson for what many would call a drilled pier/shaft. Many of the specialized trades develop their own jargon that may not make perfect sense to others. Maybe we call them caissons just to confuse non-bridge engineers .

 

[born2drill]

nutbutter,

Today, a caisson is a drilled shaft. The word has undergone something of a transformation as construction methods and equipment have improved.

In the old days, things were a lot more low-tech. They would sink a steel shell, usually by piling dead weight on top of it. Men would go down inside and hand excavate. It was slow, tedious, and dangerous work. For the building of the Brooklyn Bridge, I remember reading progress was something like 6" per week.

Nobody builds them like that anymore. Now we have fantastic drill rigs, vibro hammers, oscillators, rotators, and a host of other equipment and tools to do the same thing.

One other note - "Caisson" also has slight variations in meaning depending where you are in the country. For example, in NYC any drilled micropile (as small as 7" OD) is considered a caisson. Most, I think, use the word to refer to a larger diameter drilled shaft - say 18" and up.

 

[jorton]

Born2drill, good point. I would consider a caisson to be a shaft that is large enough to allow a person to inspect the bearing surface at the bottom of the shaft, say 36" and up.

 

[born2drill]

Well, with down-hole cameras it's no longer necessary to hoist a man down the shaft to inspect rock. So hole diameters too small for a person to physically fit into can also be considered caissons.

Another case of equipment progressing with the times and changing what a "caisson" is...

 

[BigH]

When I first started out a caisson was either (1) a drilled shaft or (2) a large concrete structure floated out and sunk for a wharf - among several other definitions. We have had threads on this in the past - might want to search. The main thing is that it means different things in different parts of the country (USA/Canada) and the world. Usually one would think that they are big enough to enter and work - like described in Chicago (GOW CAISSON) but typically now, I think, most use them as drilled shafts/bored piles/bored caissons, etc. The main thing when using the term is to ensure that you have provided the "adjectives" to clearly define what YOU mean by the term. In India, they - the big ones - are called Well Foundations.

 

[HamishMcTavish]

dictionary.com gives the following:
1. a structure used in underwater work, consisting of an airtight chamber, open at the bottom and containing air under sufficient pressure to exclude the water.
2. a boatlike structure used as a gate for a dock or the like.
3. Nautical. a. Also called camel, pontoon. a float for raising a sunken vessel, sunk beside the vessel, made fast to it, and then pumped out to make it buoyant.
b. a watertight structure built against a damaged area of a hull to render the hull watertight; cofferdam.
4. a two-wheeled wagon, used for carrying artillery ammunition.
5. an ammunition chest.
6. a wooden chest containing bombs or explosives, used formerly as a mine.
7. Architecture. coffer (def. 4).

My experience of them is in dockyards keeping water out of the docks whilst work is carried out.

Cheers, HM


No more things should be presumed to exist than are absolutely necessary - William of Occam

 

[DRC1]

Cassions were orginally dug in structures, generally box shaped, to form piers etc. The foundations of the brooklin bridge, as mentioned above, were cassions. Compressed air was used to keep ground water from entering the excvation.
Eventually Round shapes became more popular as a ring was a much more economical shape than a box and steel became readily available. Hand dug cassions are still used, but not as frequently. As born to drill dicussed, eventually drilled piers replaced habnd dug cassions for much of the work. But since the final product is still similar, the name has been attached to drilled piers. There is no right or wrong definition. This is true about many areas of heavy construction. Pile driving is rife with conflicting definitions.

 

[HgTX]

My experience with the term has been in reference to a drilled shaft of fairly large diameter (3 ft or more).

Hg

Eng-Tips policies: faq731-376

 

[chicopee]

Caosson is also a french word for box. Originally a caisson was a large box without bottom submerged for work to excavate muck and river bed material for constructing footings for piers.