Bridges v Tunnels.

[David Paste]

Which is the better choice, in general, for:

1. Initial building costs.
2. longevity.
3. Ongoing manitenance costs.

I assume (yeah yeah) that bridges for 1, tunnels for 2, and I've no idea about 3 but would think tunnels.

I'm only wondering because Norway seems to enjoy digging tunnels to link their islands, over bridges. I had the thought that because bridges are subject to adverse conditions they would have a much shorter service life, whilst depending on the rock or what-have-you that a tunnel is driven through, it would last much longer, despite having a higher initial construction cost.

Also, I was looking at google maps and wondering how feasible a tunnel between Holyhead and Dublin would be compared to a bridge. I can't imagine a bridge would be a good idea at all.

[Jock]

Varies quite a bit with the individual situation.

Not necessarily, particularly where the bridge is over a very large drop and the tunnel is in where it is easy to tunnel.

Mostly, but not always.

Again, it depends on how the bridge is done.

Again, that depends on how the bridge is done.

Again, it depends on the nature of the under water ground.

[newshound]

The devil is in the detail. For the Oresund, there is a bridge and a tunnel for different parts of the crossing.

For Holyhead to Dublin to make sense you would also need to get rid of the bottleneck at the Menai Straits. Quite apart from trying to decide where to put the Customs point.

[alan_m]

And the tunnel. I watched a documentary a few moths back where in they built concrete tunnel sections o land, floated them out to the location where they were sunk and joined and then pumped out.

[HVS]

[Marland]

Those adverse conditions can affect the road or railway on a bridge as well, Norway being a country prone to snow using a tunnel keeps the link clear of snow,Ice and wind that could disrupt it.

Proposed in Spring last year with a bit of a fanfare by Boris and Co and then dropped quietly in the Autumn when having likely paid some friends ,sorry Consultants a load of dosh to confirm what people had said for free in the first place that it would cost to much to justify. The traffic isn?t really there to pay on the investment and is less now that many more ferry routes have opened direct between Ireland and the Continent since Brexit to avoid the hassle of going across the land bridge route across a non member state. For some thats a loss of trade servicing the trucks and drivers and less traffic for the English Channel Ferries. On the balance it less wear and tear on UK highways ,fewer emissions and fewer trucks to get stuck behind.

GH

[David]

Isn't there a deep trench between Britain and Ireland allegedly filled with dumped munitions?

Also, didn't one plan use the Isle of Man as a roundabout?

Blue sky thinking at its best.

Cheers

Dave R

[Harry Bloomfield Esq]

alan_m has brought this to us :

In the USA?

[Harry Bloomfield Esq]

David laid this down on his screen :

Yep, WWII surplus munitions were dumped there.

[Steve Walker]

Also done in Wales (A55 at Conway/Conwy), but not until the 1990s.

[The Natural Philosopher]

The bridge and tunnel that links Denmark to Sweden is done that way I believe, because the sea is shallow and they simply laid a tube on the sea bed, more or less which had no impact on sea traffic at all. In the bits too shallow for navigation its just a causeway on posts so to speak.

[charles]

That's how the North Wales Expressway gets under the River Conwy estuary

[Clive Arthur]

I think the Norwegians have a sense of national pride in their tunnelling skills. The impression I formed was that they're all blasted and they sneer at TBMs. There's a car park in Bergen - it may not be unusual - but it's underground, IIRC seven stories deep, and in rock.

Mind you, they have loadsa money.

[charles]

The last time we were in Amsterdam, they were building carv park UNDER one of the canals

[David Paste]

Currently the nearest one is just off junction 9 of the M56, so that's, err, great.

[David Paste]

Yeah, fascinating, that one. Big flexible teflon seals or something. Had to take seismic activity into account. I'll explore that link, thanks.

[David Paste]

This is what got me thinking about it - they have the money to tunnel so perhaps it's a cheaper in the long run.

[Andrew]

But not a tunnel. That is where millions of tons of ordnance was dumped after 1945. And I believe it is rather tougher material then that nice easy chalk marl that the Chunnel went through.