Connecting and improving: towards a more stable railway

For seven years now, ProRail has been calling on Deltares' expertise in underground systems to make the 7,000 kilometres of railway in the Netherlands future-proof. ProRail needs this knowledge to realise its own ambitions: connecting, improving and making the railways more sustainable in the most efficient way possible. This is not easy with a tight labour market and construction costs that have risen significantly, while climate adaptation is also becoming an increasingly important aspect.

Multi-year collaboration

‘That is why ProRail set up a multi-year collaboration with various knowledge institutions such as TNO, TU Delft and Deltares, so that together we can look further ahead to see what knowledge we need to develop in order to guarantee solid business operations in the future,’ explains Michelle Spaas. Michelle is now Programme Manager Innovation and was the driving force behind these knowledge alliances.

Together with Arjen Zoeteman, policy advisor for Research, she welcomes Deltares experts Joris van Ruijven and Bruno Zuada Coelho to the Railcenter in Amersfoort. Here, ProRail employees, contractors, engineering firms, transport companies and knowledge institutions meet for meetings and events focused on knowledge sharing.

Joris van Ruijven is the coordinator for ProRail's knowledge questions at Deltares, and Bruno Zuada Coelho is an expert in dynamics and the substantive conscience for a large number of rail-related questions.

Arjen recalls their meeting on a Swedish 'measurement train', where the influence of the subsoil structure on the condition of the track was investigated for the first time. ‘It was a real eye-opener to see the influence of the subsoil on our infrastructure.’

Knowledge close at hand

Michelle emphasises the importance of sustainable collaboration with a knowledge institute such as Deltares: ‘Working together as strategic partners yields more than engaging parties on a project-by-project basis. We don't have to keep explaining how the rail system works, and we can never know as much about the subgrade as Deltares does.’

Arjen sees that this form of collaboration offers more scope to challenge each other: ‘What does Deltares see in other infrastructure networks that could also benefit us? What do we need to take into account in the future?’

Deltares and ProRail have built up a basis of trust, says Michelle. ‘We are increasingly speaking the same language, are results-oriented and are working on applying knowledge.’

Joris adds: ‘We are closely involved in the knowledge questions and, because we have been working together for many years, we can ensure that relevant knowledge is put into practice. In this way, we contribute to solutions for questions about the safety and availability of the railways and the social costs and benefits thereof.’

Challenges

These knowledge alliances are not a luxury, as Michelle and Arjen explain when they outline the challenges facing ProRail as a rail network manager. ‘Facilitating the growth in the number of train passengers and freight transport, for example,’ says Michelle.

‘The government is also asking us to make our operations more sustainable, both in terms of energy and material use, if we want fewer disruptions and train cancellations and better connections within Europe. At the same time, we have to renew, manage and maintain existing railways, digitise our working methods and reduce costs. And all this with fewer and fewer people and a future in which there will be fewer technicians on the labour market.’

Working together as strategic partners yields more results than engaging parties on a project-by-project basis. We do not have to explain how the rail system works over and over again, and we can never know as much about the subsurface as Deltares does.

Michelle Spaas, programme manager Innovation at ProRail

Stable railways

Incidents such as subsidence of the subsurface causing railways to sink are a major headache for ProRail. This can slow down trains or prevent them from running altogether, as was the case with the recent subsidence at various locations on the railway between Utrecht and Eindhoven.

Arjen: ‘And two years ago, subsidence in Zeeland meant that trains could only travel at 40 kilometres per hour. This is a risk, also for a future with more extreme weather. That is why we want to know how our railways and the ground interact and how this can be improved.’

Recouping costs

Deltares is investigating this in the RESET programme, together with Delft University of Technology. In RESET, Deltares is applying its expertise in the field of dyke safety and its experimental and digital facilities.

Joris: "We are looking at the behaviour of groundwater in the railway embankments, the effect of dry periods and the way in which a moving train puts pressure on the railway embankment. We help translate the results of the scientific research and the models developed by TU Delft into practical applications."

The first practical tests were conducted between Delft and Schiedam, with a second series to follow shortly. This location was chosen because ProRail had indications that this railway line needed reinforcement.

Joris: ‘Here, RESET has paid for itself on an eight-kilometre stretch of track. Measurements taken on the track, among other things, enabled us to conclude that more trains can run on the railway line than expected.’

What does Deltares see in other infrastructure networks that could also benefit us? What do we need to take into account in the future?

Arjen Zoeteman, policy advisor Research at ProRail

Arjen explains that the composition of the subsoil can vary enormously even over a small area. ‘In the consortium, we are developing knowledge about the subsoil in combination with the stability of railway tracks. Once we understand the subsoil, we can draw up new design standards for our assets with Deltares.’

And then there is the challenge of climate-adaptive railways, adds Bruno. ‘What effect do prolonged drought and extreme rainfall have on the stability of railway tracks?’

Vibrations from train traffic

To meet the growing demand for housing, construction is increasingly taking place closer to the railway. To prevent residents from being bothered by vibrations, even if train traffic increases in the future, ProRail asked a consortium of Deltares, TU Delft and TNO to map out how and where railway vibrations occur and which measures are effective where and when. The aim is to find affordable and reliable measures, as almost 1.3 million people in the Netherlands live close to the railway.

Deltares is building the Railway Vibration Emission Model (STEM) for this purpose. Bruno: ‘This brings together the vehicle, track and subsoil and shows precisely how different factors influence each other in space and time.’

Together with engineering firms and construction companies, ProRail is developing innovative solutions to reduce vibrations, such as introducing bacteria into the subsoil to “stiffen” it.

‘Our model shows where this works and where it doesn't,’ says Bruno. ‘This means you don't waste time and money and can take steps towards effective solutions.’

Complex

A major challenge here is obtaining data that provides sufficiently reliable answers for ProRail's rail network. Bruno notes that this data is not always available, accessible and standardised among the partners.

'What data is available, what information is still needed? How do we utilise the value of existing data? And how do we use it to update our models? With models, we can predict situations and still provide good answers when little data is available.‘

Retrieving data for these types of models is particularly complex, says Bruno. ’The accessibility of the railway, arranging to be able to take measurements safely along the tracks, the hours and costs involved are enormous.'

‘There are kilometres of fibre optic cables along the track,’ says Arjen. ‘We can use these cables as sensors: they measure vibrations and noise and thus deviations in the track, rolling stock or environment.’

In addition to other data, Bruno finds fibre optic monitoring helpful and promising in determining where ProRail needs to reinforce tracks. ‘This helps us if we want to know the critical train speed. When a train travels at a certain speed, it creates waves that can cause deformations in the subsoil. And that leads to problems in soft soils such as those in the Netherlands.’

Making choices

Joris and Bruno therefore emphasise the importance of making choices. ‘Do we want to put a lot of energy into developing general knowledge about the subgrade of the railway, or more specific knowledge that ProRail can apply directly? We have to weigh this up continuously,’ says Bruno.

‘For track stability, the strength of the subgrade is important, and for vibration nuisance, stiffness is important. There is a correlation, but it is not the same thing. What information allows the model and, with it, ProRail's applications to work properly?’ Data alone is useless; you have to know what you are looking for, Michelle nods.

‘There are kilometres of fibre optic cables along the track,’ says Arjen. ‘We can use these cables as sensors: they measure vibrations and noise and thus deviations in the track, rolling stock or environment.’

In addition to other data, Bruno finds fibre optic monitoring helpful and promising in determining where ProRail needs to reinforce tracks. ‘This helps us if we want to know the critical train speed. When a train travels at a certain speed, it creates waves that can cause deformations in the subsoil. And that leads to problems in soft soils such as those in the Netherlands.’

Making an impact

By working closely with ProRail's geotechnical engineers, engineering firms and construction companies in the research, Deltares ensures that the knowledge gained can be put into practice. Geotechnical engineers use the information and recommendations provided by Deltares to refine the design and maintenance standards, explains Arjen.

Michelle: ‘The STEM and RESET programmes are designed in such a way that stakeholders can get involved at an early stage and are consulted about the usability of the models during their development.’

Future

How do the partners view the future? Michelle takes a positive view of the digitisation of management and maintenance work: ‘Predictive maintenance allows us to identify where problems will arise and where intervention is therefore needed first. We need information and data for this.’

She also hopes that developments to improve the interconnection of European railways will continue. ‘This will help us realise our ambitions for connectivity and sustainability.’

Arjen adds: ‘Working together to maximise and grow the greenest and most efficient mode of transport we have, rail traffic. This is only possible with safe and reliable tracks and railways.’

Joris emphasises the importance of actually incorporating the knowledge developed into ProRail's digital work process. ‘So that we can really capitalise on the value of the knowledge and models developed.’

Bruno points to the importance of a digital twin of the entire Dutch rail network. ‘This allows you to bring together all of ProRail's tasks, from track stability to vibration nuisance and climate adaptation, in a single model. This helps to quickly assess the consequences of choices. Only then can you really see what the choice for more, faster, heavier and longer trains means.’