How Come HS1 Is OK in the Heat But Not the Conventional Network?

[Envoy]

I see that HS1 (Channel Tunnel to London) was OK in the heat but the conventional network had major problems. Is the type of long welded rail different? What about the over head wires and was the more modern GWR mainline catenary able to cope better with the excessive heat? What about the old fashioned jointed rail now confined to some minor routes such as the Heart of Wales - does that warp?

 

[janahan]

An engineer would probably answer this better, but I suppose the fact that HS1 has faster, longer trains, the fixings, as well as anchoring of sleepers (as well as using concrete as opposed to ballast) all factor into the resiliance for these lines?

 

[Geeves]

I agree with janahan. You'd assume on HS1 that the fact the lines are designed for such high speeds that construction process allows for less movement and the rails are stressed differently? Could be totally wrong.

 

[JN114]

Simply, it is designed to cope with it.

The higher stresses expected for very high speed running help with the default ranges; but unlike much of the traditional network it was designed to beat its specifications not match them.

 

[LNW-GW Joint]

A spokesperson from ORR said on R4 yesterday that HS2's slab track would prevent heat distortion.
HS1 isn't slab track in the open, but it and its OHLE is built to SNCF LGV standards so presumably is designed to cope.
Network Rail maintain it, too.

Most of NR's own slab track is in tunnel which doesn't suffer from high ambient temperatures.
New electrification since 2010 has used auto-tensioners, which might perform better than the traditional pulleys and weights.
However, new HSLs on the continent use pulleys and weights...

 

[Bald Rick]

Simple answer is that is was designed for it. It is all on high spec sleepers, with high spec rail, with well maintained ballast, and (importantly) not much in the way of curves (obviously).

Having said all that, I understand they were very close to putting on a speed restriction yesterday.

 

[fgwrich]

What also probably helps it is the lesser frequency of services running over it (less services, less heat generated).

As for how traditional jointed rail fared, NR shared 3 photos of yesterdays track buckling, and one of those was traditional jointed Bullhead Rail at West Ealing.

 

[Taunton]

Simply, it is designed to cope with it ... unlike much of the traditional network it was designed to beat its specifications not match them.

And there we have the answer ... not engineered down to the minimalist specification.

 

[Dai Corner]

And there we have the answer ... not engineered down to the minimalist specification.

Or over-engineered, it could be argued?

 

[Spartacus]

And there we have the answer ... not engineered down to the minimalist specification.

No, built from the ground up to modern standards, rather than trying to take a then top class 19th century standard and build it up to 21st century standards. Building new it's much easier to build a resilient railway than trying to take into account embankments with varying consistencies because they were built with pick and shovel, and sharp curves that practically beg to be distorted, etc, all while trying to run some sort of service.

 

[snowball]

Or over-engineered, it could be argued?

The weather is only going to go on getting hotter, so no.

 

[Yorkshire222]

How does the UK network compare with the continent? Most of their tracks won't be built for very high speed, presumably HS1 is similar to TGV lines, but "normal" lines won't be. France and Spain have certainly been experiencing higher temperatures for much longer periods so what do they do differently?

 

[Bald Rick]

And there we have the answer ... not engineered down to the minimalist specification.

Or, actually, originally designed for the 21st century rather than the 19th.

How does the UK network compare with the continent? Most of their tracks won't be built for very high speed, presumably HS1 is similar to TGV lines, but "normal" lines won't be. France and Spain have certainly been experiencing higher temperatures for much longer periods so what do they do differently?

I’ve posted about this on other threads on the subject. They don’t do anything differently (with one exception). They both have had days of significant disruption. A train derailed in Spain on buckled track. Various incidents of the wires being down, etc etc.

the one exception is that they tend not to do any work to the track which risks a reduction to the critical rail temperature in their high summer. We do.

 

[Taunton]

Or, actually, originally designed for the 21st century rather than the 19th.

One would have thought that the rails and ballast might have been renewed from time to time in the interim, to current standards rather than 19th century designs.

In actual fact, the track seems to have held up throughout. I'm told on another thread that lineside fires have been the main issue, but I'm not aware how 21st century design improves over 19th century in this respect.

 

[Teaboy1]

Bullhead rail came/comes in typically 60 foot [59ft-3in] lengths with fish-plate joints. The small gap will typically accept 3-4mm expansion so the whole thing generally will not distort when it gets hot.
Continious welded rail typically comes in 1km lengths with an engineered expansion joint designed to accomodate much greater expansion. Dont know the exact numbers without looking them up but 1 km will expand by some 88 mm for a temperature rise of say 60 degC [ thats from 15 degC to 75 degC].
Slab track is much more heavily engineered with concrete sleepers and is massively ballasted so less likely to move compared to the old stuff.
Plus it dont need anywhere near as much maintence with its 120 joints per km to check over by a track gang. Less prone to broken rail also from my brief experience.

 

[The exile]

Or, actually, originally designed for the 21st century rather than the 19th.



I’ve posted about this on other threads on the subject. They don’t do anything differently (with one exception). They both have had days of significant disruption. A train derailed in Spain on buckled track. Various incidents of the wires being down, etc etc.

the one exception is that they tend not to do any work to the track which risks a reduction to the critical rail temperature in their high summer. We do.

It’s also worth considering that though yesterday’s temperatures would have been exceptional virtually anywhere in Europe, the further south you go, the less exceptional they will be. The “once in a century” event will probably never pass the vfm test - once it becomes once (or more) in a decade it maybe had to be taken into consideration.

 

[Boodiggy]

Bullhead rail came/comes in typically 60 foot [59ft-3in] lengths with fish-plate joints. The small gap will typically accept 3-4mm expansion so the whole thing generally will not distort when it gets hot.
Continious welded rail typically comes in 1km lengths with an engineered expansion joint designed to accomodate much greater expansion. Dont know the exact numbers without looking them up but 1 km will expand by some 88 mm for a temperature rise of say 60 degC [ thats from 15 degC to 75 degC].
Slab track is much more heavily engineered with concrete sleepers and is massively ballasted so less likely to move compared to the old stuff.
Plus it dont need anywhere near as much maintence with its 120 joints per km to check over by a track gang. Less prone to broken rail also from my brief experience.

Not sure where you got your info but Bullhead Rail will have greater movement at expansion joints. For properly regulated joints the rails should be tight at 38 degrees rail temp but have a 10mm gap at zero degrees. Obviously there are lots that can affect the JCT (Joint Close Temperature). CWR does not have expansion joints (assume you mean adjustment switches?) every 1km. The track is continuously welded and and stressed and there will only be an adjustment switch where this changes to jointed track, there is unstrengthened S&C etc.
Most issues with the heat that affect the track will be due to the ballast being disturbed. If the track is stressed or joints properly regulated to correct gaps and fishplates lubricated there will be less risk in the heat.

 

[plugwash]

What about the old fashioned jointed rail now confined to some minor routes such as the Heart of Wales - does that warp?

My understanding is that just as pre-tensioned CWR has a "zero stress temperature", jointed rail will have a "joint close temperature", either way once these temperatures are exceeded the rail will be under compression. Once the rail is under compression you become reliant on the sleepers and ballast to resist buckling.

 

[Boodiggy]

My understanding is that just as pre-tensioned CWR has a "zero stress temperature", jointed rail will have a "joint close temperature", either way once these temperatures are exceeded the rail will be under compression. Once the rail is under compression you become reliant on the sleepers and ballast to resist buckling.

Exactly this.
CWR has a SFT - Stress Free Temperature.

 

[Bald Rick]

One would have thought that the rails and ballast might have been renewed from time to time in the interim, to current standards rather than 19th century designs.

indeed they have, in most cases. In some case it’s not possible though.

The alignment hasn’t been redesigned though, neither have the cutting / embankment face angles, nor width of formation, nor many (most?) of the underline / over line structures, nor the base formation, nor the location of junctions, etc etc. All of which can be affected more by the weather When designed for the 19th century than 21st.

 

[GRALISTAIR]

Or over-engineered, it could be argued?

no

The weather is only going to go on getting hotter, so no.

Yes

 

[yorkie]

It's hardly over-engineering to ensure it copes in unusual conditions.

The fact they didn't have to put a speed restriction in place yesterday is impressive; the fact they were close to doing so demonstrates there was no over-engineering going on.

 

[Class 170101]

I see that HS1 (Channel Tunnel to London) was OK in the heat but the conventional network had major problems. Is the type of long welded rail different? What about the over head wires and was the more modern GWR mainline catenary able to cope better with the excessive heat? What about the old fashioned jointed rail now confined to some minor routes such as the Heart of Wales - does that warp?

The GWML is rather bulky compared to say the NW Triangle kit but how much of the track, ballast etc changed from pre electrification to post electrification?

 

[plugwash]

I would imagine that headspans, as widely used on the ECML increase the sagging problems compared to cantilevers or portals, used on most modern schemes. They also mean that if things do go wrong they tend to go wrong for all lines at once.

 

[Cletus]

Simple answer is that is was designed for it. It is all on high spec sleepers, with high spec rail, with well maintained ballast, and (importantly) not much in the way of curves (obviously).

Having said all that, I understand they were very close to putting on a speed restriction yesterday.

I used HS1 yesterday afternoon, passing Wennington just as the fire was starting, and my speed app was suggesting we were doing 125mph, so a slight reduction in speed.

 

[Hadders]

I used HS1 yesterday afternoon, passing Wennington just as the fire was starting, and my speed app was suggesting we were doing 125mph, so a slight reduction in speed.

That's normal. I think the Javelin service is timed at 125mph but can do 140mph when making up time.

 

[Cletus]

That's normal. I think the Javelin service is timed at 125mph but can do 140mph when making up time.

Oh, I always thought they did 140mph all the time where possible and never really ever made up time.

 

[Bald Rick]

That's normal. I think the Javelin service is timed at 125mph but can do 140mph when making up time.

correct; depending on who is driving of course

 

[Nicholas Lewis]

Simple answer is that is was designed for it. It is all on high spec sleepers, with high spec rail, with well maintained ballast, and (importantly) not much in the way of curves (obviously).

Having said all that, I understand they were very close to putting on a speed restriction yesterday.

Systra were lead designers and given they are largely owned by SNCF i guess they applied French LGV practice to HS1 which presumably is designed for a higher ambient temperature than UK standard.

There certainly is probably a case to have a Southern and Northern temp range now for the infrastructure to work within but as you've said on other thread weather-disruption-sunday-17th-july-and-following-few-days fires were root cause of many of the infrastructure faults.

 

[Bald Rick]

Systra were lead designers and given they are largely owned by SNCF i guess they applied French LGV practice to HS1 which presumably is designed for a higher ambient temperature than UK standard.

HS1 is effectively a French railway. All French specifications. Even the rule book is French (but translated). Best not tell the Government.

HS1 stresses the rails to 28C. That can cope with ambient 41C, hence how close to speeds they were yesterday. The OLE is to a much higher tension, because it has a level contact wire.

Another difference is the absolute intolerance for anything other than knee high vegetation inside the fence or within striking distance of the rail infrastructure.