HS2 construction updates

[Tobbes]

Twin bore with cross passages is simply cheaper. It produces less spoil and needs less concrete than a double bore tunnel. The logistics of getting rid of the spoil are usually the key constraint on tunnelling speed. The quantities are enormous.

TBMs are indeed started a couple of months apart, and it does help with settlement and the first machine gives advance warning of ground conditions - although on this latter point pilot drilling is often carried out from the TBM in addition to all the ground investigations done from ground level beforehand. But the main reason they are set off a couple of months apart is that that’s how they come off the production line at Herrenknecht (other TBM manufacturers are available), and a specialist team comes over to assemble and commission them. The same team does both, but they can only do one at a time. This also helps with the back up logistics for spoil and segments; it means that for the first couple of months the logistics are on ‘half power’ which makes it easier to shakedown any issues.

Thanks @Bald Rick , very interesting as ever.

 

[jyte]

Do we know when they intend to start tunnelling? I'm presuming sometime in the next 12 months?

I remember Crossrail having a 'track our TBMs' map, I think it would be cute if HS2 did the same thing.

 

[LNW-GW Joint]

Eurotunnel had 11 TBMs for 12 drives (2 running tunnels and the intermediate service tunnel, bored both ways from 2 access shafts).
They all set off in staggered fashion from the coastal shafts, with the landward TBMs reaching the open air for dismantling in situ.
Except the TBM for the short French landward running tunnel which was reversed to bore the second running tunnel, and was then dismantled at the coastal shaft.
The 6 under-sea TBMs were driven off-line when they met in mid-Channel (actually nearer France), and the guts of them are still there!

TML (the contractor) published the position of each TBM weekly as they progressed, after they were criticised (validly) for secrecy over project progress.
You had to ring up on a Tuesday morning for a voice recording of the updated figures, which were vital to continued confidence in the project, as TML came close to bankruptcy more than once over delays and cost increases.
I used to write the numbers down in a list each week, but close to the end I dropped the list somewhere on Paddington station so lost the records!
(This was before spreadsheets and instant-access web-sites).
Somewhere, those numbers were eventually published in a report - fascinating evidence of the highs and lows of an incredibly complex and politically sensitive project.
I'm looking forward to something similar (but maybe a bit more high-tech) for measuring HS2 tunnelling progress.
We just have to hope for no "running sand" problems (as at Farnworth) or tunnel collapses (DB's new routes in Germany).

 

[gingertom]

Twin bore with cross passages is simply cheaper. It produces less spoil and needs less concrete than a double bore tunnel. The logistics of getting rid of the spoil are usually the key constraint on tunnelling speed. The quantities are enormous.

TBMs are indeed started a couple of months apart, and it does help with settlement and the first machine gives advance warning of ground conditions - although on this latter point pilot drilling is often carried out from the TBM in addition to all the ground investigations done from ground level beforehand. But the main reason they are set off a couple of months apart is that that’s how they come off the production line at Herrenknecht (other TBM manufacturers are available), and a specialist team comes over to assemble and commission them. The same team does both, but they can only do one at a time. This also helps with the back up logistics for spoil and segments; it means that for the first couple of months the logistics are on ‘half power’ which makes it easier to shakedown any issues.

I do hope they are able to move the spoil by rail, there's an awful lot of lorry loads if they can't.

 

[Bald Rick]

Eurotunnel had 11 TBMs for 12 drives (2 running tunnels and the intermediate service tunnel, bored both ways from 2 access shafts).
They all set off in staggered fashion from the coastal shafts, with the landward TBMs reaching the open air for dismantling in situ.
Except the TBM for the short French landward running tunnel which was reversed to bore the second running tunnel, and was then dismantled at the coastal shaft.
The 6 under-sea TBMs were driven off-line when they met in mid-Channel (actually nearer France), and the guts of them are still there!

TML (the contractor) published the position of each TBM weekly as they progressed, after they were criticised (validly) for secrecy over project progress.
You had to ring up on a Tuesday morning for a voice recording of the updated figures, which were vital to continued confidence in the project, as TML came close to bankruptcy more than once over delays and cost increases.
I used to write the numbers down in a list each week, but close to the end I dropped the list somewhere on Paddington station so lost the records!
(This was before spreadsheets and instant-access web-sites).
Somewhere, those numbers were eventually published in a report - fascinating evidence of the highs and lows of an incredibly complex and politically sensitive project.
I'm looking forward to something similar (but maybe a bit more high-tech) for measuring HS2 tunnelling progress.
We just have to hope for no "running sand" problems (as at Farnworth) or tunnel collapses (DB's new routes in Germany).

I, too, kept track of tunnelling progress for the Channel Tunnel, and mapped it all out week by week on a chart made from 4 pieces of graph paper sellotaped together. They are in my loft somewhere.

As an aside, some of the Crossrail TBMs have been buried where they finished. Near Farringdon for a couple, I think.

I do hope they are able to move the spoil by rail, there's an awful lot of lorry loads if they can't.

Yep it’s going by train.

 

[chappers]

The spoil arising from Chiltern Tunnels is predominately going to sustainable placement sites. There is no rail connection in the vicinity to allow it to be removed by rail

 

[Ianno87]

The spoil arising from Chiltern Tunnels is predominately going to sustainable placement sites. There is no rail connection in the vicinity to allow it to be removed by rail

But has had a brand new junction built directly onto the M25 so at least the lorries are going straight on/off the motorway from the portal construction site.

 

[Bald Rick]

Yep it’s going by train

Quoteing myself. What I meant was ‘mostly’ going by train.

 

[CW2]

@Bald Rick
Quoting yourself is the first sign of madness!

 

[Bald Rick]

@Bald Rick
Quoting yourself is the first sign of madness!

Well I don’t think there was any doubt about that

 

[themiller]

Eurotunnel had 11 TBMs for 12 drives (2 running tunnels and the intermediate service tunnel, bored both ways from 2 access shafts).
They all set off in staggered fashion from the coastal shafts, with the landward TBMs reaching the open air for dismantling in situ.
Except the TBM for the short French landward running tunnel which was reversed to bore the second running tunnel, and was then dismantled at the coastal shaft.
The 6 under-sea TBMs were driven off-line when they met in mid-Channel (actually nearer France), and the guts of them are still there!

The first TBMs to finish 'mid-channel' were driven off-line and had their heads disconnected before dismantling the remainder. The heads were buried and form earth points. The other TBMs had their heads cut-up in situ on completion of their drives and their 'tails' were dismantled and recovered.

 

[Lockwood]

Dumb question...

Why do TBMs bury themselves and die? Are they unable to back out (I get not being able to go forwards if they meet their counterpart going towards them)?

It seems quite a big item to commit technosuicide. I would have thought there'd be cost savings to rescuing them. Clearly not, otherwise that would happen.

 

[gsnedders]

Dumb question...

Why do TBMs bury themselves and die? Are they unable to back out (I get not being able to go forwards if they meet their counterpart going towards them)?

It seems quite a big item to commit technosuicide. I would have thought there'd be cost savings to rescuing them. Clearly not, otherwise that would happen.

I'm sure others can explain better than me, but fundementally the front of the TBM is larger than the bored tunnel: it's the size of the exterior of the concrete ring lining the tunnel (after all, it has to cut a hole large enough for the lining to go in!), so you can't reverse it. So to get the front of the TBM out, you have to have access to the front (either because the drive ended at the surface or you construct an access shaft to extract it, potentially cut up), and ensuring access frequently becomes more expensive than just burying it. The tail is more often than not dragged back out regardless of what happens to the front of the TBM: it fits in the tunnel anyway!

 

[Bald Rick]

Dumb question...

Why do TBMs bury themselves and die? Are they unable to back out (I get not being able to go forwards if they meet their counterpart going towards them)?

It seems quite a big item to commit technosuicide. I would have thought there'd be cost savings to rescuing them. Clearly not, otherwise that would happen.

I'm sure others can explain better than me, but fundementally the front of the TBM is larger than the bored tunnel: it's the size of the exterior of the concrete ring lining the tunnel (after all, it has to cut a hole large enough for the lining to go in!), so you can't reverse it. So to get the front of the TBM out, you have to have access to the front (either because the drive ended at the surface or you construct an access shaft to extract it, potentially cut up), and ensuring access frequently becomes more expensive than just burying it. The tail is more often than not dragged back out regardless of what happens to the front of the TBM: it fits in the tunnel anyway!

Exactly. All the tail of the TBM is reversed out for want of a better phrase; and what can be recovered from the head end usually is. What’s left behind is the outer casing, cutting head, and the big chunky elements that are too difficult to shift for their scrap value.

In addition, the front end of TBMs are often knackered (or close to it) when they are finished, particularly on long drives. They can’t easily be used again in these circumstances. On shorter drives most elements can be used again, but they need extensive refurbishment. Herrenknecht (other TBM manufacturers are available) often have first refusal on what is recovered and reuse elements for ‘pre-loved’ TBMs.

 

[Lockwood]

Ah, that makes sense. I was imagining the whole unit digging itself a grave

 

[edwin_m]

Presumably the tunnel behind the TBM can't be fully fitted out if the tail of the TBM has to be backed out first.

 

[Ianno87]

Presumably the tunnel behind the TBM can't be fully fitted out if the tail of the TBM has to be backed out first.

No, it'll generally be backed out before the rails, ventilation and other railway systems are installed.

 

[Bald Rick]

Presumably the tunnel behind the TBM can't be fully fitted out if the tail of the TBM has to be backed out first.

Yep it comes out almost as soon as the boring has stopped.

 

[civ-eng-jim]

Does anyone know if this continued on through the lockdown?

Yes - Very much so.

 

[furnessvale]

Yep it comes out almost as soon as the boring has stopped.

Presumably an adaptation of a standard boring machine. Normally the diameter of the cutting head is sufficient to accomodate the lining which, once fitted, would stop a straightforward reverse.

 

[NotATrainspott]

The AlpTransit projects (Gotthard and Ceneri Base Tunnels) seemed to have quite good status updates on the website. There was a diagram showing all the elements to be tunnelled and fitted out and what stage each one was at on a weekly basis. It was interesting to see how the different tunnelled elements happened in sequence.

 

[si404]

Why do TBMs bury themselves and die?

Typically, they don't.

The one (out of 11) 'buried at sea' (to use Eurotunnel's term) on the Chunnel was because of specific very circumstances

• The tunnel was bored from both ends due to length - it couldn't just emerge out the other side like HS2's tunnels will do.
• The tunnel was undersea - and so, unlike Crossrail TBMs ending their drive mid-tunnel at Farringdon, Stepney Green and the Limmo Peninsula, you couldn't have a big hole down to the tunnel's level that would allow you to remove the head vertically. Projects might choose not to dig down without a load of sea getting in the way, but obviously there was zero chance of doing this.

I think the one that ended up digging its own grave had a more dignified end than the one that sat next to the M20 with a 'For Sale' on it for years. That that one eventually was sold on eBay shows how long it took to go (and even then, for scrap).

 

[edwin_m]

Yep it comes out almost as soon as the boring has stopped.

That does mean that none of the tunnel drive can be fitted out until all of it has been bored. But perhaps there is too much stuff in there for spoil removal and transport of segments to make any sensible fitting-out possible until it is all cleared away.

 

[civ-eng-jim]

There'll be a fair few cross passages to dig which are all done by hand (Well, smaller tools than a TBM!) - At least one every 500m.

There are a couple of low points in the tunnels so there'll probably be a sump and some hefty pumps too.

 

[Bald Rick]

That does mean that none of the tunnel drive can be fitted out until all of it has been bored. But perhaps there is too much stuff in there for spoil removal and transport of segments to make any sensible fitting-out possible until it is all cleared away.

Exactly, the logistics for the tunnel boring usually prevent any fitting out until the tunnel is dug. D the fitting out is often done inside out, ie start in the middle and work back.

 

[jyte]

Recent drone footage from Birmingham Interchange:

 

[jyte]

Oh and another from a different Youtuber of land clearance around Kenilworth

 

[mmh]

I, too, kept track of tunnelling progress for the Channel Tunnel, and mapped it all out week by week on a chart made from 4 pieces of graph paper sellotaped together. They are in my loft somewhere.

As an aside, some of the Crossrail TBMs have been buried where they finished. Near Farringdon for a couple, I think.



Yep it’s going by train.

Where to?

 

[LNW-GW Joint]

That does mean that none of the tunnel drive can be fitted out until all of it has been bored. But perhaps there is too much stuff in there for spoil removal and transport of segments to make any sensible fitting-out possible until it is all cleared away.

Well there's the mine-standard narrow gauge railway that has supported the TBM operation for a start!

I'm reminded that another large bored tunnel is under construction at the moment - the Woodsmith Mine tunnel in North Yorkshire.
This will be the longest tunnel in the UK when finished (37km), running from the Sirius Minerals mine near Whitby to Redcar.
It's 6m in diameter so well up to railway dimensions (HS2 tunnels will be 9.1m, Crossrail is 6.2m), and it will contain a conveyor for the mined potash mineral.
Currently being bored by Strabag of Austria with 3 TBMs, completion 2021.

Woodsmith Mine Tunnel - Wikipedia

en.wikipedia.org

 

[civ-eng-jim]

Where to?

Possibly here:

Plan to fill quarry with HS2 debris raises concerns over noise pollution and harm to wildlife

A project to level off and landscape Parkfield Road Quarry by filling it with soil and clay from the high-speed rail project has been green-lit by Warwickshire County Council

rugbyobserver.co.uk