Intelligent monitoring solution ensures highway safety amid high-speed rail construction

Author: Megan Hanssen is Product Marketing Manager at Leica Geosystems, part of Hexagon, Simon Hall is Content & Distribution Marketing Executive at Leica Geosystems, part of Hexagon, Craig-Lee Holt is Monitoring & Tunnelling Solution Specialist at Leica Geosystems, part of Hexagon

As critical transportation projects take place across the United Kingdom, monitoring existing nearby infrastructure for deformations is essential to ensure safety and continued operation. During the tunnelling of the HS2 high-speed railway under the M25 highway near London, SOCOTEC UK — a provider of testing, inspection and certification services — successfully monitored the difficult-to-access, busy motorway. SOCOTEC used a solution from Leica Geosystems, featuring automated laser scanning and a range of other monitoring techniques.

A high-speed train, a critical highway and a monitoring challenge

Great Britain’s first passenger railway opened in 1830, initiating a transit revolution. Nearly two centuries later, U.K. commuters still ride railways laid in the Victorian era. However, demand for more lines and faster cross-country connections has outpaced rail infrastructure development. The U.K.’s High Speed 2 (HS2), a high-speed railway currently under construction, will help alleviate these problems by linking major cities and airports to further connect Great Britain’s largest economic regions.

Building this extensive railway between major cities, including London, Birmingham and Manchester, requires tunnel construction that could disrupt existing transit and create structural deformations to the roadways above. Tunnelling under the M25 posed such a risk. This critical national highway carries more than 250,000 vehicles each day along approximately 188 kilometres of tarmac. The construction of two separate tunnels underneath this asset, in particular, led National Highways — a government-owned company in charge of maintaining the M25 — to require a monitoring solution that would ensure the safety of travellers and evaluate the structural integrity of the roadway throughout the project.

Monitoring such a busy highway, however, posed problems: The roadway, with consistently high traffic volumes, had only limited access to monitoring areas and it was not feasible to close the highway for the initial or regular data collection during construction periods. At the same time, it was impractical to install prisms on the road surface where they would be destroyed by heavy vehicles or traffic would have to be redirected to avoid them.

Industry leader SOCOTEC UK takes on the challenge

To meet this challenge, Align — the joint venture company completing 21.6km of the rail infrastructure, including the 16.04km twin-bored tunnels under the M25 — contracted monitoring experts from SOCOTEC UK. This provider of testing, inspection and certification services across industries specialises in geotechnical and structural monitoring and has more than 30 years of experience on large-scale civil engineering projects like the Victoria Station Upgrade in London.

SOCOTEC UK not only considered the practicality of the setup in terms of access and instrument installation, but they also wanted to minimise disruptions and, most importantly, secure the safety of M25 travellers and their own staff while working along the highway. Therefore, they required a solution with minimal installation to the road surface, reduced installations to earthworks and the ability for the monitoring system to be fully remote and run autonomously 24/7 over several years.

Dedicated to digital innovation, SOCOTEC UK saw this as an opportunity to incorporate laser scanning and automation available through monitoring solutions from Leica Geosystems.

Patch scanning: a nonintrusive monitoring solution from Leica Geosystems

The custom monitoring setup was designed in consultation with SCCS, part of Hexagon, and the U.K.’s leading Leica Geosystems distributor, and incorporated a range of automated features, including patch scanning, imaging, instrument levelling and reporting.

“We chose SCCS to provide us with the hardware, software and the customer support we needed to install a system capable of surveying accurate patch scans, prisms and reflectorless points,” explains Jeff Foggo, Senior Project Manager at SOCOTEC UK.

To solve the access and disruption issues, SOCOTEC UK chose a unique, non-intrusive monitoring solution called patch scanning that utilises laser scanning and automated monitoring software to generate data and analyses. The combination of the  MS60’s highaccuracy laser scanner, capturing thousands of points per second, with GeoMoS software minimised the need to install reflective targets or prisms and enabled monitoring to proceed in even the most restrictive areas. This decreased disruptions to live traffic during installation and operation, removed SOCOTEC UK staff from potentially hazardous areas and ensured safety for road users.

SOCOTEC UK captured reference measurement data for 12 months ahead of the excavations to determine the normal movements of the road surface. During the monitoring period, the MS60, installed high up on adjacent plinths to optimise visibility, scanned small areas or “patches” of surfaces at determined intervals with arrays of 20, 40 and 60 metres. Other measurement arrays included prisms set up on the top of the embankments and multiple reflectorless points on structures. Additional prisms were installed as survey control in stable areas.

Utilising hybrid techniques with MultiStations helped SOCOTEC UK optimise their monitoring installation and ensured impeccable measurement reliability. GeoMoS compared the measurements to baseline reference values, enabling deformation detection and notifications to key stakeholders if tolerance thresholds for movements were exceeded.

Additional automation for 24/7 monitoring

Complementing the patch scans, SCCS also recommended further automation of the project using imagery to minimise visits to the site. Remote access to live video and still images via integrated cameras in the  MS60 made it possible to easily resolve and verify any data measurement questions without delay.

The intelligent measurement sensors, including the  MS60s and TM50, were centrally controlled through GeoMoS and used custom power sources with backups to ensure continuous monitoring. Additionally, since the instruments were installed in remote locations where environmental factors could impact stability, SOCOTEC UK needed a way to ensure the total stations remained level. Connected through the ComGate20, GeoMoS remotely and automatically activated the AD12 selflevelling tribrach for each TPS before each measurement cycle, ensuring result quality and reducing maintenance visits.

However, SCCS provided more than the instruments and software — they also supported SOCOTEC UK with remote and on-site training during the operation and delivery of the monitoring scheme and overall solution.

Continuous monitoring benefits from constant protection

To protect the valuable equipment in the field, SOCOTEC UK mounted the instruments within secure cages and installed the Leica LOC8 theft deterrence and location solution. LOC8 enables geofencing, custom alerts via messaging and instrument tracking and locking. When three instruments were stolen from the site, SOCOTEC UK was able to provide tracking information to local police, who recovered 120,000 British pounds (roughly 138,000 euros) worth of stolen equipment. Once returned, the instruments were inspected, serviced and quality checked by SCCS before returning to the site so monitoring could resume as quickly as possible.

Results of the innovative monitoring system

SOCOTEC UK’s use of the Leica Geosystems monitoring solution allowed the M25 to operate as usual during the tunnelling period, ensuring that one project to improve transportation did not interfere with critical existing transit.

“Through our collective effort with SCCS, we confidently monitored the M25 and surrounding assets on an hourly basis during the passing of two tunnel boring machines under the M25 along the HS2 in quick succession,” reflects Foggo.

“Having the opportunity to provide an innovative monitoring system for one of the busiest parts of the highway infrastructure in the U.K. has been, and continues to be, a rewarding experience. The data certainly spoke for itself in terms of the monitoring system being a success: The record of minimal asset movement was clear during the tunnelling phase and all stakeholders, such as National Highways, received the reassurance they required.”

Monitoring experts leveraged an automated monitoring system to enable a major highway in the United Kingdom to remain open during extensive rail construction underneath it. To keep commuters safe and roadways operational, deformation data was autonomously and continuously collected with a laser scanning total station and automatically analysed in monitoring software, complete with automated reporting and notifications to stakeholders.