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Underwater Intake Structure
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Source：Internet Author：Unknow Pubdate：2008-03-24
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damengr11 (Civil/Environme)
20 Feb 08 18:17
I have kind of a unique problem. We are doing a feasibility study of constructing a new intake structure for a reservoir. However, the owner really doesn't want to have to drain the reservoir so that we can build the new intake structure (for various reasons). Does anyone have any experience with constructing new intake structures under 50-100 feet of water? If so, how'd you do it?
Thanks for your time!
civilperson (Structural)
20 Feb 08 18:22
Cofferdam the area to build in.
damengr11 (Civil/Environme)
20 Feb 08 18:41
Cofferdam that deep? I haven't seen one that deep. What do they use to construct oil rigs out in the ocean?
字串7
COEngineeer (Structural)
20 Feb 08 19:52
I dont have the experience but my old man owns a sea water intake construction company in asia. Typically what he does he uses a prefabricated steel intake head and lower it with a barge.
Check out his company to see pictures.
http://www.swijetty.com
Never, but never question engineer's judgement
COEngineeer (Structural)
20 Feb 08 19:53
it can also be precast concrete of course. Never, but never question engineer's judgement
JedClampett (Structural)
20 Feb 08 21:13
You drill a vertical access shaft. From there you drill horizontally under the sloped bank of the reservoir. From a barge, you have someone drill throught the bank into the horizonral access shaft. 字串8
Alternatively, you could precast a shaft on the shore with a bottom, float it to the correct spot and sink it at the location of you horizontal shaft. Then either excavate with a clamshell or drill until you meet the horizontal.
I'd be worried about the water quality unless you have intakes at several levels.
msquared48 (Structural)
20 Feb 08 21:22
I assume from your post you have a 50 foot drawdown during the winter?
The only way I see is cofferdamming the opening. How would precast work in a rock opening for the inlet structure - and the face would have to be scaled too for bond and stability - Underwater? Needs to be dried - vertical beam-columns with struts to the hillside as required and sheeting to close - should be able to do this.
Mike McCann
McCann Engineering
Ussuri (Civil/Environme)
21 Feb 08 3:52
字串5
Quote:What do they use to construct oil rigs out in the ocean?
Well for ones that sit on the bottom, in shallow water up to say 200m, if steel, they are fabricated on land typically on their side then loaded onto a barge floated out to location and then up ended. If concrete (Condeep type), they are typically fabricated in a large dry dock then floated out to position and 'sunk' into place.
BarryEng (Civil/Environme)
21 Feb 08 18:17
To damengr11
I have the same problem. We have a dam that is 50 m deep with an existing control tower (wet tower with an internal operating gate). The control tower does not have an access bridge (it was used as an irrigation dam only). The utility wants to use the water for 'normal' water supply & requires to drain the dam over 2 years to allow the construction of a new intake tower (with multiple intakes for water supply), but in the two years req'd to drain, they want to take 'run of river' water to a WTW (from the upper levels of the storage). 字串8
One proposal we are looking at, is to remove the trash rack (using divers of course), & place a transition piece in its place & then connect on a 1000 mm PE pipe. This pipe will be terminated with a 'strainer' & will be located (tethered) with a float & anchors.
One of the original suggestions was to use a caisson & construct the intake within the structure. We probably will be using the existing infrastructure (different to your problem) & I will be very interested to see what other suggestions you receive to your problem.
Prepakt1 (Coastal)
21 Feb 08 21:41
It should be possible to pour a concrete intake underwater.
You need to make a steel mesh formwork and then fill if by pouring concrete into fabriform bags which will fill the formwork forming the shape of the steel mesh. Intrusion Prepakt /marineconcrete.com
bimr (Civil/Environme)
21 Feb 08 22:33
字串7
Why do you have to build under 50 feet of water?
If you have no boats in the reservoir, you can use a floating intake.
Otherwise you should follow COEngineeer's tip. Microtunnel from the embankment to the location of the intake. Then install a prefabricated intake using divers.
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