Repairs competed on iconic bridge as dry weather undermines infrastructure

The recent prolonged dry weather in the UK has not just resulted in brown grass everywhere, it has also affected the stability of a number of buildings and structures around the nation.

As clays and other soils dry out, the resulting loss of volume and of rigidity can cause subsidence and other problems.

In Scotland, a whole street in Coalsnaughton, Clackmannanshire, was evacuated after significant ground movement raised concerns. Residents were moved to temporary accommodation with very little warning.

Just 10 miles away, leading ground engineering and void specialist Mainmark UK has been strengthening the approaches to a landmark bridge after they, too, were affected by subsidence.

The Bannockburn / Telford Bridge, on the A9/130, is a circular arch road bridge designed in the early 19th century by renowned Scottish engineer Thomas Telford, a pioneer of bridges, roads and canals and the first president of the Institution of Civil Engineers (ICE).

Stirling Council appointed Mainmark UK to strengthen the made ground on the approaches to the bridge, which had been impacted by subsidence. The retaining walls had also experienced settlement, which occurs when soil compresses beneath the weight of a structure.

The project highlights the growing challenge facing the UK’s ageing infrastructure, where ground movement, changing weather patterns and increasing traffic volumes are placing additional pressure on roads, bridges and other critical assets.

David Hedley, infrastructure lead at Mainmark UK, said: “Roads in Scotland saw nearly a 25 per cent increase in vehicle traffic between 2020 and 2025. Combined with rising temperatures and increasingly unpredictable weather, this creates a real and growing risk for infrastructure already vulnerable to ground movement.

“Subsidence is not simply a surface defect. It is often a sign that the ground beneath an asset has weakened or shifted.

“By addressing the ground conditions below or on the approach to infrastructure, rather than repeatedly repairing damaged surfaces, asset owners can achieve a longer-term solution that reduces disruption, improves safety and protects critical transport networks.”

Scotland’s ground conditions include areas of soft clay and peaty soil, both of which can be affected by changes in moisture content. During prolonged dry or warmer periods, moisture loss can cause certain soils to contract and shrink, increasing the risk of settlement and structural movement.

This, together with unpredictable weather conditions and combined with heavier use of the road network, can contribute to gradual movement in the subsoil and undermine the foundations of infrastructure.

Mainmark’s work on the £40,000 project only took four days to complete and used targeted resin injection technology to strengthen subgrade soils and re-support the structure without the need for full reconstruction. The approach is designed to be delivered quickly and with minimal disruption, helping to reduce traffic delays while extending the service life of affected assets.

David added: “Infrastructure owners need to actively monitor for warning signs of substructural issues before they develop into major failures. Once bridges, roads or other assets become structurally compromised, the result can be long-term closures, significant repair costs and serious disruption for local communities and road users.

“Proactive ground improvement gives councils and infrastructure managers a way to intervene earlier, stabilise the asset and avoid more invasive reconstruction works.”