Although RAIB’s final report into last year’s tragic derailment at Stonehaven is still awaited, we know now that a significant contributing factor was heavy rainfall washing material onto the track. The accident resulted in the first earthwork-related fatality since the death of a guard at Ais Gill on the Settle-Carlisle line in January 1995.
Rail Engineer recently met up with the first full-time earthworks asset steward, Gerry Manley, to learn about the early proactive management systems and how Network Rail has improved the stewardship of earthworks.
History lesson
When the rail network was built in the 1800s, thousands of embankments and cuttings were constructed and Network Rail now has to manage over 190,000 earthwork assets. The network was built rapidly and, in places, poorly – without the knowledge of soil mechanics and geotechnical engineering that exists today.
If you look at most railways constructed by the Victorians, you will note that the cutting and embankment slopes are far steeper than those of a modern road or railway and do not offer the same resilience to failure. A report by Thomas Telford as long ago as 1829 said that many railway embankments were largely formed by the end-tipping of material down the formation. This was a process Telford specifically disapproved of as it would “delay consolidation and increase the tendency for slipping”.
Nearly 200 years later, geotechnic earthwork engineers are in place on all regions and the asset management process has much improved.
The price of failure
Following rail privatisation in 1994, a small group of asset engineers was formed in each Railtrack region to act as asset owner and steward. Their role was to monitor asset performance and specify interventions on a risk basis, as well as auditing the maintenance contractors. These engineers were organised on a discipline basis for track, signalling, electrification and plant, telecoms, structures and buildings. However, there was no dedicated asset steward for earthworks and with only a small HQ support resource for geotechnics.
It generally fell to the regional track engineers to look after earthworks, but they were not resourced to do so proactively; many did not have the required knowledge or experience. They had enough to do with keeping track geometry compliant so there was no, or very little, proactive management of earthworks.
At Ais Gill, a Carlisle-bound Sprinter was derailed by a landslide and was run into by another Sprinter travelling south. Four years later, a similar incident occurred a few miles south at Crosby Garrett, north of Kirkby Stephen, where 100 tonnes of material caused a Carlisle-bound Sprinter to derail. A southbound coal train weighing 1,392 tonnes then hit the Sprinter; fortunately, nobody was seriously hurt this time.
In January 1999, Rail magazine’s headline read “Is the S&C safe?” and reported on other landslips and incidents that had occurred on the route. It was suggested the S&C should not stand for ‘Settle and Carlisle’, but for ‘Slippage and Collision’.
The Crosby Garret failure was attributed to a crest drain that had become blocked over the years, along with a nearby spring with water collecting in a ground concentration feature outside the railway boundary. Generally, the asset inspection regime did not adequately look at crest drainage, nor beyond the fence. Something had to be done as the earthwork risks and failures were not just on the S&C. So Gerry Manley was appointed as a full-time geotechnic asset steward engineer in Manchester to establish and lead a robust proactive earthwork asset management regime for the region.
Scoping exercise
Gerry was an experienced railway Charted geotechnical engineer with a civil engineering degree and a Masters in geotechnics. He had been involved in earthwork design in BR days in York, working in the Soil Mechanics department. Back then, most of the earthwork activity around the network was reactive – once failures had occurred – or on new formations for limited railway enhancements. Gerry had also taken part in the Ais Gill inquiry, so he knew of some of the issues on the S&C route.
As the first earthwork asset steward, his first insight into the challenge ahead was being asked to draft his own job description, as none existed! Another immediate concern was that the entire earthworks budget for the north-west region was only a few hundred thousand pounds. This was exceedingly small considering the number of earthworks. He was also handed a large volume of paperwork detailing concerns which no-one had been able to focus much attention on.
A consultant’s report was available detailing 36 at-risk earthwork locations on the S&C route, so Gerry visited every one to prioritise and scope the required interventions. This established 14 locations where major work was required, costing millions of pounds. Until the work was carried out, a mitigation measure was implemented consisting of rain gauges to identify excessive local rainfall. When pre-determined thresholds were exceeded, special emergency speed restrictions were put in place. The system was crude by today’s standards, but it was a step in the right direction.
Good drainage
Making a case to investment panels and other asset stewards to release their budget is always a challenge; many hours of stakeholder consultation, negotiation and risk assessment were needed to identify the required budget and gain approval to carry out both minor and major interventions. The objective was to use the available data to identify and fix the root cause of earthwork failures, rather than just treating the symptoms.
Shortcomings in communication are present in nearly all risk management failures and justifying the work undertaken on earthworks required effective dialogue to ensure the leadership team and stakeholders properly understood the risks and their implications.
Following work at the 14 high-risk sites, it only took one minor earthwork failure on another part of the region for the investment panel to question if the money had been spent in the right place. This is a problem asset engineers often face and it requires qualified, professional, responsible leadership to demonstrate the proper management of risk and that a robust ‘stich in time saves nine’ strategy is in place.
It was frequently found that deficiencies in the local drainage system and surface water standing on, or flowing from, adjacent non-railway land increased the risk of failure. Heavy rain was – and is – the most dominant weather event to cause harm to earthworks and, with the extreme weather becoming more frequent, the risks are increasing. Attention was therefore needed to manage water events occurring in locations where they had not been observed before.
The track inspection regime carried out by maintenance contractors was, in many cases, just that – a track inspection with little visual monitoring of the earthwork slopes and cuttings. So, cards were produced to assist patrollers in identifying possible earthwork stability issues, along with A3-size posters for staff cabins. These were very well received during a Railway Inspectorate audit of the region and were recommended as best practice across the network. It is believed that the materials are still in use today, as is the original soil and rock slope hazard index system developed by Gerry.
Good communication with other asset engineers was required so that, for example, signal and telecoms engineers did not remove the toe of cuttings to install cable routes or equipment without proper consideration of the earthwork asset.
Network Rail can manage activities within their boundary, but that is not always the case for activities undertaken by third parties and neighbours. A farmer who previously ploughed his field parallel to the railway may change to ploughing perpendicular to it; this can increase the amount of surface water flowing towards the line.
There was also a situation where a housing developer removed the bottom of a 14m high viaduct approach embankment to extend the size of the gardens on offer. Gerry was on site when a couple arrived to inspect their shiny new house, only for them to find it being demolished so urgent stabilisation works could be undertaken! The developer ultimately had to pay costs to the railway, running into millions of pounds.
New technology
Today, competent and experienced railway geotechnical engineers are in place on every route and region. It is an interesting but challenging role. Earthworks condition will always be a risk, no matter what budget and resources are available, and the assets’ ability to perform reliably will need careful management, particularly at times of prolonged rainfall. With the hotter climate which we are already experiencing, rainfall will arrive in more intense storm events.
Prolonged periods of wet weather increase water pooling and pressure, making an asset failure more likely. The effects of vegetation on soil and rock slopes can also be dramatic. Drains can get blocked or damaged and, ironically, excessive vegetation removal can also destabilise some delicate earthworks, so it all needs careful management by engineers who know what they are doing.
Every aspect of engineering involves risks which must be understood, prioritised and moderated in order to utilise resources appropriately. The strategy to manage earthworks includes the need to continually develop better technology to make best use of the resource available, reduce cost and steadily evolve more efficient methods for controlling risks. New technology can help – drone inspection and intelligent asset monitoring and reporting to target the interventions required to avoid failure, for example.
Task force
As we report elsewhere in this issue, a comprehensive review of Network Rail’s earthworks management, by a task force led by Professor Lord Robert Mair, has recently reported that surface and sub-surface water management is probably the single most important factor in determining if, when and where an earthwork failure will occur, although the task force did acknowledge that the prediction of precise failure locations is almost impossible.
Today Gerry is the director and owner of CIL Geotechnics Ltd, offering design and consultancy services to a wide range of clients in many areas within the railway industry, providing expert witness and independent assessment, along with structural, geotechnical and drainage design and Contractors Engineering Manager, Principal Designer support.
