Hows a harbour wall built

[carlton]

I saw one being built in Ibiza about 25 years ago - Santa Eulalia or somewhere.

They just kept lobbing enormous rocks into the sea with a crane until they appeared above the surface. Course, this could be an example of fine Spanish engineering, but it appeared to work.

Just wondered, if they did that and then dropped a few hundred tonnes of concrete on the lot, wouldn't that work ?

 

[hlb]

With the exception of course, that they could breath whilst building the pyramids. Whilst lugging about large stones under water and not breathing, or seeing, is quite another matter.

 

[paulm299]

When they built Port Talbot Docks , They diverted the river, dug and faced the docks first and then diverted the river back into the dock .

 

[Deleted User YDKXO]

Absolutely definitely not /forums/images/graemlins/smile.gif

 

[Deleted User YDKXO]

Yeah but hlb said the harbour wall was brick built and straight sided so it definitely wasn't built by lobbing rocks into the water which is a modern method as we now have trucks and cranes that can handle large lumps. Actually it may sound crude but it's very scientific in that the shape and size of the rocks and the way they are put together is specifically designed. Often rocks are substituted with concrete dolos which actually lock together and are used where wave action is more severe

 

[hlb]

Lobbing stones in, is fine for outer harbour walls, cos ships dont moor on the outside. But the insides have to go straight down, at least below the depth drawn by the ships at low water.

Sorry about the bricks, I meant great big brick shaped stones.

It's a bit hard to take in, that divers sat in a bell thingy, till the next rock was lowered down, then swam out, found the rock and put it in place, in freezing water and hardly any vision.

Surely there are records around, that say just how they did do it.

 

[wp1234]

Don't know if this answers it but if you take the example of the Holyhead breakwater as a superb feat of engineering . Built 1845 - 1873 using 7,000,0000 tons of locally quarried rock and 2.5 km long - the longest breakwater in the UK Grade 2 star listed .
Essentially a slab sided structure built on a massive rock mound. All this without a JCB and readymix !!!

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[Firefly625]

What excellent pictures.... a massive feet of engineering....even today!

Surely that's the question answered! /forums/images/graemlins/smile.gif

 

[hlb]

No, it does not answer the question, cos it's a break water and not a harbour wall. It's very shallow by the wall, cos of all the rocks thrown in. I know cos I was there on Tuesday.

 

[Deleted User YDKXO]

You can't lay bricks or stone and bond them with mortar underwater (I've never met underwater brickies, has anyone else?) so the construction must have taken place in the dry so some kind of a coffer dam must have been temporarily constructed and the water pumped out. Second, steel wasn't around in those days so the idea of a steel caisson or steel sheetpiles is a non starter so that leaves timber to construct the coffer dam. Now timber piles have been around since the Romans so, for sure, somebody in 1600 would have known about the technique of driving timber piles into the sea bed to form a dam. Depending on the depth of water, it is likely that 2 or more rows of timber piles would be required and these rows of piles would be driven several feet apart and the gap filled with soil. If water still leaked through, the leaks could have been plugged with clay. Yes, continuous pumping would have been likely required to keep the coffer dam dry enough to work but pumps have been around since Archimedes, as already pointed out, so that technology was definitely available.

 

[wp1234]

[ QUOTE ]
No, it does not answer the question, cos it's a break water and not a harbour wall.

[/ QUOTE ]

How big a draft has your boat got - does it explain your speed question ? /forums/images/graemlins/laugh.gif

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Rig alongside the breakwater a couple of years ago

But seriously the Holyhead breakwater is Ok to come alongside on the landward side along most of its outer length but recommend you keep away at low water apart from outer most leg where you will be OK. You might have noticed some stone steps at points along its length to allow you up onto the structure from a boat.
The seaward side is deadly unless you really know it well so keep at least a 100 mts off it along its length .

 

[hlb]

It's about one metre deap near the harbour wall at low tide. I cant be bothered to get the chart out, if you want more accuracy.

 

[hlb]

Well I suppose some thing like that must have been the way, hard to think they could pump water out at the sort of rate required though.

 

[strakeryrius]

Quote:
You can't lay bricks or stone and bond them with mortar underwater

Actually the Romans had a form of concrete that would set or dry underwater; remember reading about it years ago.

Lots of info on this link
http://mediterranee.revues.org/index1952.html

 

[Deleted User YDKXO]

With 2 or 3 rows of piles filled in between with soil, particularly clay, there wouldn't be much leakage so the only pumping issue would be to get the water out initially and certainly they could have done that in the 1600's

 

[Deleted User YDKXO]

Yup, concrete is often poured under water but I've never seen a brickie or stonemason capable of laying bricks or stones underwater and even if there was such an animal, water erosion would take away the outer layer of the mortar. Anyway the kind of mortar used for bricklaying in those days would have been different from the concrete we use today and the concrete Romans used

 

[wp1234]

[ QUOTE ]
With 2 or 3 rows of piles filled in between with soil, particularly clay, there wouldn't be much leakage so the only pumping issue would be to get the water out initially and certainly they could have done that in the 1600's

[/ QUOTE ]
Yes this is the way they built the quay walls in Holyhead back in 1700/ 1800's .
Wooden panels/ piles knocked into the seabed ahead of the required quay wall then continuously pumped out like buggery behind them with hand pumps and buckets and a huge team of people .The large quay wall stones will have been cut and dressed ahead of the stone placement to speed up the stone lying operation. Health and Safety would have been a secondary issue back then of course.
Today with the advent of high tensile steels, superior compression fendering systems ,super plasticizers and the like there are very many other methods used to build berths .They may be cheaper and quicker to build but the longevity is questionable .

 

[geardownthreegreens]

Yep, i'm a brickie and i dont even like working when there's a threat of rain,let alone working under water ...... /forums/images/graemlins/grin.gif

 

[pheran]

[ QUOTE ]
..... so the only pumping issue would be to get the water out initially and certainly they could have done that in the 1600's

[/ QUOTE ]Pumping technology was extraordinarily well-developed by the 1600's and presented few problems - if you had a Dutchman on the team. Its one of the main reasons Holland exists today.