Is Euston Northern Line (Charing X branch) station safe?

[fandroid]

On Friday I travelled on the Northern Line south from Euston to Battersea Power Station. I noticed this strange pattern in the station tunnel ceiling. As a civil engineer it dawned on me that what I was looking at was exposed steel reinforcement in the concrete lining to the roof. Bits of concrete had apparently already dropped off, presumably due to corrosion in the steel reinforcement bars. If I was responsible for the integrity of that structure, I would be seriously unhappy about it!

 

[bramling]

On Friday I travelled on the Northern Line south from Euston to Battersea Power Station. I noticed this strange pattern in the station tunnel ceiling. As a civil engineer it dawned on me that what I was looking at was exposed steel reinforcement in the concrete lining to the roof. Bits of concrete had apparently already dropped off, presumably due to corrosion in the steel reinforcement bars. If I was responsible for the integrity of that structure, I would be seriously unhappy about it! View attachment 171454

Not entirely sure that’s what you’re looking at there. What can be seen is the actual tunnel segments, which are cast iron.

What has come off is purely the finishing, which is there for aesthetic purposes. Whilst it may have failed, there is work going on here at present to construct a new cable and ventilation tunnel as part of the HS2 works, so it’s possible the finish may have been removed on purpose.

Agree it doesn’t give a good impression though.

 

[edwin_m]

The cast iron segments are exposed over the entire tunnel apart from the stations, so it's evidently not a hazard to expose some of them within the station itself.

 

[fandroid]

OK. I accept that it's cast iron segments that are exposed here, so structurally it's probably OK. But once some of the concrete is exposed, any moisture in the air is going to accelerate surface corrosion of those segments. That corrosion, however modest, will steadily reduce the adhesion of the concrete lining. Then bits will fall off onto the track or onto trains.

Unless the concrete around the iron ribs has been deliberately removed for some reason, it looks as if quite a lot has already fallen off!

 

[Nym]

Concrete Adhesion wouldn't be my main concern if working in this area given the grout is an ACM (Asbestos Containing Material) if this hasn't been touched in some time. And given that (I believe) this is an AP-JNP (Asset Protection - Jubilee Northern Piccadilly, formally TLL Tube Lines Ltd.) managed station, I doubt that campaign replacement work of encapsulated ACM would have been carried out. Indeed this concrete does look >30 years old in this location atop of the tunnel rings.

I also very much doubt it will be standard 'concrete' blends being used to provide the remedials around here, a higher strength adhesive grout would be a lot more likely. I'd also point out that from my experience, Euston CX tunnels are actually quite dry in this area.

 

[Surreytraveller]

On Friday I travelled on the Northern Line south from Euston to Battersea Power Station. I noticed this strange pattern in the station tunnel ceiling. As a civil engineer it dawned on me that what I was looking at was exposed steel reinforcement in the concrete lining to the roof. Bits of concrete had apparently already dropped off, presumably due to corrosion in the steel reinforcement bars. If I was responsible for the integrity of that structure, I would be seriously unhappy about it! View attachment 171454

I'm not a civil engineer, but I know they are the tunnel lining segments

 

[bramling]

OK. I accept that it's cast iron segments that are exposed here, so structurally it's probably OK. But once some of the concrete is exposed, any moisture in the air is going to accelerate surface corrosion of those segments. That corrosion, however modest, will steadily reduce the adhesion of the concrete lining. Then bits will fall off onto the track or onto trains.

Unless the concrete around the iron ribs has been deliberately removed for some reason, it looks as if quite a lot has already fallen off!

There’s unlikely to be much moisture. LU tube tunnels are generally very dry. So much so that rails on little used sidings don’t rust.