Tunnel Re-boring

[Legolash2o]

I've been catching up on the Transpennine thread and there was mention of re-boring tunnels.

My questions are how does it work (boring machine?), how long does it take, how costly is it and why isn't it considered more often for locations such as Standedge, Stalybridge and Scout Tunnels?

I suspect it's too disruptive and significantly increases the cost, which in turn impacts the cost-benefit analysis.

There a new piece on TP electrification in Railway Gazette, suggesting there is increasing optimism about wiring the full route:
Trans-Pennine electrification hopes rise | Rail Business UK | Railway Gazette International

 

[hwl]

Farnworth didn't exactly go to plan...

Farnworth Tunnel - Once in a lifetime - Rail Engineer

Listen to this article Unique is an overused word and it’s often applied erroneously. Whilst all rail projects are different – due to the location and scheme design – there is always some commonality between, for example, every bridge replacement or track renewal. But the same cannot be said of...

www.railengineer.co.uk

Farnworth Tunnel Electrification.

I've been told that people who live nearby to the Tunnel/Station have received letters from Bolton Council OBO Network Rail, that work will start in April for 6 months. No trains will stop during the period and Bustitution will not reach the station but call in Farnworth centre, due to the local...

www.railforums.co.uk

Plenty more out detail out there if you search for "Farnworth Tunnel".

Huge risk cost element uplift as well.

 

[LNW-GW Joint]

Many tunnels already have adequate clearance for wiring (eg Severn Tunnel, or those on the southern WCML), but Farnworth didn't, and it was in very difficult ground.
The Pennine tunnels will be of very hard rock which is more difficult for TBMs, and might be drilled/blasted like most Alpine tunnels.
The Channel Tunnel, and the Chiltern tunnels for HS2, are largely through soft-ish chalk, and the many tunnels under London are through clay, both ideal for TBMs.
Water ingress is another factor which determines if TBMs are used, and which type.
The TBMs at the French end of the Channel Tunnel were of a different design to those at the English end because of the higher water content on the French side.

 

[pdeaves]

Another thing to remember in possibly enlarging tunnels is that there may be 'other stuff' outside of the tunnel lining. Obviously that's more likely in congested urban areas (e.g. London) than the middle of the countryside, but the possibility is still there. You don't want to dig through and disturb someone's house foundations, for example. So it can be better to leave things be than take the risks. Of course, if the need was that great, the powers that be may be more likely to take the risk (which equates to higher project costs).

 

[zwk500]

I've been catching up on the Transpennine thread and there was mention of re-boring tunnels.

My questions are how does it work (boring machine?), how long does it take, how costly is it

Effectively, you fill in the old tunnel and bore a new one (usually with a TBM). How long it takes depends on ground conditions, rock type and how different the lining & filling is from the outer rock. Again the cost will vary depending on how complicated the job is. You need to strip the old tunnel to avoid damage to the tunneling equipment, then fill in the void to avoid collapse, before starting the actual re-bore, at which point you are on new-build timings and costs.

and why isn't it considered more often for locations such as Standedge, Stalybridge and Scout Tunnels?

I suspect it's too disruptive and significantly increases the cost, which in turn impacts the cost-benefit analysis.

You've answered you're own question. You can't run trains while you're filling the tunnel in or reboring it, so you'd be looking at closing Standedge Tunnel for at least a year. Farnworth was only possible because there were 2 independent bores, and the timetable could be juggled around to permit single-line working for the duration. You can't close Standedge or Stalybridge Tunnels for more than a year.

 

[Legolash2o]

Thanks for the replies.

I just read up a bit on Farnworth, seems like the main issue was sand which hopefully wouldn't apply to the three tunnels I mentioned but the harder rock impacting time-scales and the houses above Stalybridge would be the issue as pdeaves mentioned.

 

[Bald Rick]

You can't run trains while you're filling the tunnel in or reboring it, so you'd be looking at closing Standedge Tunnel for at least a year.

And the rest. Farnworth (270 metres) took 7 months. Standedge Tunnel is 4,883 metres long. As they say in America, do the math!

 

[Legolash2o]

You've answered you're own question. You can't run trains while you're filling the tunnel in or reboring it, so you'd be looking at closing Standedge Tunnel for at least a year. Farnworth was only possible because there were 2 independent bores, and the timetable could be juggled around to permit single-line working for the duration. You can't close Standedge or Stalybridge Tunnels for more than a year.

Yeah, I can't imagine the route being closed for year. Even six months would be a pain!

And the rest. Farnworth (270 metres) took 7 months. Standedge Tunnel is 4,883 metres long. As they say in America, do the math!

You could temporary re-open the closed tunnels next to Standedge but that would definitely add cost to what would be an already expensive project, just to design those lines and do that work (repairing, making sure it's safe, up to standard, etc). That's assuming you can even get the funding.

 

[zwk500]

I just read up a bit on Farnworth, seems like the main issue was sand which hopefully wouldn't apply to the three tunnels I mentioned but the harder rock impacting time-scales and the houses above Stalybridge would be the issue as pdeaves mentioned.

Harder rock will be more stable (less risk) but harder to bore through (takes longer). Also in the Pennines you will have lots of potential water ingress issues. If there's a spring nearby it'll cause many more problems than sand.

Yeah, I can't imagine the route being closed for year. Even six months would be a pain!

Even a weekend is a big enough pain!

You could temporary re-open the closed tunnels next to Standedge but that would definitely add cost to what would be an already expensive project, just to design those lines and do that work (repairing, making sure it's safe, up to standard, etc). That's assuming you can even get the funding.

At Standedge, the most likely answer to any gauge or capacity enhancement will be a brand new bore. If the current gauge and capacity are fine, there are easier and cheaper solutions to electrical clearance problems in the current bore.

 

[QueensCurve]

I've been catching up on the Transpennine thread and there was mention of re-boring tunnels.

My questions are how does it work (boring machine?), how long does it take, how costly is it and why isn't it considered more often for locations such as Standedge, Stalybridge and Scout Tunnels?

I suspect it's too disruptive and significantly increases the cost, which in turn impacts the cost-benefit analysis.

There is a redundant tunnel alongside the present Standedge tunnel. There may be options involving that. Noting of course that there may be difficulties an complications involved.

One option that was suggested (these fora passim?) was to reroute the line into the redundant tunnel while doing the works.

Another solution might be to make the redundant tunnel electrification ready then permanently divert the line into there.

A possibility might be to put one track in the existing tunnel and one into the other.

Notfor a moment suggesting these are easy options. Perhaps others can suggest what difficulties they would present and how these might be overcome.

 

[Legolash2o]

You could re-instate the adjacent tunnels whilst the work is complete and then keep it as slow lines in the long-term. Heading into speculative territory here so I'll stop there and I'm sure it's been discussed in the speculative forum already .

Harder rock will be more stable (less risk) but harder to bore through (takes longer). Also in the Pennines you will have lots of potential water ingress issues. If there's a spring nearby it'll cause many more problems than sand.

Even a weekend is a big enough pain!

Completely forgot about springs if I'm honest and the potential nightmare.

Thanks everyone for answering my questions, appreciated!

 

[Bald Rick]

The answer for Standedge is to electrify the current tunnel. It’s really not that much of a problem.

 

[zwk500]

There is a redundant tunnel alongside the present Standedge tunnel. There may be options involving that. Noting of course that there may be difficulties an complications involved.

There are in fact 2 redundant rail tunnels (each single track, I think), as well as the in-use canal tunnel next to the current Standedge tunnel.

One option that was suggested (these fora passim?) was to reroute the line into the redundant tunnel while doing the works. Another solution might be to make the redundant tunnel electrification ready then permanently divert the line into there.

You could re-instate the adjacent tunnels whilst the work is complete and then keep it as slow lines in the long-term

Even if you got permission for lower standards as a temporary line, bringing the tunnel up to code is still likely to cost nearly as much as bringing it up to full permanent standards. Especially as you'd have to do 2 tunnels. Even for the temporary option you'd need to reline the tunnel, make sure it's gauge clear for current traffic and fit signalling, fire protection and some level of escape route. For a permanent route you'd be reboring both single track tunnels out completely AND reconstructing all the cross-passages for fire safety.

As @Bald Rick has said, the current tunnel isn't a problem to electrify.

 

[norbitonflyer]

If there is the space, boring a new tunnel is likely to be less disruptive and cheaper than prepping the old one and then digging it out. This is what was done at Woodhead in the 1950s. Also the stock answer to why the Waterloo & City Line and/or Northern City can't be upgraded - it would be quicker, cheaper, and less disruptive (and result in two lines instead of just one) to build a new tunnel between the South Western and Great Northern main lines - which is what Crossrail 2 is all about.

The conversion of the City & South London Line in the 1920s is probably the biggest project of that kind - hugely disruptive, but easier than most tunnels because the iron tunnel lining segments could be re-used, and because a new tunnel would have required rebuilding of the existing stations (14 of them - although one - City Road - was closed).

 

[Bald Rick]

The conversion of the City & South London Line in the 1920s is probably the biggest project of that kind - hugely disruptive

Rather dangerous too, as it turned out.

 

[swt_passenger]

Thanks for the replies.

I just read up a bit on Farnworth, seems like the main issue was sand which hopefully wouldn't apply to the three tunnels I mentioned but the harder rock impacting time-scales and the houses above Stalybridge would be the issue as pdeaves mentioned.

Farnworth new also wasn’t really a bored tunnel, it was “open face” excavated using conventional diggers, so although within a protective steel shield it wasn’t a TBM. (Often wrongly reported as such.) I don’t think it was long enough for the full TBM set up, which is presumably much safer in variable ground conditions.

 

[quantinghome]

Rather dangerous too, as it turned out.

The write up by Follenfant on the C&SLR conversion is very matter of fact but all the more hair-raising for what it describes - the tunnel collapse created a huge crater on Borough High Street, then the gas main exploded.

But then they were using a ring shaped shield which allowed trains to run through it during the day, then did the excavation work at night:



A similar system was used in the 1990s to replace corroded lining on the Northern line near Old Street.

 

[zwk500]

Farnworth new also wasn’t really a bored tunnel, it was “open face” excavated using a conventional digger, so although within a protective steel shield it wasn’t a TBM. (Often wrongly reported as such.) I don’t think it was long enough for the full TBM set up, which is presumably much safer in variable ground conditions.

Ah thanks for that little bit of info!

 

[hwl]

And the rest. Farnworth (270 metres) took 7 months. Standedge Tunnel is 4,883 metres long. As they say in America, do the math!

Of which only ~50m in total is a problem for electrification + W12 so reboring the whole lot is overkill so a more localised solution is likely...

 

[Legolash2o]

The write up by Follenfant on the C&SLR conversion is very matter of fact but all the more hair-raising for what it describes - the tunnel collapse created a huge crater on Borough High Street, then the gas main exploded.

But then they were using a ring shaped shield which allowed trains to run through it during the day, then did the excavation work at night:
View attachment 99414


A similar system was used in the 1990s to replace corroded lining on the Northern line near Old Street.

Wow, that's crazy stuff.

Of which only ~50m in total is a problem for electrification + W12 so reboring the whole lot is overkill so a more localised solution is likely...

Is there room in the current tunnels for OHLE and W12? Or at least W10?

 

[zwk500]

Is there room in the current tunnels for OHLE

Yes, with a few specialised solutions in places.

and W12? Or at least W10?

Fairly moot, as nobody wants to run a W10/12 through it.

 

[LNW-GW Joint]

Of which only ~50m in total is a problem for electrification + W12 so reboring the whole lot is overkill so a more localised solution is likely...

Presumably that's at the eastern end where the tunnel begins its sharp southward curve (which also prevents higher speeds on the eastern approaches).
The other issue related to the disused bores is whether one or both are needed as freight loops, in which case they would need wiring anyway.

 

[Legolash2o]

Yes, with a few specialised solutions in places.

Fairly moot, as nobody wants to run a W10/12 through it.

I've been in discussion where a FOC said they would like to, or at least thought about it but can't.

Traffic currently has to go around via Lichfield joining the WCML (eating capacity) or use low deck/box wagons which cuts into the amount of containers you can carry and other costs impacting profit margins. But then again it's not always good to have shorter routes because f I remember correctly, rail is better for longer journeys but then again, if you have to think about capacity and environment then avoiding the main lines and shorter routes would better. Could be debated all day probably

Personally I wouldn't like to have freight on the route and believe Calder valley would probably be better suited for freight. Apart from Miles Platting Jn, I can't remember the gradients on that route. I'm open to being completely wrong!

 

[Revaulx]

The answer for Standedge is to electrify the current tunnel. It’s really not that much of a problem.

Looking at the size of the portals I can’t see there will be any problem at all. Unless it “does a Box” and the bore gets smaller once inside. Given the late construction date (1894?) this seems highly unlikely

Stalybridge and Scout presumably date from the line’s construction in the 1840s and do look tighter, though they are also both much shorter. Scout’s almost adjacent canal tunnel is great fun to walk through, incidentally.

 

[Bald Rick]

Is there room in the current tunnels for OHLE and W12? Or at least W10?

Traffic currently has to go around via Lichfield joining the WCML (eating capacity) or use low deck/box wagons which cuts into the amount of containers you can carry and other costs impacting profit margins.

Well this is the issue. I don’t know the detail so what follows is hypothetical... but there could be a scenario where it needs only a few limited clearance works necessary to get the line electrified, but to get to W10 would mean a long rebuild (for example like was done at Ipswich in 2004, just 15 times longer). Clearly the latter would cost a lot, lot more, and be very disruptive. Would the freight companies like to pay for that extra work to help improve their margins?

I do hear, often, industry people say ‘well if their doing this work, they may as well do the extra’, but the ‘extra’ in this case could be much much more than th minimum:required for electrification.

 

[snowball]

Farnworth new also wasn’t really a bored tunnel, it was “open face” excavated using conventional diggers, so although within a protective steel shield it wasn’t a TBM. (Often wrongly reported as such.) I don’t think it was long enough for the full TBM set up, which is presumably much safer in variable ground conditions.

Indeed, through press releases (as in lies, damned lies and press releases) described Fillie as "Britain's largest TBM" on the flimsy excuse that (being sized for double track) it was larger in diameter than the real TBMs on Crossrail.

 

[coppercapped]

At least a couple of tunnels have been enlarged in Germany for DBAG while trains have continued to run. See this website from GTA Maschinensysteme GmbH : https://www.gta.eu/en/downloads-en/...oducts/56-tunnel-enlargement-machine-tem-8400

 

[zwk500]

At least a couple of tunnels have been enlarged in Germany for DBAG while trains have continued to run. See this website from GTA Maschinensysteme GmbH : https://www.gta.eu/en/downloads-en/...oducts/56-tunnel-enlargement-machine-tem-8400

Interesting concept, will the smaller clearances in our tunnels to start with be too great a problem to overcome? There's also not many tunnels where enlargement is needed that could sustain a single-track service for the duration of the reboring.

 

[XAM2175]

Interesting concept, will the smaller clearances in our tunnels to start with be too great a problem to overcome? There's also not many tunnels where enlargement is needed that could sustain a single-track service for the duration of the reboring.

In both of the examples GTA list the original tunnels were dual-track so the majority of the working space came from singling them for the duration of the works, so in theory I'd suggest that yes, a similar process could be used on dual-track tunnels here if so desired and if the geotechnical situation supported it.

The interesting thing to know from a logistical perspective would be how much slower it is than a full closure.

 

[61653 HTAFC]

Pretty much all the freight that runs through the Pennines runs via Brighouse or Hope Valley anyway. The Manchester waste trains used to run via Huddersfield but rarely if ever does these days. Likewise the Liverpool to Drax biomass mostly goes via Hebden Bridge and Brighouse.