As a railway civil engineer, one of my greatest concerns related to the condition of the earthworks on my patch. A failure of an embankment or cutting slope could cause severe risks to the safety and operational integrity of the railway under my care.
For engineers on the UK rail system, this is probably a greater issue than for those of many other countries. Britain pioneered the development of modern railways in the nineteenth century and suffers for this in many ways. Our tight structure gauge is well known, but is not the only difficult legacy that we have inherited from our Victorian forebears. We also have to manage other challenges resulting from the fact that our railways were built very early in the engineering learning curve.
Not least among these challenges are those relating to earthworks. These include earth and rock slopes that were constructed at angles far steeper than hindsight shows us they really ought to have been, embankments formed from materials of doubtful and very mixed quality, and railway corridors narrower than desirable. The drainage arrangements originally constructed were also often less than adequate, and over the passage of time many of them have become obstructed, neglected or forgotten.
As a consequence, the management of banks, cuttings and rock faces on the national network has always been a challenge, and disruptive failures have been too common.
Tony Wilcock is head of civils asset management (geotechnical) for Network Rail, so he has the task of managing and improving this situation. He acknowledges that, in general terms, Railtrack did not inherit good asset records of earthworks and drainage from British Rail, nor was there what would now be recognised as a systematic regime of inspections in place for these assets at the time of the handover. Since then, under both Railtrack and Network Rail, great efforts have been made to change this. About ten years ago a formal inspection regime was introduced for earthworks (including rock cuttings) similar to that which was well established for other structures such as bridges, tunnels and retaining walls.
An earthwork is recognised as being anything of at least 3 metres height or depth, and each one is divided into lengths of five chains (about 100 metres) for inspection and records purposes. The ongoing inspection frequencies for each site are determined according to the condition found. The worst sites are now the subject of an annual routine inspection regime, better ones being inspected less frequently. Of course, if an earthwork deteriorates seriously, annual inspection may not be sufficient and it may be made the subject of much more frequent inspection and monitoring until its condition can be rectified, just as would occur with a bridge that was in a serious state.
About five years ago, Network Rail decided to adopt an asset scoring system for earthworks. This was designed to support the management of the large earthwork asset inventory by making it easier to compare earthworks of different types and by ensuring consistent marking of common features irrespective of the earthwork type. For example, there are now standard ways to report animal infestation or vegetation problems for cuttings and embankments or any other earthworks. This is extremely useful to the company and its stakeholders when considering priorities and funding for the network as a whole, taking account of all asset types.
Detailed information is collected about each 5-chain length of earthwork and entered into a handheld data logger. Information collected includes height, slope, animal activity, vegetation present, earthwork drainage (if any) and details of any failure indicators. The information entered feeds into an algorithm which generates an asset condition score for that length. Based upon these scores, the assets are categorised as poor, marginal or serviceable and it is this categorisation which determines the future inspection frequency.
Network Rail now has formal earthworks asset data covering the last ten years . Treating each side of the line separately (factors such as height may vary significantly between one side of the line and the other) there are just under 10,000 miles of earthworks, a total 160,000 individual 5-chain lengths. Roughly speaking, there are earthworks on about half the 10,000 route miles of the network. About 90% of them have now been scored under the current system, and the remainder will be included very soon as the inspection regime continues.
Those that have yet to be included will be the structures at lowest risk, of course, as these will be those that are subject to the least frequent inspections.
All this information has borne fruit. The company has been much better able to justify funding for earthworks-related activities as a result of having high-quality asset information in a format consistent with the other asset data it holds, and in CP4 the budget for earthworks has been £450m. This will have enabled remedial works to around 21⁄2 million square metres of earthworks by the time the control period ends.
A similar story to that of earthworks relates to the past inspection of track and structures drainage, and Network Rail recognised this. An integrated drainage programme was initiated, leading to a rapid national survey. It was decided that where possible this should be undertaken by in-house staff as this would enable them to gain valuable first hand understanding of the drainage assets for which they are responsible. In-house resources being unavailable in Wessex, the surveys on this route have been undertaken by WaterFlow.
A training programme was undertaken by MWH UK to give the staff improved knowledge about drainage and give them the required skills in using the data logging devices. These devices are GPS enabled and, like those used for earthworks, require data to be entered in a standard format to ensure complete and consistent data collection. Collected data is fed into a version of the Network Rail’s Ellipse work scheduling tool which has been specially developed for drainage assets. Currently about 80% of the network’s drainage has now been surveyed at a cost of about £3m.
In addition, Network Rail has been undertaking topographical surveys of its network and surrounding lands to enable it to identify high-risk natural slopes adjacent to Network Rail boundaries. Techniques such as aerial LIDAR (LIght Detection And Ranging) surveys are also feeding data into systems such as the water concentration database. This identifies additional risks to the network, such as from external watercourses, drainage ditches or reservoirs on adjacent land. Information is collected in a WERM (Washout and Earthflow Risk Management) database. Work like this will enable the company to extend its risk management beyond the confines of its own land boundaries.
In due course, this work should lead to the management of risks such as those which led to the Loch Trieg derailment earlier this year. In that incident a Class 66 locomotive and 5 bauxite wagons ran into a landslide that had originated in a natural slope outside the Network Rail boundary. Boulders in the washed down material led to the derailment of the train.
All this is enabling the development of a proper five-year asset management plan for track and structures drainage for CP5. It will allow the company to make a credible bid for funding for drainage for that control period, the first time that this has been possible. All track engineers recognise that good and lasting track condition is not possible without a well drained trackbed. However, without a detailed asset record, it has sometimes been difficult to justify and obtain sufficient budget to undertake all the work required.
Network Rail is not doing all of this on its own. The company has been using the resources and expertise of a number of external organisations. Mott MacDonald and Arup have both been involved in assisting in the development of the relevant policies. Amey has the national contract for the examination of earthworks, and employs around seven examinations engineers and about 35 examiners for the purpose.
JBA Consulting holds the asset management database and has been helping to develop
asset data collection systems for Network Rail for about 10 years. Their work has resulted in the current web based set-up using handheld devices for data input.
What has been the outcome of all this in practical terms thus far? Well, since the earthworks asset data collection regime began roughly 10 years ago, and up until this year, there was a consistent falling trend in incidents involving earthworks. The 28 such incidents in 2011-12 was the lowest figure for 7 years. Unfortunately the severe weather conditions of 2012 have caused a reversal of the trend, with about 40 incidents to date this year. Given that rainfall across the UK in April was three times the average for that month, June had double the average and July much the same, this picture is not surprising.
There does seem to be evidence that the climate in the UK is trending towards more extreme weather. Not only do there seem to be more periods of very intensive rainfall, some of them very localised and severe, but also there appear to be more periods of drought. The latter can exacerbate the former by causing cracks and other forms of weakness in earthworks that make them more likely to fail when heavy rainfall does occur.
Network Rail is not leaving things to chance. As well as taking care to thoroughly investigate all incidents itself and learn the lessons from them, and ensuring that they take full heed of any further lessons from other investigations such as those of the RAIB, the company is looking further afield for understanding. Network Rail has been benchmarking its activities against other railway administrations in Europe and elsewhere and Tony considers its approach to be better than most that he has seen.
Work is also being undertaken with other railways in countries where more severe climatic conditions already prevail. One such country is Hong Kong, and Network Rail is actively engaged in learning from the experiences of railway managers there in countering the effects of severe weather.
The results of these benchmarking activities, the lessons learned form failure investigations and the studies of practices abroad are being fed into revised company standards and policies to deliver better future outcomes.
All told, Network Rail is taking a professional and pro-active approach to mitigating risks and improving performance, rather than reacting to incidents. The peak season for earthworks asset inspections is November to April (due to the die back of vegetation), so Tony and his colleagues are going to have a very busy winter.