Ancient bridges

[D.B. Cooper]

How were the foundations for bridges like these:
http://upload.wikimedia.org/wikipedi...3%BCcke.01.jpg
http://en.wikipedia.org/wiki/File:Bridge_Alcantara.JPG
http://upload.wikimedia.org/wikipedi...St._Angelo.jpg
Constructed without means for the workers to sustain themselves underwater? How did they do it?

I watched 30 seconds of a show called Ancient Inventions or something like that, basically they were testing a glass sphere that covered the head, so ancients could last underwater with an air bubble around them. But somehow I find this hard to believe.

[Spartacus the Irish]

I watched 30 seconds of a show called Ancient Inventions or something like that, basically they were testing a glass sphere that covered the head, so ancients could last underwater with an air bubble around them. But somehow I find this hard to believe.

Why? You put a vase or a pot upside down in some water, and you find that air is trapped inside it. Thus its not a giant leap to using that vase or pot as a stationary air reserve when you are working, popping your head in and out to prolong the amount of time you can spend on the river bed.

And I suppose were the river small enough you could divert the flow until the foundations were laid (though this is just a guess of mine).

[Encino_Man]

From what I know they would wait for the lowest tide in a river before building a bridge so as not to have to contest with a stronger current. At that time they would use a raft/pulley system that would float the rocks out to the prescribed spot where they would be settled down to create a pocket inside the stones while the water was diverted around the work site. <> Like that. Then using the Archimedes Screw they emptied the water out so that afterward men could begin laying the foundations of the bridge, which was preferably over bed rock. If not, they would use piles that were driven into the soft bottom until it was stable to start laying the foundations of the bridge.

The Roman Pile driver that would be floated out onto a river to drive in the piles:


The Archimedes Screw that was used to empty the water out:

[D.B. Cooper]

Why? You put a vase or a pot upside down in some water, and you find that air is trapped inside it. Thus its not a giant leap to using that vase or pot as a stationary air reserve when you are working, popping your head in and out to prolong the amount of time you can spend on the river bed.

And I suppose were the river small enough you could divert the flow until the foundations were laid (though this is just a guess of mine).

That's true, I just have a hard time picturing dozens of laborers working away on the river floor with jars on their heads.

From what I know they would wait for the lowest tide in a river before building a bridge so as not to have to contest with a stronger current. At that time they would use a raft/pulley system that would float the rocks out to the prescribed spot where they would be settled down to create a pocket inside the stones while the water was diverted around the work site. <> Like that. Then using the Archimedes Screw they emptied the water out so that afterward men could begin laying the foundations of the bridge, which was preferably over bed rock. If not, they would use piles that were driven into the soft bottom until it was stable to start laying the foundations of the bridge.

The Roman Pile driver that would be floated out onto a river to drive in the piles:
The Archimedes Screw that was used to empty the water out:

That is interesting, thanks.

[Blau&Gruen]

Constructed without means for the workers to sustain themselves underwater? How did they do it?

One technical solution for stone piers is to box out with boles the area around the future piers. If the bridge is built entirely with wooden elements then the constructors may ram boles directely into the river bed. Celtic and roman field bridges were obviousely made in that fashion. Stone bridges require either the method described above or a temporary redirection of the river at the construction site. If the river is not very broad, then a wooden bridge can also be constructed from both riverbanks as a suspended construction.

[Tiberius Tosi]

I had always heard that if the river could not be redirected, they would simply box off with (usually wooden) beams, the sections where they want the stone foundation under water to go. They would then drain those boxes, mostly likely with Archimedes' screw, and then workers could either be lowered in or more likely a temporary framework would be put around the entire building project so workers could simply walk into these squares and lay the stone foundation (which is technically below water level but they are in completely dry conditions because they are boxed in). This always made sense to me since even on the fancier design bridges, the portion of the stone beams that are under water are usually simple square shaped foundations.
Of course this is only with large stone supports, with wooden supports it's much easier. Basically stakes could just be driven into the riverbed. Sometimes I have heard that the entire flow of the river was redirected, but most of the rivers in which stone were needed probably were too long and big of rivers for this to have been the norm.

[Encino_Man]

I had always heard that if the river could not be redirected, they would simply box off with (usually wooden) beams, the sections where they want the stone foundation under water to go. They would then drain those boxes, mostly likely with Archimedes' screw, and then workers could either be lowered in or more likely a temporary framework would be put around the entire building project so workers could simply walk into these squares and lay the stone foundation (which is technically below water level but they are in completely dry conditions because they are boxed in). This always made sense to me since even on the fancier design bridges, the portion of the stone beams that are under water are usually simple square shaped foundations.
Of course this is only with large stone supports, with wooden supports it's much easier. Basically stakes could just be driven into the riverbed. Sometimes I have heard that the entire flow of the river was redirected, but most of the rivers in which stone were needed probably were too long and big of rivers for this to have been the norm.

I knew there were some things I was forgetting

@ davide.cool - Huh... I never really heard about Roman dams. Thanks for the info on them. Wish I had thought about those when I did an archaeology project on Rome last semester

[DAVIDE]

I knew there were some things I was forgetting

@ davide.cool - Huh... I never really heard about Roman dams. Thanks for the info on them. Wish I had thought about those when I did an archaeology project on Rome last semester

Romans built dams with the purpose to:

- redirect rivers to build bridges or new buildable areas

or

- collect drinkable waters forming artificial lakes

or

- protect towns against floodings

[DAVIDE]

Rivers were redirected to build the bridges

Harbaqa Roman dam, 365m long, 21m high

Spoiler Alert, click show to read: 

I had always heard that if the river could not be redirected, they would simply box off with (usually wooden) beams, the sections where they want the stone foundation under water to go. They would then drain those boxes, mostly likely with Archimedes' screw, and then workers could either be lowered in or more likely a temporary framework would be put around the entire building project so workers could simply walk into these squares and lay the stone foundation (which is technically below water level but they are in completely dry conditions because they are boxed in). This always made sense to me since even on the fancier design bridges, the portion of the stone beams that are under water are usually simple square shaped foundations.
Of course this is only with large stone supports, with wooden supports it's much easier. Basically stakes could just be driven into the riverbed. Sometimes I have heard that the entire flow of the river was redirected, but most of the rivers in which stone were needed probably were too long and big of rivers for this to have been the norm.

Archimede lever was used for wells, to drain waters from ship or small torrents. In case of rivers they were usual to build dams. Plus they used pozzolana lime which had cement idraulic properties


"there's a sort of sand that, naturally, has extraordinary qualities... if mixed with lime and caementa, become so hard underwater as in the ordinary structures"

- De Architectura


Roman dams in Ebro basin

La pared de los moros



Dam of Muel



Dam of Almonacid de la Cuba




Prosepina Dam






Carnalvo dam


[IMG]file:///C:/DOCUME%7E1/Davide/IMPOST%7E1/Temp/moz-screenshot-4.png[/IMG]


dam of Ituranduz
[IMG]file:///C:/DOCUME%7E1/Davide/IMPOST%7E1/Temp/moz-screenshot-5.png[/IMG]



Alcantarilla dam

[Encino_Man]

Oh no I figured as much but they just totally skipped my mind. The dry spots around them do make me wonder what that area was like before they built the dams tho. Thanks again

[Baron Thunder-ten-tronckh]

I am not sure on the historical accuracy, but oftentimes, historical fiction has grounding in truth - I know were I to write the stuff, the only historical divergence would be the plot - and so when I suggest the following, don't immediately denounce because it comes from fiction.

In Kevin Follet's World Without End, the protagonists drives wooden stakes into the river in a circle, and then another lot of stakes in a concentric circle around the first. Then, filling the gap with .... whatever, the water is then drained out by buckets.

[ivan_the_terrible]

I am not sure on the historical accuracy, but oftentimes, historical fiction has grounding in truth - I know were I to write the stuff, the only historical divergence would be the plot - and so when I suggest the following, don't immediately denounce because it comes from fiction.

In Kevin Follet's World Without End, the protagonists drives wooden stakes into the river in a circle, and then another lot of stakes in a concentric circle around the first. Then, filling the gap with .... whatever, the water is then drained out by buckets.

The danger with fiction texts is not so much deliberate falsification/divergence on the part of the author. It's that they quite often don't read widely enough, and often don't have the skills to research properly anyway. Depends on the author, of course.