Elizabeth Line (CrossRail) opened 24th May 2022

I was thinking about the tunnels on the Elizabeth line...

As far as I can work out most of the tunnels are twin bore / single track (Paddington - Stratford / Custom House, the Thames Tunnel plus Woolwich station and Heathrow Airport).

However the refurbished Connaught tunnel plus approaches is twin track / single bore.

Am I correct?

Yes, although the centre section of the original Connaught tunnel was twin single track tunnels, this was reconstructed as part of Crossrail's construction
A 2010 London Reconnections article and 2011 IanVisits article both have photos of the old tunnel
Timelapse video of the 2013 reconstruction
2017 cab ride video from shortly after completion

As were Paddington and Canary Wharf stations - these are I believe (at the most basic level) single large boxes with two bored tunnel portals at each end.

Yes, Woolwich and Paddington were cut and cover, in the case of Paddington the glass canopy over the ticket hall and escalators has become an artwork with the design of every known cloud formation etched (or painted, or whatever) on the glass.

Canary Wharf was not cut and cover - at least not in the normal way. Instead the East India north dock was drained and the station plus retail complex and roof garden were built inside the dock. It might me that they had to dig a bigger / deeper hole, on that I am unsure - but I suspect that they did have to do this.

Once all building works had been sufficiently completed the dock was allowed to fill with water again and then what amounts to a moat was created around the new construction

information source:

www.crossrail.co.uk/route/stations/canary-wharf/

re: the Connaught tunnel, I read somewhere that they were going to upgrade it via one method and then before they started work further investigations made them realise that it would not have worked - instead what they were going to do would have risked the roof caving in!

In the end the solution they adopted included converting it from twin single bore to one twin track bore.

The new tunnel wasn't bored.

There was some concern that there might be unexploded bombs in the dock. To avoid risks the dock was drained and the tops of the old tunnels removed.

The other parts were excavated to allow a new box tunnel using precast sections to be constructed and the dock refilled. The schedule was very tight as there was a military trade fair at the ExCel and several warships were to be displayed in the dock.

Hello, first post in the forum even though I’ve been silently reading for years.
Does anyone know what the four digit codes on the side destination panels of Elizabeth Line trains mean? Something in this format: 9T72.
Apologies if this has been discussed before.

It's the train headcode or train reporting number, which is a national rail thing.
The first digit is the class of train, 9 being a high priority passenger service. Most other passenger trains use class 1 (express) or class 2 (ordinary).
The letter indicates the destination, the Elizabeth line trains seem use the ones below, but they are only unique on a given route.
C Gidea Park (from Liverpool Street high level)
N Maidenhead
R Reading
T Heathrow (any terminal)
W Shenfield
U Abbey Wood
Y Paddington
the last two digits are a serial number.

In theory at least, in any four hour window any train passing a given station should have a unique headcode. For example there are five 9Y01 services today the 0516 Thameslink service from Blackfriars to Sevenoaks and the Elizabeth line services from Shenfield to Paddington at 0918, 1333, 1754 and 2246. 9T72 could be either the 1247 Abbey Wood to Heathrow Terminal 4 or 1706 Abbey Wood to Hearhrow Terminal 5. For more information see Wikipedia's Train reporting number article.

It's far less common to see it on a passenger display though.

Thank you everybody for your answers regarding the headcode.
Talking about unusual situations with the Elizabeth Line and National Rail, I noticed that Elizabeth Line services appear in a very inconsistent way in the National Rail app. Some stations, especially the ones in the core that do not interconnect with an existing mainline station, cannot be searched directly in the app. But it seems to me that all services are trackable both through National Rail and TfL’s API.
But for example right now if I search for departures from Tottenham Court Road (TCR) I get a list, if I search for Bond Street (BSZ) I get a random “you seem to be offline” error.
Also Abbey Wood departures seem to leave from ABWDXRS two
minutes before going to Abbey Wood.

This is very inconsistent compared to Overground trains that are all tracked fine.

As an IT person, I wonder if it was their goal to make trains properly trackable only on TfL whilst somehow also using the NR infrastructure as well.

Who actually calls it a train reporting number though? Certainly on the train planning side, we call them headcodes and so does our software.

Do you have a link to those?

From Sunday 21st May, already viewable on Realtime Trains and other equivalents

I am not surprised at all that there are no direct trains between Reading/Maidenhead and Shenfield, but I am mildly surprised there will no regular direct trains between Canary Wharf and T5.

I was honestly expecting the new service to be T4 to Shenfield.

Also worth noting I guess, the 2tph uplift from Abbey Wood will terminate at London Paddington.

Its currently 2tph Abbey Wood - T4 and 2tph Abbey Wood - T5

From May it will be 4tph Abbey Wood - T4 and 2tph Shenfield - T5

I guess that by sending all the Abbey Wood trains to T4 you can keep an even 15 min headway, while if they were split between T4 and T5 the headways would be uneven.