GEO-Instruments engineers have been working alongside Keller colleagues monitoring the stability of a retaining wall on a major railway project in north London.
A sheet pile retaining wall has been built next to the rail lines to support a vehicle access ramp for the site. The wall is being stabilised using more than 200 multi-strand ground anchors installed in arrays alongside the ramp location.
Working with Keller’s anchoring and stressing specialists, GEO-Instruments installed load cells onto a portion of the anchors to verify loading of the anchors and stability of the wall, making sure the access ramp can be used safely during construction. The sensors use internal electrical resistance strain gauges that record changes in resistance as load is applied.
The load cells have been custom built in the UK to the designed load and accuracy for this project and are capable of measuring loads up to 300kN. In total, thirteen load cells were installed at regular spacings along the monitored area of the wall.
During installation, the sensors were used to confirm that the monitored anchors were stressed to the designed load of 195kN.
Each cell is connected to a wireless node that collects and relays data to a single gateway on-site. The gateway then sends the data to the GEO-Instruments monitoring software QuickView, where it is processed so it can be can be visualised by both contractors and clients.
QuickView is capable of live data processing, automated exceedance and outage alarms as well as automated distribution of scheduled site specific reports.
Each load cell location was also fitted with an additional thermistor to reliably and accurately measure changes in temperature. The data collected from these sensors will allow for comparison of load and temperature variations and identification of seasonal trends over short and long timescales.
“Working with the Keller team to provide a reliable, long term monitoring solution has been a great experience. I am really pleased with the performance of the load cells and am looking forward to using them more on future projects.” said Rob Orr, Project Manager at GEO-Instruments.
The cells will continue to collect hourly automated data for several years with no need for manual readings and minimal maintenance required for occasional battery swaps.
Elsewhere on the same site GEO-Instruments’ Site Engineering Team are also working alongside Keller providing Setting Out and Borehole Surveying services.
Find out more about our Team’s work on other retaining wall projects.
