Seawalls

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Seawalls

Postby MDavies » Thu Oct 01, 2009 11:55 am

Hello,
I'm new to this group...
I'm researching the use of dry stone walling techniques in the construction of seawalls.
Please let me know of any examples of good walls, of failures, of construction techniques, etc.
My particular interest right now are smaller walls (less than 6 ft high) that have been used along promenades in sheltered bays and harbours. Main interest is walls built with fairly random size and shape stone as compared to those types of stone walls where a perfectly smooth, tight-jointed face is obtained through stone cutting and fitting.


Any and all comments appreciated.
Thanks
Mike
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Re: Seawalls

Postby jim scott » Thu Oct 01, 2009 7:05 pm

Hi,I don't know how far your research will take you,but there is a fine example of drystone techniques,at the pier/harbour at Easdale,on the Isle of Seil,near Oban,where the long flat bedded stone or slate,is built vertically,where the stones above are placed with their points into the gap between the stones below,where they acted as wedges,tightening the ones below.
The other reason they were placed vertically, was that the wave action,had no flat area, to get purchase on, to lift the stones

I don't know how long this structure has been built,but it was built originally,for loading slate from the local quarries,so my guess is 100 plus years and maybe more and is still in good condition,

Jim
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Re: Seawalls

Postby George Gunn » Thu Oct 01, 2009 10:35 pm

I would imagine that if they are not laid as Jim says then they would at least be laid lengthways into the wall.
It depends on the wave action/pressure on it.
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Re: Seawalls

Postby MDavies » Thu Oct 01, 2009 11:46 pm

Jim,
Thanks for the reply - I quickly "google earthed" Easdale and found this photo: http://www.panoramio.com/photo/15494942
Is that the wall you're talking about?

Thanks
Mike
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Re: Seawalls

Postby jim scott » Fri Oct 02, 2009 6:48 pm

Here's a link to the slate pier,click on the third picture
http://canmore.rcahms.gov.uk/en/site/11 ... late+pier/
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Re: Seawalls

Postby jim scott » Fri Oct 02, 2009 8:20 pm

[quote="vikingdyking"]I would imagine that if they are not laid as Jim says then they would at least be laid lengthways into the wall.
It depends on the wave action/pressure on it.[/quote

Hi vikingdyking Even if they were laid flat,they would have to be laid on their edge,to create the least resistance to the wave action,as some of those slates /stones,are 3 to 4ft wide,

Jim.
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Re: Seawalls

Postby donald » Fri Oct 02, 2009 9:01 pm

The greatest harbour builder was Stevenson,as a lesser part of his constructions,
he built a pier in Wick bay which failed,which VIKING WALLER may tell you about ,but built another, which was successful, he built numerous sea walls around UK , road and rail bridges,but sources of info or about his achievements in sea walls are scarce
he pioneered seawall construction,look up the east coast of scotland from the Firth of Forth to Caithness ,and others you may be interested in is scottish lighthouse construction, which is amazing in its determination and ingenuity.
Will post links later,

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Re: Seawalls

Postby donald » Sat Oct 03, 2009 9:01 pm

http://www.nlb.org.uk/historical/stevenson.htm
http://www.bellrock.org.uk/stevensons/
ttp://en.wikipedia.org/wiki/Robert_Stev ... l_engineer)The Stevenson harbours I have seen have the building stones at an angle or vertical, so the hydraulic action of the pressure of the waves does not have an upward force.
more info to follow
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Re: Seawalls

Postby George Gunn » Sat Oct 24, 2009 8:45 pm

Nice pics Jim.
All the smaller, old surviving harbours in my area are built with stone on edge.
They were built by James Bremner.

He built harbours that lasted.

Pics here http://her.highland.gov.uk/SingleResult ... ='MHG1393'

The slots you see in the entrance to the harbour were used for wooden dams which would keep water in over low tide so the boats loading flagstone were still afloat.

Lots of pics on Google Images for other similarly built harbours around the Pentland Firth -

Keiss

Castlehill
Ham

There is a book about James Bremner who built them and also raised wrecks no-one else could .I think it is called " James Bremner - Wreck Raiser "

Not available on Amazon amazon at present but linky here - http://www.amazon.co.uk/s/ref=nb_ss?url ... eck+raiser

Hope this is interesting.
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Re: Seawalls

Postby Carole » Mon Oct 26, 2009 1:06 am

Hasn't Sean on here done a lot of this himself?

I'm sure I saw a fab pic he posted somewhere of a harbour wall.

found it;
http://www.dry-stone.co.uk/Pages/Dry_St ... orFull.jpg
He is a star 8) and here is where I got it from;

http://www.dry-stone.co.uk/
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Re: Seawalls

Postby stonewaller » Sat Nov 21, 2009 12:13 am

I resurrect this thread as I came across it when theorising about walls and floods in response to that new thread (I lost the post and am too tired to redo it) . It seems to have some relevance to walls and flooding which is after all walls and water action albeit of a different nature. Some good ideas and info I shall have to file away for future reference.

With regard to vertical stones in this type of wall, vg ideas. I'd like to add the poossibility that as with coping and cloddiau one advantage of vertical stones is the jamming/wedging you get, theoretically compared to a flat laid wall where stones are essentially held in place by the weight above them, here you also have forces acting from the sidesholdong the stone. It is possible therefore that the stones are more securely heldin place. (it gets a little complicated as the lateral forces may well diminish the vertical ones, if you remove a section, the section above may well not fall down ... but that's a little advanced and involved., and side-tracking).

As to Caroles post.. this one was actually a Garden wall in the Menai Straits and we cheated with a mortar core (the original had a lime mortar core and pointing - which had become somewhat degraded!).

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Re: Seawalls

Postby jerryg » Sat Nov 21, 2009 4:04 pm

Hi Sean, I was thinking about these walls with upright placed stones, you mentioned them in regard to the nigh on it might be possible after all curvy australian garden wall.
I have rebuilt plenty of walls at the sides of becks and the hardest thing seems to be to get the footings well enough dug in to stop them being undermined by the passing of water.
We tend to end up using the biggest stones we can find and hope that they don't move. When you have got nothing to use except rough flattish slates then this digging in becomes very difficult.
I see now the advantage of placing slates end on into the ground and forcing them together tightly with wedges. The water may still undermine them but will not be able to lift them. I think I shall try out this newly learned technique next time I have to mend one and see what happens.

I can imagine that if vikingdykings pictured Castlehill wall was built with the stone laid flat the water would have eaten its way underneath (or between) the slabs and the heavy wave action would have forced up the slabs. Whereas the wave action against these upright slabs would not cause this to happen.

Vikingdyking can we see a picture of how the Castlehill wallers have finished off the wall at either end?
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Re: Seawalls

Postby George Gunn » Sat Nov 21, 2009 11:58 pm

Photo link here - http://her.highland.gov.uk/SingleResult ... MHG1393%27

The massive upright slabs are on the exposed side of the harbour facing the notorious Pentland Firth and the Atlantic storms sending big waves from the North West.
I'll have a look at where the uprights finish near the harbour mouth and change to horizontal. Not easy to see without a boat . As far as I know the landward side backs into the shore.
I'll have a look tomorrow.
You will see from the attached photos that the top surface of the exposed pier has a vertical slab top, continuing to the top of the inside wall above the quay,to add weight and resist any lifting tendencies of the horizontal slabs below, on the inside of the high pier. The horizontal stones , even inside the pier, would be subjected to extreme air pressure through the pier due to very big surf breaking on the outside vertical face during winter storms.
The shorter pier on the landward side was damaged on the quay surface a good few years ago and was "repaired" with poured concrete 300mm thick. It was blown out even though it was not the worst weather side of the harbour.
Damage visible on nearest quay in this pic - http://her.highland.gov.uk/FullImage.as ... id=MHG1393
All the harbour walls sit on bedrock so there's no undermining possible.
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Re: Seawalls

Postby stonewaller » Sun Nov 22, 2009 10:42 pm

A haa,
Just returned from DSWA AGM even more tired but my whole lost threadwas about walls and water action in rivers etc where the wall falls down from the bottom up because the footings get undermined.... jerry some weird wavelength stuff going on here.

Anyway it was about a victorian dry stone canalised (and washed away) river system at plas newydd llangollen which I restored... there are some photos buried in the worksection of my website. Having previously had problems with similar walls here we dammed and pumped the river (in sections), escavated a deep trench, lined it with pvc and installed a pvc permeable drain (we couldn't prevent all the flow- some of it percolates through the gravel) filled it with quick setting cement to just below river bed. Then large boulders set on concrete and wall built off them. idea was it couldn't easily be undermined, and if it was a long section would have to be undermined before anything actually really happened ie the sections of wall in effect sat on a 20m+ 30cm deep, 1m wide foundation stone which wasn't really going anywhere. Thus far it seemsto be doing well... in a couple of places (where the rriver course itself hadto be re-excavated and thus the actual river bed level was a little dubious) the edge of the concrete footing is exposed.

Without getting to far into the heresy of using concrete in dry stone work (and I think I have previously nailed my colours to the mast in favour of concrete footings imitating bedrock) one plan the architect had was to build the whole with a mortared back, and except for one section I was able to convince them that the problem would be solely one of undercutting rather than stones being plucked from the face of (a well built - I hope) wall.

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Re: Seawalls

Postby George Gunn » Sun Nov 22, 2009 11:58 pm

Sean -Sorry if this thread has got away from the original post on sheltered water walls. Some things just flow that way ! :) But interesting.
JerryG -will report back on sea wall ends.
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