High Speeds in Tunnels

[edcayton]

With everyone seeming to want longer tunnels on HS2, I'm wondering how much discomfort people suffer when going through tunnels at very high speeds. I think that the fastest I have been would have been on the Eurostar when it ran "The White Rose" service to York all those years ago, but I suspect that was limited to 125 mph.

 

I don't know how fast the trains on HS1 go through the tunnels, and have not travelled on high speed trains in Europe, so any thoughts please?

 

Thanks

 

Ed

[eastwestdivide]

I've had worse discomfort (pressure changes) from the single-track tunnels on the ECML between London and Stevenage than in the HS1 tunnels in Eurostars or Javelins. The Eurostar doesn't slow down for the North Downs tunnel, at least as far as I could tell.

There was a dumbed-down science programme on Channel 5 or similar which described the "piston effect" in tunnels on high speed lines, where they described specially-shaped tunnel mouths to mitigate the pressure effects.

Disclaimer: I'm not an engineer.

[phil-b259]

The basic answer is it depends on three factors.

 

(1) How well the passenger space is sealed, in particular the door arrangements. For example 319s have sliding doors which rattle and flex as the train passes other trains or indeed passes through tunnels. 377s meanwhile have plug doors which provide a much better seal so making pressure changes less noticeable (though the hopper windows and lack of air con in the 319s don't help either). When plans were first revealed there was much criticism of Hitachi's decision to go back to sliding doors for the Javelin units in view of this but in practice the sliding doors fitted to the Javelins have lived up to expectations.

 

(2) The diameter of the bore, with a larger bore not only being good at reducing the pressure effects, it is actually more efficient as pushing a large lump of air in front and dragging air in behind is pretty wasteful of energy - some of which is turned into heat.

 

(3) The number, type and design of any piston relief measures (as in the Channel tunnel to mitigate the flow) plus the design of the portal structure

[Ron Heggs]

The basic answer is it depends on three factors.

 

(1) How well the passenger space is sealed, in particular the door arrangements. For example 319s have sliding doors which rattle and flex as the train passes other trains or indeed passes through tunnels. 377s meanwhile have plug doors which provide a much better seal so making pressure changes less noticeable (though the hopper windows and lack of air con in the 319s don't help either). When plans were first revealed there was much criticism of Hitachi's decision to go back to sliding doors for the Javelin units in view of this but in practice the sliding doors fitted to the Javelins have lived up to expectations.

 

(2) The diameter of the bore, with a larger bore not only being good at reducing the pressure effects, it is actually more efficient as pushing a large lump of air in front and dragging air in behind is pretty wasteful of energy - some of which is turned into heat.

 

(3) The number, type and design of any piston relief measures (as in the Channel tunnel to mitigate the flow) plus the design of the portal structure

 

Cannot comment on the train designs

 

Worked on the design of the services within the North Downs Tunnel - the tunnel bore and shape were designed for two trains passing each other at 300kph both in terms of the forces and frequency of the pressure waves generated, including ventilation without the need for additional or supplementary ventilation ducts. I assume that tunnels on HS2 would be designed on similar principles

 

Ron

[tetsudofan]

Most of the research into high speeds in tunnels has been done in Japan where high-speed trains have been running since 1964 - I think it's fair to say that the Japanese are world-leaders into high-speed train design.

 

The latest shinkansen to enter service in Japan travel at speeds of upto 320kph and there are plans to increase this to 360kph in due course. Most of the new shinkansen lines being built have a high percentage of tunnels than HS2 will ever have. The trains are designed for high speed and it's interesting see how the "long-snout" designs have developed as speeds have increased. The Japanese have also spent a lot of time perfecting the pantograph design on the latest shinhansens.

 

Also being built is the super-highspeed maglev line a lot of which will be in tunnels with trains reaching in excess of 450kph - but it will be a few years before this line is operational.

 

Recently I took a trip on Eurostar and it's interesting that I felt my ears "popping" on Eurostar before reaching the Chunnel something that has never happened to me on a SouthEastern Cl.395 travelling on the same track......but then the Cl.395s were built in Japan based upon one of their mini-shinkansen varients.

 

Keith

[phil-b259]

 

Recently I took a trip on Eurostar and it's interesting that I felt my ears "popping" on Eurostar before reaching the Chunnel something that has never happened to me on a SouthEastern Cl.395 travelling on the same track......but then the Cl.395s were built in Japan based upon one of their mini-shinkansen varients.

 

Keith

 

Its worth remembering the class 395s are a good deal younger than Eurostars - so not only will the technology be better but simply the newness of the components will make a difference.

[Edwin_m]

The 395 shuts off its aircon intakes when approaching a tunnel - don't know about Eurostar. 

[Dazzler Fan]

+

For tunnels, both lines from Swindon to Bristol and Bristol Parkway have twin lines in

the tunnels giving full pressure effect from opposing HST trains. I don't know if there

is a speed limit on the particular stretches.

The 5:59pm ex Paddington regularly did the 113 miles to Bristol Parkway in under the hour.

 

+

[roythebus]

GWR tunnels are wider than everywhere else, thanks to I.K.Brunel.

[The Stationmaster]

GWR tunnels are wider than everywhere else, thanks to I.K.Brunel.

But not on the Badminton Cut-Off - that was built and opened after the Company completely converted to narrow gauge

[Fat Controller]

But not on the Badminton Cut-Off - that was built and opened after the Company completely converted to narrow gauge

Nor one of the two bores on the Patchway tunnel, for the same reason.

I'd be interested to know if people get 'popping ears' on Eurostar when using the Channel Tunnel; the internal fire-doors are closed remotely when approaching it, which should reduce the decompression.

[jonny777]

Of the tunnels on the ex-GWR main lines, it is the single bores at Patchway which have the biggest effect on my ears.

[The Lurker]

I don't recall popping ears on the chunnel but I do on the HS1 line - my youngest found it funny - which is good as he has ASD and is hyper sensitive to some things

[Fat Controller]

I don't recall popping ears on the chunnel but I do on the HS1 line - my youngest found it funny - which is good as he has ASD and is hyper sensitive to some things

That would fit with my comments about the closure of the internal fire-doors; they only shut these for the Channel Tunnel.

[edcayton]

They also don't go that fast through the Chunnel do they?  Thanks for all the replies so far guys.

 

Ed

[Fat Controller]

They also don't go that fast through the Chunnel do they?  Thanks for all the replies so far guys.

 

Ed

160 kph

[Coppercap]

But not on the Badminton Cut-Off - that was built and opened after the Company completely converted to narrow gauge

 

 

Nor one of the two bores on the Patchway tunnel, for the same reason.

 

 

While it is true that the Badminton Cut-Off was completed after the GWR's abolition of the Broad Gauge in 1892, the second Patchway tunnel was opened in 1886, concurrent with the Severn Tunnel (as Narrow Gauge, as the GWR put it), and therefore it opened before the end of the Broad Gauge..........

[peanuts]

read somewhere that one of the single bore tunnels at standage was used for experiments on the nature of this during the late sixties for the channel tunnel that was abandoned know some of the vents have been capped off so could be true 

 

 trying to remember which book it was think it may have been the saddleworth railways one 

[62613]

read somewhere that one of the single bore tunnels at standage was used for experiments on the nature of this during the late sixties for the channel tunnel that was abandoned know some of the vents have been capped off so could be true 

 

 trying to remember which book it was think it may have been the saddleworth railways one 

 

read somewhere that one of the single bore tunnels at standage was used for experiments on the nature of this during the late sixties for the channel tunnel that was abandoned know some of the vents have been capped off so could be true 

 

 trying to remember which book it was think it may have been the saddleworth railways one 

 

read somewhere that one of the single bore tunnels at standage was used for experiments on the nature of this during the late sixties for the channel tunnel that was abandoned know some of the vents have been capped off so could be true 

 

 trying to remember which book it was think it may have been the saddleworth railways one 

 'A Regional History of the Railways of Great Britain Vol. 10: The North-West' by Geoffrey O. Holt certainly mentions it (p.151 in mine!)

[buffalo]

GWR tunnels are wider than everywhere else, thanks to I.K.Brunel.

But not on the Badminton Cut-Off - that was built and opened after the Company completely converted to narrow gauge

While it is true that the Badminton Cut-Off was completed after the GWR's abolition of the Broad Gauge in 1892, the second Patchway tunnel was opened in 1886, concurrent with the Severn Tunnel (as Narrow Gauge, as the GWR put it), and therefore it opened before the end of the Broad Gauge..........

Surely, the relevant date here is not the end of the Broad Gauge in May 1892 but the end of new construction of Broad Gauge track? Give or take a few chains, this would be around 1865, though there were a few more miles of new build by Broad Gauge companies later acquired by the GWR.

 

Nick

[peanuts]

 'A Regional History of the Railways of Great Britain Vol. 10: The North-West' by Geoffrey O. Holt certainly mentions it (p.151 in mine!)

probarbly your copy i read bro

[kenw]

. I think that the fastest I have been would have been on the Eurostar when it ran "The White Rose" service to York all those years ago, but I suspect that was limited to 125 mph.

 

Yes, the Eurostar was subject to normal line speeds when running on the ECML. With regard to tunnels. the highest speed anywhere through a tunnel on the line's 115mph, in several cases falling on entering or rising on exiting.

As previously suggested, the tunnel design / bore's the major factor, e.g. Potters Bar / Hadley Wood tunnels, in the Up direction through the original narrow bore GN tunnels the Fast Line's 100mph, in the Down direction through the wider bore 1950s BR tunnels the Fast lines 115mph.

[david.hill64]

It's not so much the length of the tunnel that gives rise to the pressure pulses as the entrance/exit, which as other posters have noted, can have measures such as flared portals and pressure relief ducts to relieve the situation.

 

I worked on the Taiwan high speed rail project, which is unusual in using UIC infrastructure standards - including tunnel bore sizes - with Japanese trains. The Japanese tried to get the project to adopt the smaller Shinkansen tunnel bore, which would have saved a significant amount in tunnelling costs, but the project stuck with the larger bore. This was beneficial for the trains: the trains are essentially pressure tight which means that the body shells inflate and deflate as the exterior pressure falls and rises. The Japanese spent a lot of time examining this phenomenon and I suspect that the relatively small windows are influenced by structural strength considerations as much as anything else (the Japanese vehicles are relatively light weight and about half as strong as European high speed vehicles).

 

Some years ago I had to spend a day riding the WCML between Birmingham and Euston in 86's and an 87. I remember the amusement of the driver and inspector at my reaction when we entered Linslade tunnel single bore: it literally took my breath away.

[The Stationmaster]

Surely, the relevant date here is not the end of the Broad Gauge in May 1892 but the end of new construction of Broad Gauge track? Give or take a few chains, this would be around 1865, though there were a few more miles of new build by Broad Gauge companies later acquired by the GWR.

 

Nick

Very much so Nick.  the original Patchway Tunnel of the Bristol & South Wales Union Railway  was traversed by a broad gauge line and that was converted to narrow gauge (in GWR parlance) in 1873; the original route to South Wales, via Gloucester, had been converted to narrow gauge in 1872.  Hence both the Severn Tunnel and the second tunnel at Patchway were constructed for narrow (standard) gauge lines as the South Wales route had by the time of their construction been operating on narrow (standard) gauge for more than 10 years.

[The Great Bear]

Hs2 tunnels have porous portals, extension to portal with either holes in roof or walls to alleviate pressure transition effects IIRC