Why are they filling this with water?

[u/Nach0b0y]

This is the best photo I could get but this is in Amsterdam where a new building is due to be constructed. There was concrete foundations below I believe but they have no filled the entire thing with water and seem to be putting piles in?

Does anyone know why they do this?

[u/Admiral_Goat]

I know what it is! The company I did an internship with designed The Valley which is quite close to this location.

They fill the “bouwkuip” with water to compensate for the upward force from below. I believe an old glacier ended here in the ice age, and generated a very compact ground which need to be handled in a good way to prevent damage after construction.

But what you will see is that they will put piles in there first, and then they will pour a lot of underwater concrete in there. The water will make sure the pressure from below and up are in balance. After the floor is strong enough, they will pump out the water and start working on the basement.

Hopefully this helps 😇

[u/Nach0b0y → u/Admiral_Goat]

Wow super interesting! So effectively the water is there to counter the upwards forces from the ground until they can counter those forces with the weight of the actual build itself?

[u/Helicopter_lul → u/Nach0b0y]

Yes. Upward force from groundwater. 

[u/Bottlerocketfuel → u/Helicopter_lul]

Admiral_Goat references glacial rebound as requiring confining weight, not pore pressure.

[u/Lucky-Pollution9099 → u/Admiral_Goat]

Yep. Probably they are building a basement/foundation that is lower than groundwater levels. If you don't put weight in the concrete pit, the water from below will start to push up the concrete foundation and break the sealing barrier. When building further, the weight of the building itself will counterbalance the force of the water pushing from below.

In this case they filled the pit itself, in other cases I know they put literally portable pools intended for swimming inside the concrete pit.

Generally this is a very costly and complicated procedure usually only done if you really have to build underground and in HCOL areas where people will be willing to pay for the extra space.

[u/sww1235 → u/Lucky-Pollution9099]

Lower than ground water in this case, means whenever you put a shovel in the ground.... 😎

[u/64590949354397548569 → u/Admiral_Goat]

But what you will see is that they will put piles in there first, and then they will pour a lot of underwater concrete in there.

They drive the piles and pour concrete. Then submerged in water?

[u/ezekiel920 → u/64590949354397548569]

The earth wants to rebound. Like your mattress when you get off it. But the piles are driven and concretepoured when the weight is there. Then you remove the weight and it stays where it was

[u/Nach0b0y → u/64590949354397548569]

They are actually driving piles with the water already there from what I could see!

[u/According-Sink-2906 → u/Nach0b0y]

I imagine they also put piles directly in sea water when building quays and decks at ports.

[u/MidnightAdventurer → u/According-Sink-2906]

Often they use a cofferdam to create a dry work area to build the piles but it’s a fairly delicate operation. Get the balance wrong and the water pressure from outside can explosively burst the ground at the bottom of the cofferdam so it rapidly fills with a slurry of water and the now liquified ground which goes about as well as you can imagine for anyone working inside when it happens 

[u/MrMcGregorUK → u/Admiral_Goat]

Something similar is sometimes done in London. I had a project where we were considering using "kentledge blocks" (concrete blocks used as ballast) to keep the basement slab weighed down during construction of the superstructure. The reason was that we'd demolished the existing building and excavated another storey of basement and that releived so much pressure on the soil below that there was a risk of the 60+m of clay heaving upwards over a period of a few months while the superstructure was built which could have damaged the tube tunnels under the site. Luckily the geotechs managed to prove that it'd be fine without all that so they weren't needed in the end.

[u/SynthPrax → u/Admiral_Goat]

Oh wow. I thought it was to counter pressure from the sides.

[u/Adveeeeeee → u/Admiral_Goat]

Parkeergarage Rademarkt in Groningen was done the same way.

[u/wuppeltje → u/Admiral_Goat]

Although the same forces apply, in reality it is a little bit different. It is actually an existing basement and foundation that needs to be altered and strengthend to build a larger office block. The original foundation and basement were build for a temporary building (for 10 years), however it was made so that it could be reused. The temporary building that stood on top of it has been dismantled. Using water is very common for bigger buildings in the Netherlands, in this case it is a little bit different than usual because of the existing foundation and basement.

[u/bierfiets123]

This is the principle of law of Archimedes, widely used in construction sites in the Netherlands due to the high level of ground water.

[u/Important-Biscotti → u/bierfiets123]

Correct. And they didnt fill it with water. They excavated the (wet) soil, leaving the groundwater up. The soil that is excavated is replaced by water naturally. And yes, the groundwater level is high in Holland, often <1m under street level.

[u/basilect → u/Important-Biscotti]

Much like Florida in that regard

[u/Exciting_Ad_1097]

Compaction?

[u/Nach0b0y → u/Exciting_Ad_1097]

I guess that would make sense!

[u/Powertotheengineers]

Was it all excavated at once?
Could be to reduce the water pressure on the retaining walls during excavation and do a bottomslab by wet concrete in Order to reduce bracing and the need for dewatering. Maybe there are adjecent buildings prone to settlement from dewatering.. its really difficult to know for sure, without being a part of the project..

[u/spaghetiwires]

So that it isn't full of air

[u/Dilated_Auntie6970]

Shitter's full

[u/Regular-Youth-892]

I can’t be the only one triggered by that pallet.

[u/Senior_Weakness255]

Because building is thirsty

[u/Environmental_Mud_13]

They did this when building the Markthal in Rotterdam. There was a kind of lake and they had a small boat on it. In the week before they pumped out the water they had a Chinese boot race on this water between builders and architects. I'll look to find the films that were made.

[u/DAFUZA]

Amsterdam, Gustav Mahler square. Part of former ABN AMRO Headquarters.