HS2 - Government proposals, alternative routes and general discussion

[whole diary]

[ChrisB]

From MSN news
https://www.msn.com/en-gb/news/uknews/work-halted-on-hs2-after-mystery-pool-of-bubbling-foam-appears/ar-AA17GtRN?ocid=winp1taskbar&cvid=c6aed2b8383d45d4a87a561f11de24e4

Work on HS2^▸ (The next High Speed line(s)) was halted on Saturday after a mysterious five-metre square pool of bubbling foam emerged above the ground where tunnelling was being carried out...continues........

I wondered where MSN got this from. It sounds a lot more Guardian than Microsoft, with its default view that technological advances will kill us all, especially anything to do with nuclear power or HS2.

The Guardian logo is at the top of said article....

[paul7575]

HS2^▸ (The next High Speed line(s)) have announced work on the mainline station at Old Oak Common will start in March:

Work on the new HS2 station at Old Oak Common is progressing well and the construction of the conventional station is expected to start on Friday 10 March 2023.
The conventional station includes a new station building and eight above ground platforms that will connect the HS2 Station to the Great Western Main Line and the Elizabeth Line services.
From Friday 10 March 2023, enabling works will start in the location identified on the map on page 2, and will include drainage and groundworks. Then the conventional station structure and walls to support the platforms will be built using concrete.
The eight platforms will be constructed in a phased approach, with platforms 3 to 8 initially built using precast concrete pieces bought into site and lifted into place. Then the main elements of the station roof will be built. These works are expected to be complete at the end of 2025. Network Rail will then divert the existing live railway through the newly constructed platforms over a Christmas possession period, which is expected to take place in 2026. After these works, Platforms 1 and 2 and the final section of the roof structure will be constructed with all these works expected to complete in 2028.

https://www.hs2.org.uk/work-items/notice-of-start-of-the-conventional-station-works/

[ChrisB]

Diary note - NO TRAINS in Paddington area Xmas 2026

[TonyK]

Diary note - NO TRAINS in Paddington area Xmas 2026

Drat!

[stuving]

HS2^▸ (The next High Speed line(s)) have announced work on the mainline station at Old Oak Common will start in March:

This video does appear to show the box being built underground for HS2's station, and the space cleared on the surface for the GWML^▸ (Great Western Main Line) station, and how they relate to each other. Note that the London end of the surface station (its trackwork at least) will overlap the HS2 station box, so that isn't yet available.

[stuving]

So, it was a leak - slurry is used by some TBMs, and it's under pressure to stop the ground collapsing before the linings are in place. I think this is the first drive on which HS2^▸ (The next High Speed line(s)) have used the method - it depends on the nature of the ground. It escaped up some pre-existing channel, such as a borehole (a terrafistula?); ground surveys can't be expected to spot that. Once the TBM has got past it (maybe they drop the pressure a bit for a while) and whatever sort of grout they use around the linings has set - end of problem.

That was based on a hint by HS2 about ground conditions needing a modified tunneling process. But this wasn't a multi-mode (or variable-density) TBM after all, just a plain old EPB one. They routinely inject drilling fluid at the face to keep the consistency of the spoil right for the machinery.

I now have some more explicit sources for this stuff. This from Herrenknecht has details of all HS2's TBMs. And New Civil Engineer explains just after the event what was going on. This also covers the question of whether this borehole was drilled for HS2's ground surveys.

The TBM was paused for approximately two hours between 2pm and 4pm on Saturday to dry the leak. HS2 added that “the borehole is now sealed behind one of HS2’s TBM tunnel rings”.

SCS JV has said it “will continue to monitor the area over the next few days and install additional ground anchors to ensure there is no subsidence”.

Tunnelling specialist Bill Grose believes HS2 did the right thing by stopping the TBM while investigating and then stabilising the situation before carrying on the tunnelling.

He continued: "The reports so far don't say whether it is an HS2 borehole or someone else's. Assuming it's the former, I imagine that there will be some questions asked within HS2.

"Boreholes are usually positioned some distance horizontally from the tunnel alignment and are grouted on completion to prevent this type of occurrence and of course would be recorded on a GIS or BIM^▸ (Building Information Modeling) model for the tunnellers to be aware of.

"The TBM will be injecting drilling fluid, ie the foam, at the tunnel face to keep the face stable and to help remove spoil.  The drilling fluid will be under pressure and will therefore exploit any flow route, such as a fissure or other void at a lower pressure.  The borehole, if not fully sealed would provide a route to ground level for the pressurised drilling fluid."

[ChrisB]

This also covers the question of whether this borehole was drilled for HS2^▸ (The next High Speed line(s))'s ground surveys.

Does it?

He continued: "The reports so far don't say whether it is an HS2 borehole or someone else's. Assuming it's the former, I imagine that there will be some questions asked within HS2.

"Boreholes are usually positioned some distance horizontally from the tunnel alignment and are grouted on completion to prevent this type of occurrence and of course would be recorded on a GIS or BIM^▸ (Building Information Modeling) model for the tunnellers to be aware of.

[stuving]

Does it?

Yes - in the journalistic sense that it reports on it. It does not answer the question, but it does raise it and adds some informed comment.

[infoman]

Listening to five live at 05:30am on Friday 3rd March

Boss of HS2^▸ (The next High Speed line(s)) is about to be interviewed

[Electric train]

Listening to five live at 05:30am on Friday 3rd March

Boss of HS2^▸ (The next High Speed line(s)) is about to be interviewed

I listened to it, he has a very realistic approach to keeping cost under control, he said inflation has had and still is having a large impact on the construction costs.

[TaplowGreen]

Listening to five live at 05:30am on Friday 3rd March

Boss of HS2^▸ (The next High Speed line(s)) is about to be interviewed

I listened to it, he has a very realistic approach to keeping cost under control, he said inflation has had and still is having a large impact on the construction costs.

Was this the discussion?

https://www.bbc.co.uk/news/business-64792328?at_format=link&at_link_origin=BBCPolitics&at_bbc_team=editorial&at_link_type=web_link&at_medium=social&at_ptr_name=twitter&at_link_id=F91188CC-B997-11ED-A637-7D0F3AE5AB7B&at_campaign_type=owned&at_campaign=Social_Flow

[ChrisB]

Yep, that article was based on the interview. On BBC^» (British Broadcasting Corporation - home page) Sounds if needed. Was on 0530-0600

[TonyK]

I heard him also interviewed on Radio 4. As well as inflation, delay is blamed for cost increases.

[TaplowGreen]

I heard him also interviewed on Radio 4. As well as inflation, delay is blamed for cost increases.

Given the way budgets were moving way out of control and the project was way behind schedule long before inflation started to rise to its current levels, I think it's fair to say that blaming these factors for where HS2^▸ (The next High Speed line(s)) is now suggests the brassiest of necks, although it's probably true that the inflation in the construction sector is contributing to costs spiralling ever higher.

It's looking ever more quixotic on every level.

[TonyK]

It's going to come as a real shock when trains start running, especially for anyone still campaigning against it.