C+S March 2023 Vol. 9 Issue 3 (web)

Critical and large-scale transportation projects have become a com- mon feature of the UK’s landscape in the last fifteen years, includ - ing, most recently, Crossrail, a hybrid commuter rail and rapid transit system crossing the capital, and HS2, a high speed rail service which will connect London to the West Midlands. Central to the safety and uninterrupted operation of these projects is the monitoring of existing nearby infrastructure for deformations. During the tunneling of the HS2 railway under the M25 highway near London, SOCOTEC UK successfully monitored the difficult-to-access and busy motorway with a Leica Geosystems solution featuring automated laser scanning and a range of other monitoring techniques. A high-speed train, a critical highway and a monitoring challenge Britain’s first passenger railway opened in 1830, initiating a transit rev - olution. Nearly two centuries later, UK commuters still ride railways laid in the Victorian era while demand for more lines and faster cross- country connections has outpaced rail infrastructure development. The UK’s High Speed 2 (HS2), a dedicated high-speed railway currently under construction, will help alleviate these problems by linking major cities and airports to further connect Britain’s largest economic regions. However, building this extensive railway between major cities, includ - ing London, Birmingham, and Manchester, requires tunnel construc - tion that potentially could disrupt existing transit and create structural deformations to the roadways above. This was the case for tunneling under the M25, a critical national highway carrying over 250,000 ve - hicles each day along 117 miles of tarmac. Particularly, the construction of two separate tunnels underneath this asset 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’s progression. Monitoring such a busy highway, however, posed problems: the road - way, 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 complet - ing 21.6 kilometers of the rail infrastructure, including the 16.04 km twin-bored tunnels under the M25 – contracted monitoring experts Going Underground: The UK’s busiest highway meets its fastest railway network

from SOCOTEC UK, a leading UK provider of testing, inspection, and compliance services across industries. With specialisations in geotech - nical and structural monitoring and over thirty years of experience on large-scale civil engineering projects like the Victoria Station upgrade in London, they were the perfect project partner. SOCOTEC UK not only considered the practicality of the setup in terms of access and instrument installation, but they also wanted to minimize 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 oppor - tunity to incorporate laser scanning and automation available through the Leica Geosystems monitoring solution. Patch scanning: A non-intrusive monitoring solution from Leica Geosystems The custom monitoring scheme was designed in consultation with SCCS, part of Hexagon and the UK's leading Leica Geosystems dis - tributor, and implemented a range of automated features, including patch scanning, imaging, instrument leveling, 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 Leica Nova MS60’s high- accuracy laser scanner, capturing thousands of points per second, with GeoMoS software, minimized 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 twelve months ahead of the excavations to determine the normal movements of the road surface. During the monitoring period, the MS60, installed


March 2023 csengineermag.com

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