Overview

As part of the Transport for Wales rail system, a rolling stock depot, built at Taffs Well, required a bridge to connect it to the rail station. Before building the new bridge a sheet pile wall had to be installed in order to retain earth and other filling material during piling activities.

Monitoring objective

The monitoring system provided by Move Solutions through one of their UK supplier, Korec Group, collects real-time data of the sheet pile wall, 24 hours a day, 7 days a week. The aim is to identify any changes in the behaviour and position of the wall so as to avoid structural failure after its removal.

Monitoring system

The system installed consisted of the following elements:

• 16 Tiltmeters
  • Mounted on 1-meter magnetic tilt beams

• 12 Accelerometers

• • Mounted on magnet mounts

• 1 Gateway

• • Supported by a Backup Power System

The Tiltmeters and Accelerometers were installed along the length of the sheet pile wall to provide comparable data on its position and frequency response of the wall during and after piling works. The sensors were installed using magnet mounts so that they could be easily transferred to different sheet piles afterwards. The SHM Accelerometers provided both thresholds triggered vibration readings and scheduled synchronized readings for remote modal shape analysis via the Move Cloud Platform.

The monitoring system installation was completed in 6 hours: that included the assembly of the Tiltmeters, the Tilt-beams and the SHM Accelerometers to the magnet mounts, which this time was completed on-site due to the short-notice before the installation. All sensors were online and communicating with the Gateway within 20 minutes from its activation.
A backup power system was required for continuous monitoring as the primary one on site was switched off overnight and during the weekends.

The monitoring installation will be in situ for approximately 12 months in total with the sensors being eventually repositioned onto a new sheet pile retaining wall.

Project notes

Transport for Wales manages the whole rail infrastructure in Wales.
The monitoring system sensors were supplied by Korec Group, an official Move Solutions reseller for the UK market.
Dyna-mo Instruments provided the magnetic mount kits, tilt beams and the backup power system. The monitoring devices are powered by a generator during the day, while the backup power system takes over overnight and at weekends. When the generator is switched back on the backup power system recharges from the generator power.

Amey designed the monitoring system, installation location and alarm activation.

Alun Griffiths are the contractor onsite completing the build of the new wall and the removal of the old. They were also responsible for carrying out the system installation.

Conclusion

The structural health monitoring system has provided valuable data and visualization via the Move Cloud Platform of the behaviour of the wall since the start of the piling activities. Significant vibration readings have been able to be directly correlated to the proximity of each sensor to the piling works. It is anticipated that the wall will present a change in its behaviour, which will be observed via the SHM Accelerometers when the wall anchors are cut on the existing retaining wall in Q2 2022.