Another new UK-Ireland speculative plan

[HSTEd]

So how exactly, with an extended tunnel, are you proposing to address the fumes produced by internal combustion engines? Before you say electric vehicles only please enlighten me as to the availability now or anytime soon of an electric HGV....
There were damned good and highly sensible reasons why the Channel Tunnel is rail only.

The Fehmarn Belt is managing it with a tunnel length of 18km, a handful of very large gravity base structure like systems could be employed as ventilation if required for longer tunnels

Ultimately the simple answer is you build a viaduct instead.

 

[zwk500]

Anybody suggesting a road route should read this: https://www.roads.org.uk/articles/euroroute

The channel road route involved 2x 5-mile bridges to reduce the tunnel length to a manageable level. The Channel is shallower, narrower and less badly affected by weather than the Irish sea.

 

[bspahh]

how expensive would building tunnels large enough to take double track be?

This briefing sheet from the ICE from December 2020 says on page 6

Costs would be much higher on the longer routes that avoid Beaufort’s Dyke. The estimated costs for a bored tunnel option for Route 2 would be £15bn, based on the Channel Tunnel costs of £93m/km (at today’s prices). Still, bear in mind that that would be for the tunnel alone. Factor in associated infrastructure such as marshalling yards, stations and new rail connections and you would be looking at another £15bn, pushing the overall price tag up to £30bn.

Route 2 is from Holyhead to Dublin.

 

[Wolfie]

The Fehmarn Belt is managing it with a tunnel length of 18km, a handful of very large gravity base structure like systems could be employed as ventilation if required for longer tunnels

Ultimately the simple answer is you build a viaduct instead.

It doesn't follow that technology that works in a relatively short tunnel would work in one approximately six times as long.

Your last para/sentence is indeed, if you wish to facilitate road transport, the sensible answer. Call it a viaduct, bridge or whatever but do it open air!

Norway can do it! https://www.vegvesen.no/en/roads/Roads+and+bridges/Road+projects/e39coastalhighwayroute

Are any of those proposed tunnels even half as long as UK-Ireland would be? As a general rule of thumb pushing technology is never cheap. It often doesn't work also.

 

[HSTEd]

It doesn't follow that technology that works in a relatively short tunnel would work in one approximately six times as long.

It does when you use ventilation platforms so that it is effectively a series of 18km tunnels in sequence!

 

[zwk500]

Your last para/sentence is indeed, if you wish to facilitate road transport, the sensible answer. Call it a viaduct, bridge or whatever but do it open air!

And close it every time there might be a storm as there's a crossing time of 1 hour and you don't want vehicles to be caught when the wind arrives. So that'd be almost continuous for 2-3 months every winter.

 

[HSTEd]

And close it every time there might be a storm as there's a crossing time of 1 hour and you don't want vehicles to be caught when the wind arrives. So that'd be almost continuous for 2-3 months every winter.

Or you could just engineer the viaduct to allow it to stay open in a storm?

 

[zwk500]

Or you could just engineer the viaduct to allow it to stay open in a storm?

You could, for a price. Probably one ending with 'billions', given the severity and frequency of storms at certain times of the year in that part of the world.

 

[HSTEd]

You could, for a price. Probably one ending with 'billions', given the severity and frequency of storms at certain times of the year in that part of the world.

Billions are just par for the course with a scheme like this.

Given the cost of the overheads, endured forever, of a Chunnel type solution, probably involving larger tunnel bores, extra tracks, extra safety measures, all the operating costs etc etc etc, I am not convinced it will come out more favourable in the long term.

(If you have a road-rail crossing you only need two tracks of railway, a Chunnel type solution certainly requires four, unless you want passenger trains to crawl through the tunnel, wrecking the economics and doing interesting things to the evacuation requirements)

 

[mmh]

Those pondering HGVs on a 70 mile bridge to Dublin would do well to consider just how often the quarter mile bridge between mainland Wales and Anglesey is closed to HGVs in high winds. A lot.

 

[HSTEd]

Those pondering HGVs on a 70 mile bridge to Dublin would do well to consider just how often the quarter mile bridge between mainland Wales and Anglesey is closed to HGVs in high winds. A lot.

Yes, and that bridge is not engineered specifically to remain open to HGVs in those conditions?

I hope you aren't implying that the Menai suspension bridge, or the Britannia bridge, is the best we can do today?

 

[paul1609]

You could, for a price. Probably one ending with 'billions', given the severity and frequency of storms at certain times of the year in that part of the world.

The M4 Prince of Wales, Severn Crossing has wind barriers designed in. It only needs to close when wind speeds are above 70 knots which is very rarely in practise. The whole rail network would be closed because the overhead lines had fallen down by then.

 

[zwk500]

The M4 Prince of Wales, Severn Crossing has wind barriers designed in. It only needs to close when wind speeds are above 70 knots which is very rarely in practise. The whole rail network would be closed because the overhead lines had fallen down by then.

The M4 Severn Crossing is utterly impossible to replicate over 50+ miles of open Irish Sea. The bridge deck is stiffened by being comparatively short spans regularly anchored to piers sunk into the bedrock. All the engineering solutions to an Irish Sea bridge suggest at best tethered semi-submersible piers and long spans to reduce the number of piers required. I would also be very surprised if the wind speeds in the middle of the Irish Sea were as calm as often as those in the Bristol Channel. However, I've never spent much time around either so can't comment on an overall pattern in comparisons.

I would think the best solution for a crossing of this length would be a twin-track bore for passenger rail traffic & fast freight (GB/GC, 200km/h), and 2x single bores for a car shuttle and slower freight (Eurotunnel sized, 100km/h).

 

[HSTEd]

The M4 Severn Crossing is utterly impossible to replicate over 50+ miles of open Irish Sea. The bridge deck is stiffened by being comparatively short spans regularly anchored to piers sunk into the bedrock. All the engineering solutions to an Irish Sea bridge suggest at best tethered semi-submersible piers and long spans to reduce the number of piers required.

Tether semi submersible piers are the oft proposed solution for the North Channel crossing! That has to deal with 300m deep water and all sorts of madness like that, and even then the Norwegians debate whether a semi submersible solution is better thaan a gravity base solution in that sort of depth.

A crossing in the vicinity of Holyhead is considerably shallower, indeed a large part is well below 50m depth, depending on what route you take

It's far too shallow for tension leg piers to be necessary, even at it's ~150m deepest it would be far more reasonable to use a gravity base structure than a TLP solution.

In Norway they built a viaduct in water depths of up to 38m without even resorting to cable stayed spans.

I would also be very surprised if the wind speeds in the middle of the Irish Sea were as calm as often as those in the Bristol Channel. However, I've never spent much time around either so can't comment on an overall pattern in comparisons.

The Lantau link provides at least one lane in each direction that is completely shielded against weather. As wind conditions worsen it is used first for high sided vehicles, and then all vehicles, to keep the crossing partially operational.

I would think the best solution for a crossing of this length would be a twin-track bore for passenger rail traffic & fast freight (GB/GC, 200km/h), and 2x single bores for a car shuttle and slower freight (Eurotunnel sized, 100km/h).

Once you go for a multiple pair tunnel solution, you should design the fast tunnels for much higher speed than only 200km/h and give up on a notion of "fast freight", probably 360km/h design speed.
Freight won't care about being 20 minutes slower in crossing, it can use the shuttle tunnels.

 

[zwk500]

Tether semi submersible piers are the oft proposed solution for the North Channel crossing! That has to deal with 300m deep water and all sorts of madness like that, and even then the Norwegians debate whether a semi submersible solution is better thaan a gravity base solution in that sort of depth.

A crossing in the vicinity of Holyhead is considerably shallower, indeed a large part is well below 50m depth, depending on what route you take

It's far too shallow for tension leg piers to be necessary, even at it's ~150m deepest it would be far more reasonable to use a gravity base structure than a TLP solution.

In Norway they built a viaduct in water depths of up to 38m without even resorting to cable stayed spans.

Not being an engineer can't comment on the feasibility of specific designs, but I'd be very surprised if the span lengths of the link you've provided and the M4 allowed the use of an economic number of piles. I suspect it will be longer spans, which increases the risk of movement of the deck itself.

The Lantau link provides at least one lane in each direction that is completely shielded against weather. As wind conditions worsen it is used first for high sided vehicles, and then all vehicles, to keep the crossing partially operational.

All well and good until the road itself shifts underneath a car. A crossing time of 40-60 minutes means risk mitigation is a very different ball game to most bridges.

Once you go for a multiple pair tunnel solution, you should design the fast tunnels for much higher speed than only 200km/h and give up on a notion of "fast freight", probably 360km/h design speed.
Freight won't care about being 20 minutes slower in crossing, it can use the shuttle tunnels.

Fair point on giving up on fast freight. The design speed of the tunnel will be limited by safety considerations and the like, as well as the need to filter onto the respective networks at either end. 200km/h is 125mph, so still HSR (Or maybe you'd have to do it to 220km/h to tick the box), and importantly is a 15 minute crossing. Even if safety considerations only allow 1 train in the tunnel in each direction, that's 4tph dedicated passenger paths if needed. I also don't see Irish lines being built beyond 250km/h, and the UK option is many times more likely to be an upgrade of the North Wales Coast Line between Crewe and Holyhead than a brand-new dedicated HS link, so I'm presuming 125mph for that.

I may just not be being ambitious enough, of course.

 

[RobShipway]

I cannot see a tunnel between Holyhead and Ireland ever happening to be honest. Look at how much it cost to build the Channel Tunnel and you can times that by about 6, as you are going at least three times the distance than you are going through the channel tunnel.

But I am not an engineer, so why physically it maybe possible to create the tunnel, logically the costs would be too great and never paid back within 100 years.

 

[paul1609]

I cannot see a tunnel between Holyhead and Ireland ever happening to be honest. Look at how much it cost to build the Channel Tunnel and you can times that by about 6, as you are going at least three times the distance than you are going through the channel tunnel.

But I am not an engineer, so why physically it maybe possible to create the tunnel, logically the costs would be too great and never paid back within 100 years.

I agree, new M75 motorway from the Lockerbie area on the M74 to Stranraer area new bridge / tunnel to the M1 south of Lisburn. Forget rail its a waste of time. Need to find reasons to do the job not excuses why its not possible.

 

[HSTEd]

Not being an engineer can't comment on the feasibility of specific designs, but I'd be very surprised if the span lengths of the link you've provided and the M4 allowed the use of an economic number of piles. I suspect it will be longer spans, which increases the risk of movement of the deck itself.

Well I wasn't specifically pointing to that bridge in particular, just pointing out that minimising bridge pile count is not considered to be an overwhelming design criterion in water as deep as nearly 40m.
Given that a large part of the bridge would be in water much shallower than 100m, and gravity base piles are available to depths of several hundred metres, that other criteria will be more important than strictly reducing the number of bridge spans.

It's also worth noting that spans of several hundred metres have been built with tied arches these days, if for whatever reason Cable Stay is considered to aerodynamically unstable, Including this 552m monster.

Myself I would think of something like ~100m extradosed spans with the double deck structure, but that might end up consuming a lot of concrete in piers!

All well and good until the road itself shifts underneath a car. A crossing time of 40-60 minutes means risk mitigation is a very different ball game to most bridges.

The Lantau link is designed to remain open into conditions that would be comparatively rare in the mid Irish Sea, it remains fully aerodynamically stable to very high wind speeds.
As for risk mitigation, I'm very much in the school of "apply additional concrete and steel" to this sort of problem. It is likely possible to engineer a bridge that can remain (at least partially) open throughout a wide variety of wind conditions such that closures (or even threatened closures) are a rare event.

This is also one of the reasons I like the Formby-Ardglass connection.
The long section is in much shallower water (mostly around 30m or less), and then the Isle of Man provides a safe place to abort crossings whereas the deep part of the crossings is concentrated into the shorter section.
So whilst its an enormously long viaduct, it is really two viaducts, one in shallow water that can be very heavily built as a result, and one comparatively shorter one in deeper water.

Even if safety considerations only allow 1 train in the tunnel in each direction, that's 4tph dedicated passenger paths if needed. I also don't see Irish lines being built beyond 250km/h, and the UK option is many times more likely to be an upgrade of the North Wales Coast Line between Crewe and Holyhead than a brand-new dedicated HS link, so I'm presuming 125mph for that.

I may just not be being ambitious enough, of course.

The government would end up looking rather foolish if they engineered the tunnel for 200km/h and then had 320km/h capable trains (because I'm assuming it will be routed via HS2!) crawl through an almost perfectly straight set of tunnels wouldn't they!

Also a 90km Holyhead tunnel would take about ~25 minutes at 200km/h wouldn't it?

 

[Gloster]

Nobody seems to have really dealt with the problem of free passage. Unless the bridge is very high at some point, there will need to be a section of tunnel to allow ships to travel up and down the Irish Sea. The Irish would probably want it to be on their side to avoid everything having to round the Isle of Man.

 

[HSTEd]

Nobody seems to have really dealt with the problem of free passage. Unless the bridge is very high at some point, there will need to be a section of tunnel to allow ships to travel up and down the Irish Sea.

It is likely to be far easier just to have a section of bridge deck with a very high span to allow ships to pass under it than mess around with a tunnel section.

Even the Suez canal has an air draught limitation after all

 

[DerekC]

I cannot see a tunnel between Holyhead and Ireland ever happening to be honest. Look at how much it cost to build the Channel Tunnel and you can times that by about 6, as you are going at least three times the distance than you are going through the channel tunnel.

But I am not an engineer, so why physically it maybe possible to create the tunnel, logically the costs would be too great and never paid back within 100 years.

The politics don't suit a Holyhead - Dublin tunnel although the engineers say it's feasible - see:

https://www.newcivilengineer.com/la...OWAzlCy7coOUurc8d5U28yRyMerphTeb1g-t9DvIDtCig

Wales to Ireland tunnel ‘more attractive’ than Scotland to Northern Ireland link​

26 May, 2021 By Catherine Kennedy


A Wales to Ireland tunnel could prove to be a "more attractive" prospect than the previously suggested Scotland to Northern Ireland link, according to tunnelling expert Bill Grose.
Last week transport secretary Grant Shapps suggested an 80km tunnel to connect Ireland and Wales in an interview with the Financial Times, with reports suggesting the route could run from Holyhead to Dublin.
Tunnelling consultant Bill Grose - a former British Tunnelling Society chair - told NCE that the existing infrastructure in Holyhead and Dublin could make the route a better option than the previously mooted link from Belfast to Stranraer.
"I can see it being more attractive to investors because you’re connecting more existing infrastructure on the Welsh side with more on the Irish side," he said. "Dublin is bigger city than Belfast. There is more infrastructure in Holyhead than Stranraer. It’s less of a business risk."
Given the existing road and rail infrastructure in place in Holyhead and Dublin, Grose said he suspects "the additional landside infrastructure costs would be less".
He added that Liverpool and Manchester are closer to Holyhead than to Scotland so if trade and passenger routes between Britain and Ireland were mapped out, a Wales to Ireland connection "would make more sense from a transport point of view".

Water depth is another key element, with the Irish Sea between Dublin and Holyhead relatively shallow - 120m at its deepest.
Grose explained: "The water is not particularly deep so it would be possible to build an island or put some sort of platform or cofferdam halfway across, either temporary or permanent, to provide some sort of ventilation or access. So I think the water depth helps. It makes it quite attractive in tunnelling terms."
According to Grose, the tunnelling costs would be likely to be in the region of £5bn to £7.5bn with a project cost of £15bn a reasonable first estimate.
It is unclear whether the proposal favours a road or rail tunnel but Grose backed rail as a more realistic option, since technology for long distance rail tunnel travel is more developed than for road tunnels. The tunnel would be almost twice as long as the 50km Channel Tunnel.

A tunnel to the Republic of Ireland wouldn't suit Boris's "strengthening the Union" agenda. The cost-benefit argument applies to any fixed link, but a link to Northern Ireland might have votes attached so is worth spending money on - at least up to the next election.

It is likely to be far easier just to have a section of bridge deck with a very high span to allow ships to pass under it than mess around with a tunnel section.

Even the Suez canal has an air draught limitation after all

That's not what was done for the Øresund crossing - that has a tunnel section complete with artificial island for the transition. My guess is that the need for design against wind plus ice and ship collision risks make a very high span very expensive.

 

[Gloster]

That's not what was done for the Øresund crossing - that has a tunnel section complete with artificial island for the transition. My guess is that the need for design against wind plus ice and ship collision risks make a very high span very expensive.

The bridge across the Great Belt has two low bridges to the west of the island of Sprogø, but a rail tunnel and a road bridge to the east. The eastern bridge is humped and goes up to around 70 metres above water level to provided clearance.

 

[HSTEd]

On the wind speed impacts on a bridge over the Irish Sea, I just had a look at the Lantau Link, including the Tsing Ma bridge, in Hong Kong/

The enclosed road lanes on the bridge remain in operation until the 10 minute mean wind speed reaches 190 km/h, don't have information on the rail link.

50 year return speed in the Irish sea is apparently, hourly mean of 65 knots, with 93 knot gusts, or about 170km/h. [page 6/30]


What we learn from this is that weather in South East Asia is no joke!