Higher speeds and higher costs
The ‘safe maximum speed’ on the soft soil that occurs along much of HS2 route may be as low as 157 mph [253 km/h] according to a report in the Sunday Telegraph.
[HS2 at risk of derailing at top speeds, report finds, Andrew Gilligan,
Sunday Telegraph, 12 Mar 2016]
[…] In [research completed in 2015], Prof Peter Woodward, one of the world’s leading experts in the geo-engineering of railways, found that the speeds proposed by HS2 – faster than any other high-speed line in the world – would create “critical track velocity effects” and “significant issues” with track instability.
[…] HS2 plans to start operations with trains running at 225mph in routine service, then increase speeds – to 250mph – within a few years. Most high-speed lines, including Britain’s Eurostar, run no faster than 186mph in routine service and the world’s current fastest rail-based trains, France’s TGV Est, travel no faster than 200mph.
Research by David Connolly, a colleague of Prof Woodward’s at Edinburgh’s Heriot-Watt University, has found that the safe maximum speed on the soft soil that occurs along much of HS2 may be as low as 157mph.
To avoid the danger, HS2 may have to be slowed to that speed on several stretches, cutting or even eliminating its advantage over conventional rail. Alternatively, there may need to be massive works to stiffen the ground the line runs over, potentially adding billions of pounds to its cost.
Another expert in the field, Prof Victor Krylov of Loughborough University, who produced an influential early academic paper on the subject, said the danger was of a “ground-vibration boom, similar to a sonic boom”, which causes a sudden and “very large” increase in generated ground vibrations.
“What matters is when you cross the [speed] barrier,” he said. “If you do that, ground vibrations can increase twenty, thirty times.”
Prof Krylov said the effect, known as a “Rayleigh wave,” was greatest in soft ground and had been observed in trains travelling as slowly as 110mph in Sweden, across alluvial soil.