GEOTECHNICAL AND TRACK ENGINEERING
Cotswold Line fl ooding
Haltwistle
St Bees 2012
Identifying F
ollowing a season of rain and storms, it is ever more important that Network Rail acts to adequately prepare and maintain its assets across the railway, and tries to reduce the impact of severe weather on passengers.
And this could be a phenomenon which is becoming increasingly common – with more than 30 extreme asset failures this year, compared to fewer than fi ve the year before.
RTM spoke to Network Rail’s route asset manager and geotechnical engineer Julian Harms about the types of damage such weather could infl ict, and how the company was working to improve its risk predictions and respond effectively to high-level hazards.
Extreme hazards
In response to the wet and windy months the railway has undergone this summer, Harms said: “There is no question that extreme types of weather event appear to be becoming more prevalent.
“This year has been exceptional. In the past fi ve months we’ve had extreme rainfall events that have caused asset failures in each of those months, in some cases multiple asset failures.”
48 | rail technology magazine Oct/Nov 12
earthworks risk
Julian Harms, route asset manager and geotechnical engineer for Network Rail on earthworks, discusses recent severe weather and the industry’s response.
Monitoring is in place around the network to ensure the team has advance notice of movement occurring, and can respond with an intervention plan as soon as possible.
Despite having one of the “best and most comprehensive tools anywhere”, Harms admitted that it was still not picking up on high-risk locations “as well as it could do”.
This summer, a number of the locations that failed in the North West were either ‘serviceable’ or ‘marginal’, according to the hazard rating. Network Rail is therefore looking into different ways to analyse its data and identify factors unique to failure sites, to ensure a reliable indicator for risk. He commented: “That’s not something the system the currently does very well, and we are applying ourselves to do.”
Studies are ongoing in this area, as well as work on interventions to reduce the risk to the travelling public and members of rail staff. These could include using proving engines to check key lines following extreme weather, and setting thresholds for what exactly constitutes ‘extreme’ weather before triggering an intervention.
As a last resort, imposing speed limits can
reduce the speed at which a train would encounter a landslip, were one to occur, Harms said.
However, this response is unpopular due to its effect on performance and customer satisfaction.
He added that Network Rail could begin to make more use of its helicopters to scout for incidents and locations where water is accumulating to highlight areas of risk.
Categorising concern
Harms said: “The damage that has been caused falls into a number of categories. The issues which cause us the most concern in the short term are the failures which affect cutting slopes.”
The two main failure types that cause such concern are earthfl ow failures – where soils in the cutting slope turn to a liquid state and fl ow onto the slope, bringing debris and boulders with them onto the track – and wash-out, where surface water erodes down into the cutting slope and brings loose material onto the track.
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