How was Westminster station reconstructed?

[trebor79]

I know essentially a bridge for the sub surface lines was built underground and then the box for the Jubilee line and escalators excavated below.
But how was that bridge built without shutting the sub surface lines for a long time?

 

[Dstock7080]

The sub-surface lines were closed almost every weekend for several months.
The track was temporarily suspended on blocks in small sections, with new concrete foundations being built below.
There were times when a 10mph speed restriction was imposed and a look down would reveal a deep excavation under the tracks.
I believe the track and platform were lowered eventually lowered by 50cm.

 

[rebmcr]

I believe the track and platform were lowered eventually lowered by 500cm.

That doesn't seem possible, is this a typo of 50cm?

 

[Dstock7080]

That doesn't seem possible, is this a typo of 50cm?

Indeed 50cm

 

[trebor79]

The sub-surface lines were closed almost every weekend for several months.
The track was temporarily suspended on blocks in small sections, with new concrete foundations being built below.
There were times when a 10mph speed restriction was imposed and a look down would reveal a deep excavation under the tracks.
I believe the track and platform were lowered eventually lowered by 50cm.

Ah, that makes sense. Essentially dig a big hole under part of the track, cast some foundations (which I guess eventually became entombed in the "bridge" structure), pack the track up on the new foundations. Next weekend do the next section. Then gradually lower everything (I knew that the lowering had happened, something to do with Portcullis House being built above). Then cast the bridge in sections and it's then relatively simple to excavate beneath all that.
It would be interesting to find some civil engineering magazine articles from the time, must have been quite a project!

 

[Snow1964]

I visited there a few times, the track was literally in short sections, there was bolted fishplate joint about every 2m so could be quickly removed each weekend to dig out and build new trackbed. There was lots of temporary timber work under the sleepers for a while.

I believe the track lowering was so the ticket hall could be built above the tracks with a flat floor (and still have headroom under the new Portcullis building.

The old Westminster station had footbridges over the tracks, and the far one (Embankment end) was served by a small station entrance in Portland Stone that was built as a trial (along with back entrance to Bond Street) ahead of building the Northern lines southern extension to Morden.