From the Archives: Rayleigh Waves and HS2

As background to Mid-Cheshire against HS2’s paper which they presentated to HS2 Ltd, here is some more information about Rayleigh Waves, which they mentioned in the paper. Originally published here (with more information from Heriot-Watt university here).

Several recent news items have discussed the risks to HS2 and the surrounding areas posed by Rayleigh Waves.

These include the Telegraph – High speed rail link ‘at risk of derailment’ because of 225mph trains, the Herald Scotland – High-speed train safety questioned, the Express and Star – Derailment fears over high speed rail scheme and the Oxford Mail Expert warns of HS2 danger.

Rayleigh Waves were first brought up a couple of days after HS2 was originally announced, in 2010, when Peter Woodward, of Herriott-Watt University in Edinburgh, spoke to The Engineer.

According to Woodward, it is most critical to look at the increasing forces and vibrations induced in the track as a train’s speed picks up. ‘A point can be reached whereby a ground wave starts to develop ahead of the train,’ he said. ‘The analogy is that of an aircraft going through the sound barrier.’

These Rayleigh Waves were first predicted in 1885, and have been studied in connection with seismic activity.

In 2000, academics in Nottingham published an article called Rail movement and ground waves caused by high-speed trains approaching track-soil critical velocities in the Journal of Rail and Rapid Transit. The abstract for the paper says

“The obtained theoretical results are illustrated by numerical calculations for TGV and Eurostar high-speed trains travelling along typical tracks built on soft soil.”

As well as the academic articles, David Rayney, submitted evidence to the Transport Select Committee inquiry into High Speed Rail last year – The Application and Effect of the Rayleigh Wave Speed Principle on High Speed Rail travel.

This was followed up by FOI requests, which showed even as late as December 2011 HS2 Ltd were saying

“HS2 Ltd has not at this stage carried out any detailed assessment of possible Rayleigh Wave effects, or any other static or dynamic loading conditions on its potential high speed route sections.

Yesterday, we posted a list of consultant costs which Justine Greening gave as a written answer to Steve Baker MP: these did not include the £500,000 research grant awarded to Prof Woodward and colleagues for research into HS2 and Rayleigh Waves. FOI requests about this research have been refused.

The main HS2 consultation document says on p19

“The focus has been on developing proposals for a safe and reliable railway, using proven European standards, technology and practice.

It’s clear that this statement was misleading, because just as sonic booms are only an issue for the fastest aircraft, rayleigh waves are only an issue when train speeds get above a certain speed (which is different depending on the ground conditions).

HS2 Ltd needs to have HS2 running at speeds faster then most current high speed trains to get the economic case to stack up.

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