03.04.14
Earthwork improvements ‘unlikely’ to meet modern criteria
Network Rail’s ongoing earthwork improvement programme is “unlikely” to achieve “modern criteria” in the foreseeable future, a new report from the Rail Accident Investigation Branch (RAIB) has revealed.
In response to six landslips which occurred on Network Rail infrastructure between June 2012 and February 2013, RAIB undertook a ‘class investigation’ into earthwork issues related to land neighbouring the railway and to risk management during adverse weather.
RAIB did add that many of Network Rail’s inherited earthworks were constructed with steeper slopes –more susceptible to landslips – than would be achieved with modern design procedures. But it says: “Network Rail’s on-going earthwork improvement programme is unlikely to achieve modern criteria in the foreseeable future.”
However, the independent body found that in some circumstances, key information provided by specialist staff examining earthworks is not considered when the slope management strategy is determined during evaluation.
The report said: “There is a lack of clarity about who should be carrying out visual checks for risks which can develop on neighbouring land between examinations which take place at intervals of up to ten years. The mandated process for collecting information about neighbouring land is, in parts, difficult to implement and not usually followed.”
RAIB stated that technological developments could offer means of improving this data collection, but it did concede that the location and timing of landslips is difficult to predict although they are almost always triggered by relatively high rainfall.
The landslips, which the report focused on, occurred at Loch Treig (near Tulloch) on 28 June 2012, at Falls of Cruachan (on the line to Oban) on 18 July 2012, at Rosyth (near Edinburgh) on 18 July 2012, at St Bees (Cumbria) on 30 August 2012, at Bargoed (South Wales) on 30 January 2013 and at Hatfield Colliery (South Yorkshire) on 11 February 2013.
However, since then, there have been a number of major landslips caused by adverse weather conditions. For instance the weather-beaten line at Dawlish– which saw around 80m of sea wall destroyed by stormy seas and high tides – has been further handicapped by several severe landslips during the engineering improvement works.
As the RAIB investigation was taking place, Network Rail introduced a new process which takes account of ground saturation and (in addition to likelihood) the possible consequence of a landslip.
As a consequence of the accidents under investigation, the RAIB has made five recommendations addressed to Network Rail, relating to improving management of earthwork and drainage risk arising from neighbouring land; considering all information provided by examiners when undertaking evaluations; and enhancing the new adverse weather risk management process.
In response to the report, a Network Rail spokesperson said: “With extreme weather events becoming more and more frequent, a greater focus on these areas is key to our plans over the next five years, with hundreds of millions of pounds set aside specifically for investment and better management of our earthworks and embankments.
“We will take on board RAIB’s recommendations and take any actions deemed necessary.”
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