Railway Earthworks After Extreme Weather: Why Early Intervention Matters

Periods of prolonged dry weather followed by sustained or intense rainfall can place additional pressure on railway cuttings and embankments. For asset managers, contractors and engineers, this means paying closer attention not only to major slope instability, but also to the smaller changes that can develop at the surface.

Network Rail manages more than 190,000 earthwork assets across approximately 20,000 miles of track, with many cuttings and embankments dating back more than 150 years. Managing such an extensive and ageing portfolio requires a combination of inspection, drainage management, vegetation management and timely intervention.

One area that can sometimes be overlooked is the condition of the earthwork surface itself.

Loss of vegetation, exposed soil, localised erosion, sediment movement and changes to surface drainage may appear relatively minor when considered individually. However, these can be early indications that the condition of an earthwork is changing.

Shiran Amunugama, Managing Director of British natural-fibre geotechnical specialist Salike® Geotechnics, believes this period between a slope performing normally and requiring significant intervention deserves greater attention.

“Infrastructure is often discussed in quite binary terms — an asset is performing or it has failed. In practice, there can be a considerable period between those two conditions, and that is where good asset management can make a real difference.”

“Something relatively small, such as vegetation loss, an exposed area of soil, localised erosion or a drainage issue, does not necessarily mean an earthwork is unstable. But identifying and managing these changes early can help prevent relatively manageable problems from becoming much larger ones.”

Vegetation also has an important role to play. Appropriately established vegetation can help protect exposed soils from direct rainfall, interrupt surface runoff and contribute to near-surface stability through developing root systems.

There are circumstances, particularly following construction, regrading, vegetation clearance or remedial works, when an earthwork may also experience a vulnerable establishment period before vegetation becomes sufficiently developed.

Natural-fibre erosion-control systems can have a useful role during this stage.

Salike® supplies coir netting, erosion-control blankets and other natural-fibre geotechnical systems for infrastructure and environmental projects. Rather than replacing structural slope stabilisation or drainage measures, these systems can be specified to help protect vulnerable surface soils and support vegetation while it establishes.

Shiran added:

“Natural-fibre systems are not the answer to every geotechnical problem, and they should never be presented as such. Their value comes from understanding where they have a genuine engineering function.”

“Where the requirement is to protect a vulnerable surface, manage erosion and provide the conditions for vegetation to establish, properly specified natural-fibre systems can make a valuable contribution.”

As Britain's infrastructure adapts to more variable weather conditions, the emphasis is increasingly likely to move beyond responding to failure and towards recognising vulnerability earlier.

For railway earthworks, the question after an extreme period of weather is therefore not simply whether a slope remains standing. It is also whether drainage is functioning, vegetation is establishing successfully, exposed soils are being protected and relatively small signs of deterioration are being addressed before they develop further.

Sometimes the most effective infrastructure intervention is the one made before a major problem becomes visible.

About Salike®
Established in 2015, Salike® is a British engineering-led supplier of natural-fibre erosion control and geotechnical systems. The company supplies solutions for erosion management, slope protection, river restoration, habitat creation and environmental infrastructure projects in the UK and internationally.