Context

Ensuring structural integrity during major sea wall redevelopment in Wales, the Cambrian Coast railway runs on a six-span concrete viaduct at Barmouth in the United Kingdom. When nearby coastal defence works potentially threatened the stability of the structure, DYWIDAG implemented the first commercial application of Worldsensing GNSS Meter technology to help safeguard this critical Network Rail asset. 

As part of a redevelopment scheme at Church Street in Barmouth, Alun Griffiths Ltd carried out significant piling works and rebuilt a sea wall immediately adjacent to the railway viaduct. These activities created a risk of settlement-induced movement in the viaduct piers, requiring a monitoring system capable of providing both short-term alerts and long-term trend data in a constrained environment.

Solution

Providing consistent monitoring at the site presented several challenges. The workspace around the viaduct was too restricted for a traditional 3D target monitoring regime, and an Automated Total Station (ATS) was not feasible because changing work zones would frequently obstruct sightlines to the structure. A manual survey approach would also have significantly increased project costs due to the long duration of the works. In addition, the monitoring system needed to operate within site compound constraints, meet power requirements, and minimize potential security risks.

To address these challenges, the DYWIDAG SHM team implemented a wireless monitoring solution that combined long-term structural trend analysis with immediate safety alerts. The project marked the first commercial deployment of Worldsensing GNSS Meters in the UK, which provided high-precision settlement data for the viaduct piers without the clear sightlines required by optical monitoring systems. 5 GNSS Meters with rovers and one with base were deployed.

“By pioneering the first commercial deployment of Worldsensing GNSS Meters, we’ve effectively removed the ‘line-of-sight’ barrier that has historically hindered complex rail projects. This wasn’t just about monitoring; it was about proving that wireless, satellite-based precision is the future of structural health for restricted urban environments.”

Robert Paterson, Regional Director, DYWIDAG

Because the works were critical asset owners, the team also installed 5 Worldsensing event detection Tiltmeters mounted on 3-meter beams to detect any rotation of the bridge columns caused by potential foundation movement, enabling rapid safety alerts. The monitoring equipment was installed and secured to the viaduct by qualified personnel using a mobile elevating work platform (MEWP).

Benefits

By utilizing this wireless, remote monitoring solution, the project achieved continuous assurance, capturing both short-term movements and long-term settlement to provide confidence throughout the work. The event detection system enhanced operational safety by giving project teams fast-response alerts if any movement occurred, ensuring work could proceed with minimal risk. 

All data was accessible through a dedicated portal, allowing both the contractor and client to view, interrogate, and analyze information in real time. This automated approach also improved cost efficiency by eliminating the significant expenses associated with manual survey methods.

Advantages

• Wireless independence: The system bypassed the power requirements and security risks associated with automated survey stations.
• Rapid deployment: The entire system was installed and secured in just two days.
• Non-line-of-sight capability: Unlike optical systems, the GNSS Meters remained effective even when sightlines were blocked by construction activity.
• Dual-layer protection: The combination of Tiltmeters in Event Detection mode and GNSS Meters for long-term trends ensured comprehensive structural oversight.