Analysis: Preparing for the perfect storm

04/09/2020 | RICHARD HAYES

Following the Stonehaven rail disaster, highways industry expert and former chief executive of the Institute of Highway Engineers, Richard Hayes (pictured), discusses some of the engineering and safety issues around landslips.

The recent rail tragedy near Stonehaven in Scotland where three people were killed was the first fatality on the rail network for over 13 years. The last being at Grayrigg in Cumbria in 2007.

The incident seems to be the result of a landslide across the mainline southwards from Stonehaven station following a period of heavy rain. Sadly it follows a report by the rail regulator, the Office of Rail and Road (ORR), in July this year, which criticised the approach taken by Network Rail to tackle an ever increasing number of landslips and rail tracks being washed out and its reaction to the effects of climate change.

The ORR noted: 'The vulnerability of some assets to the challenges of climate change and more frequent extreme weather events was illustrated in 2019/20. The year saw substantial increases in flooding events, earthwork failures and trains striking trees on the line.'

Fortunately, there has yet to be, as far as I can gather, any serious injury to road users from landslips and road collapses although there are many dramatic pictures on the internet of such occurrences. Fatalities due to falling trees are also unfortunately more common.

Where landslips or collapses often occur, and this compares with the rail network, are on roads crossing hilly terrain or on coastal routes and these road layouts have been in place for many years. As with railways they were often constructed in Victorian/Edwardian times when earthwork embankments and slopes were less well designed. The UK motorway network has suffered only a few small incidents as most of its embankments were designed more recently, have less severe slopes and often include drainage systems to maintain and stabilise them.

I have been directly involved in dealing with such landslips: on the Morpeth to Rothbury road in Northumberland and the A431 at Kelston near Bath, which both led to lengthy road closure and costs of several million pounds to repair in addition to the disruption to the public.

During 2020 we have seen a major route - the A83 in Scotland, affectionately referred to as the ‘Rest and Be thankful’ - suffer a closure along with its normal diversionary route the Old Military Road in August, when a hillside slippage caused over 6,000 tonnes of material to fall across these highways.

The August weather also caused a major collapse on the B4355 at Lloyney, near Knighton, Wales when a culvert was washed away.

In such situations, a major clearance operation is required while geologists and engineers consider how to stabilise the hillside to prevent further incidents.

Work on the A83 at Rest and Be Thankful.

The response to such incidents causes a major headache for highway authorities and it is such organisations that suffer the most when they occur with vital routes being unavailable for several weeks in some cases and the cost of the repair having to be borne initially by the local taxpayer. It should be also considered that drought conditions, as we encountered in March and April, can also lead to unstable ground conditions as the terrain dries and shrinks.

Is it possible to prevent these problems?

Any changes in ground conditions are exceedingly difficult to predict but quite often, and particularly in urban situations, the cause is easily identified where washout of foundation material has occurred due to a burst or damaged pipe. Exceptionally in 2012, a section of Whinlater pass in Cumbria collapsed due to a failed badger underpass.

However in the upland areas the cause is often a landslip. Sometimes, as with the A83, this is caused by heavy rain affecting the stability of embankments. But with no monitoring systems in place, they can occur at almost any location. Often the first signs of impending disaster are longitudinal cracks on the edges of carriageways.

Because of continuous rain, the surface water seeps and softens the surrounding embankment, lowering the cohesiveness and fictional angle and weakening the self-stableness of the embankment.

Stabilisation can be improved by flattening the slope, which results in a reduction in weight making the slope more stable; soil stabilization; providing lateral supports by piles or retaining walls or grouting or cement injections into special places.

All these solutions are expensive and require several weeks to undertake and can lead to major disturbance to the travelling arrangements in the area.

With the changes to the UK climate we are experiencing more of these incidents and it is timely perhaps to consider how some can be foreseen and prevented.

One simple method is to ensure adequate vegetation on the embankment. Slopes with no vegetation or cover are especially vulnerable to erosion issues.

The most effective, natural way to control soil erosion on slopes is to plant vegetation. Not only will vegetation help to slow down raindrops as they fall, but also the roots of the plants will also help to hold the soil together, making it harder for water to wash it away. This method should not include the planting of trees, which can have a de-stabilising effect and should be removed if possible.

Other methods can include slope drainage systems, soil nailing and slope facing mesh systems. These solutions are often carried after a slip has occurred.

How can we predict?

As with most methods of good maintenance it is important to know where such situations are likely to occur. A few simple questions to consider, remembering of course of the duty to keep roads free from any debris, falling from an embankment:

  • How many embankments or slopes over, for example, two meters in height do you have on your network?
  • Do you know who owns the embankment or cutting?
  • What is its condition, vegetation slope?
  • Are regular inspections being undertaken?

It will be challenging for many authorities to add this to their asset management policies and plans but as with many aspects of road maintenance the effects of changes in the UK climate require us to review our methods or do nothing and wait for the next storm and its consequences.

Highways InProfile

latest magazine issue
Highways jobs

Senior Highway Engineer (Development Management)

£42679.0000 - £50211.0000 per annum
Senior Highway Engineer (Development Management)Permanent, Full Time£43,960 to £51,718 per annum*Location
Recruiter: Essex County Council

Project Manager (Major Projects)

£44,711 - £47,754
Are you an experienced project professional or engineer with looking to take the next step in your career? Halifax, West Yorkshire
Recruiter: Calderdale Metropolitan Borough Council

Senior Civil Engineer - Roads

£45,894 - £54,952
Are you an experienced engineer looking to support the Scottish Government’s national objectives. Scotland
Recruiter: Transport Scotland

Senior Civil Engineering Technician

Grade 7 £29,093 to £32,654 per annum
We are looking for a flexible individual who has the ability to meet targets and analyse and resolve complex technical problems and formulate a design Durham
Recruiter: Durham County Council

Project Team Manager

£55,147 to £60,676 per annum
We are pleased to be able to offer an opportunity for a role as Design Team Manager Norwich, Norfolk
Recruiter: Norfolk County Council

Clerk of Works

GRADE 08 (£37,938 - £41,511)
Warrington is one of the most successful towns in the country Warrington, Cheshire
Recruiter: Warrington Borough Council

Assistant Projects Engineer

GRADE 06 (£29,093 - £32,654),GRADE 07 (£33,366 - £37,035), GRADE 08 (£37,938 - £41,511)
Warrington is one of the most successful towns in the country Warrington, Cheshire
Recruiter: Warrington Borough Council

Principal Engineer - Traffic Management

£45,718 - £48,710 per annum
At Bath & North East Somerset Council we have one overriding purpose – to improve people’s lives. Bath, Somerset
Recruiter: Bath & North East Somerset Council

Vehicle Technician - Improver

£28,624 - £30,060
Transport Services is responsible for all aspects of transport and related services Huddersfield, West Yorkshire
Recruiter: Kirklees Metropolitan Council

Principal Engineer - Highways Safety

£37,035 - £45,718 (plus £3000 Market Rate Supplement, reviewed annually)
To help achieve our ambition we are looking for a Principal Engineer with the following skills and experience to join the team. Huddersfield, West Yorkshire
Recruiter: Kirklees Metropolitan Council

Part Time Caretaker and General Hand

Up to £25081.00 per annum + Full Time Equivalent
Part Time Caretaker and General HandPermanent, Part Time£25,081 Per Annum, Full Time Equivalent, equal to £13.00 per hourLocation
Recruiter: Essex County Council

Programme Delivery Office Administrator

Grade 9 £31,344 - £33,253 per annum
At Derbyshire, we have been on a journey to transform the way we deliver highway services to make them fit for the future Derbyshire
Recruiter: Derbyshire County Council

Support Officer - Highways Asset Management Systems

£31,586 - £34,314
We are a forward-thinking organisation dedicated to maintaining and improving our highway infrastructure. Lincolnshire
Recruiter: Lincolnshire County Council

Highways Officer (East)

£31,586 - £34,314
This is an exciting opportunity in an ever-evolving service that is both challenging and rewarding. Lincolnshire
Recruiter: Lincolnshire County Council

Rights of Way Assistant

£28,797 - £30,708
Within the Highways Directorate we are looking to appoint enthusiastic, customer focused and experienced person to join the Service. Darley Dale, Matlock
Recruiter: Derbyshire County Council

Principal Transport Planner (Strategy)

£46,731-£49,764
We are looking for an experienced professional to join North Northamptonshire Council as a Principal Transport Planner (Strategy). Sheerness House, 41 Meadow Road, Kettering moving to Haylock House, Kettering Parkway, Kettering NN15 6EY, United Kingdom
Recruiter: North Northamptonshire Council

Electrical Engineer

Grade 9 £34,314 to £37,938 - Grade 10 £37,035 to £40,476 - Grade 11 £39,513 to £43,693 - Grade 12 £42,708 to £46,731 p.a.
The Construction Consultancy Services (CCS) team provide client-side construction consultancy services across a range of professional disciplines to d Durham
Recruiter: Durham County Council

Senior Development Management Engineer

£37,938 - £44,711
In line with our One Coventry Values, we want to ensure that our communities are represented across our workforce Coventry, West Midlands
Recruiter: Coventry City Council

Head of Highways

£66,366 - £85,284 pa
Highway Operations is a large division within the Planning, Growth & Infrastructure. Enfield (City/Town), London (Greater)
Recruiter: Enfield London Borough Council

Director Highways, Transport & Waste Management

up to £120k
There for Nottinghamshire. There for each other. There for you. Nottinghamshire
Recruiter: Nottinghamshire County Council
SUBSCRIBE NOW

Latest Video

Subscribe to Highways today to ensure you keep your finger on the pulse of everything happening in the UK road network throughout the year.

SUBSCRIBE NOW