High Speed One renewals programme

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High Speed One (HS1), originally known as the Channel Tunnel Rail Link, is reaching an interesting point in its history. Section 1 of HS1 opened in September 2003, running for 74 kilometres (46 miles) from Fawkham junction, near Gravesend in Kent, to the Channel Tunnel. High-speed services from France and Belgium then joined the conventional network and ran through to Waterloo.

To complete the line, Section 2 opened for business in November 2007, making up a total of 109km (68 miles) of 300km/h (186mph) high-speed railway which runs to the transformed St Pancras International we know today.

The whole route was designed and built based on French experience but adapted for the UK. Whereas the main British rail network is modern only from the track formation upwards, roughly speaking, with the basic infrastructure being mainly Victorian in design and construction, HS1 has the advantage of having recently-designed structures, embankments, cuttings and drainage that behave themselves very well by comparison with most similar railway assets elsewhere in the country.

HS1 Ltd holds the concession from the Government to operate, manage and maintain the high-speed railway infrastructure until December 2040. In July 2017, HS1 Ltd was acquired by a consortium comprising of funds advised and managed by InfraRed Capital Partners Limited and Equitix Investment Management Limited.

The railway infrastructure and three of the stations are contracted to be maintained, operated and renewed by Network Rail (High Speed) Limited. The three stations are St Pancras International, Stratford International and Ebbsfleet International. One of the key route performance requirements is that the delay minutes per train be five seconds or under.

Routine maintenance

Network Rail (High Speed), an organisation with over 400 staff, has the specialist knowledge to maintain a high-speed line with French high-speed switches and crossing. The infrastructure manager works towards the asset management objectives of safety, availability and cost, as set by HS1 Ltd.

There is a small team of track staff that make up the track engineering and maintenance divisions. The key track maintenance activities are inspections, componentry changes and heavy mechanical interventions such as tamping and grinding. For a high-speed line, the track geometry needs very tight tolerances. As an example, the line speed of 300km/h requires the vertical alignment (top) to be maintained to 9mm tolerance and the three-metre track twist to 6mm tolerance, which are tighter or equivalent to the construction standard for the classic network, ±10mm and ±6mm, respectively.

The tamping campaign also has a limited window due to weather and risk. Traditional long-wavelength tamping occurs in April and the short-wavelength geometry correction, also known as sprinter tamping, takes place in September to deal with localised defects that must be rectified quickly before they deteriorate into actionable faults.

Grinding is an important activity for geometry and wheel/rail interface management, in terms of ride comfort, RCF (rolling contact fatigue) and noise. RCF is a particular problem with freight and new rolling stock.

Time for renewal

Due to the normal deterioration of the track asset due to ageing, it is coming to the point where a serious amount of heavy maintenance or renewal will be required. A renewal strategy is being formulated and renewal plans refined as deterioration rates and failure modes become apparent. At the same time, maintenance strategy is evolving and being adapted to suit. Whilst technologies and processes are adopted, new associated competencies have to be developed for the team and new plant and tools product-approved to keep up with the changes.

One example is the current need for the replacement of a section of rail, typically an 18-metre length roughly once a month somewhere on the route. Until very recently, such rail replacements were required only about once a year. Head defects such as squats or failed insulated block joints (IBJs) are typical drivers of such works.

Rail-head damage may be caused by ballast flying up in the train slipstream, landing on the rail head and being run over by train wheels. More typical is damage caused by snow and ice on the rail, termed ice pitting, slightly different in appearance but equally harmful and specific to high-speed rail. Rail grinding and possibly rail changing become necessary to cure these faults.

Another example is the need to deal with poor track quality at track stiffness transitions. These occur at the change points between slab and ballasted track, at the ends of bridges and viaducts and even where the track passes over under-track crossings.

Deterioration can also occur in the highly canted curves found on some sections of the route (up to 160mm). These sections have tended to move under traffic and, like the stiffness transitions, necessitate extra tamping and realignment work. This extra tamping results in increased ballast damage that is shortening the life of the ballast in the affected areas.

Further problems arise where rail welds are proud of the rail table for any reason. A height difference of more than 0.5mm on the high-speed line will cause voiding under the adjacent sleepers. If not arrested, this deterioration develops and spreads as train wheels respond by vibrating and causing forces on the rails ‘downstream’ of the weld.

Damaged by ice.

Damaged by ice.

40-year plan

All of these issues mean that the overall level of asset degradation now requires the maintainer to consider responding in an alternative way, and it is therefore tailoring its approach accordingly. They also indicate a future requirement for heavy maintenance and the early development and implementation of HS1’s first renewals programme.

Network Rail (High Speed) is working on the development of a 40-year renewals programme. HS1 is regulated very differently from the Network Rail infrastructure and, for HS1, Control Period 3 (CP3) begins in April 2020. While the main renewal effort is to begin in CP3, there are a few minor track renewals taking place earlier on some parts of the HS1 infrastructure.

An early site is the St Pancras S&C layout, which was constructed to the old RT60 design that has been shown to have inherent problems. Although only around 10 years old, the track maintenance team has recently ordered spares based on accumulated experience from the classic network that these units have an average service life of only eight to 15 years, depending on tonnage and speed.

The plan is for renewals at St Pancras to commence with one S&C unit in 2018 and then continue at a rate of three per annum from 2019 until the whole layout has been covered. The renewals are expected to be like-for-like, but taking advantage of the improvements that Network Rail has made to the underlying design, for example by using crossings that embody the revised and improved design of casting now available.

Network Rail (High Speed) also maintains some of Eurotunnel’s infrastructure at Dollands Moor, which is older than the rest of the route. It is planned that the first full track renewals should take place there. A 1-in-24 vertical 113A crossover, dating back to 1990, is to be the first complete renewal. It is suffering from damage to the common crossing, track geometry quality issues and degradation of fishplates.

The renewal programme in CP3 is to include the use of a high output ballast cleaner (HOBC) on Section 1. Principally, this will be to deal with the deteriorated ballast on the highly canted sections where a large amount of tamping has taken place. The challenge for this is the approval of equipment as the HOBC has not been used previously on HS1.

Looking elsewhere

This is not the sole area where the distinction between HS1 and the main Network Rail network comes into play. HS1 is under very much greater pressure to keep the line open to traffic at all times. There is no possibility of blockades, for example, as can be employed at times elsewhere. These kinds of factors mean that renewals on the route require a different approach than that used by Network Rail on the rest of the network.

HS1 is therefore working with a number of possible suppliers besides Network Rail’s own Infrastructure Projects track team, with the intention of going out to competitive tender for the works at the appropriate time.

Few UK contractors have yet had experience of renewing high-speed railway track, and this has to be seen as a great opportunity for gaining experience and building a reputation in this kind of work. In addition, of course, there is a major workload ‘up for grabs’ in the CP3 renewal programme.

While all this is under consideration, there is also the matter of track standards for HS1. It is now time for a review and revision of the standards, to bring them into line with evolving modern practice.

HS1 has been in discussions with European consultants that have extensive knowledge and practical experience of high-speed rail systems in their own countries and elsewhere. The intention is to work with them to update standards for HS1 in time for the standards to be utilised during the CP3 renewals programme.

With the development of the 40-year renewal plan, and with new technology being sought out and applied for the infrastructure manager to become more efficient in maintaining the asset, including the upskilling of staff, it is an exciting time for HS1 and all at Network Rail (High Speed).


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This post first appeared on Rail Engineer