Protecting Key Infrastructure During Tunnelling

Case Study

Protecting key infrastructure during tunnelling

Authors: Simon Hall & Roger Dixon

In today’s modern and growing world of business logistics, construction companies are on a journey. A journey to create a new, better, brighter, and inspiring environment for industrial & logistics business.

The SEGRO Logistics Park Northampton (SLPN) is strategically located adjacent to the M1. The new site will occupy over 5 million square feet of land, with design and build units available up to 1.3 million square feet. The new logistics hub will include 7 new distribution plots, and a new strategic rail freight interchange onsite.

A key part of the construction of the new logistics hub was the boring of a 1200mm diameter service tunnel, 14 metres below the surface of Junction 15 of the adjacent M1 motorway. This presented a signification challenge to the construction team, as any movement from to the carriageway above posed a significant risk of damage, as well as increasing the potential for accidents and risk to human life.

The M1 motorway is one of the UK's busiest motorways running from London in the South to Leeds in the north of England. It has been the first inter-urban motorway to be completed in the UK. The motorway is 193 miles (311 km) long and was constructed in four phases. Most of the motorway was opened between 1959 and 1968. The southern end was extended in 1977 and the northern end was extended in 1999.

SEGRO contracted the Graph Survey Partnership (GSP) to conduct monitoring activity on the motorway during tunnelling. GSP is a highly specialist engineering surveying company, providing services to clients of all sizes across the UK. This may range from a survey on a small parcel of land, to a major motorway construction project for a blue-chip company. The company was formed by four founding directors, who had each ran their own successful individual practices, with their combined skills to fill the growing need to undertake larger and more complex contracts.

 

Protecting key infrastructure during tunnelling

The carriageway of the M1, which ran 14m above the new maintenance tunnel.

 

The ability to remotely monitor the M1 during tunnelling operations was not possible by conventional means. This was due to the length of the crossing, combined with a lack of height when using a tripod at ground level. There were also various crash barrier obstacles in place through existing construction works.

There were also large quantities of information that required filtering. Once a day, this data, in CSV format, was provided with results from the previous 24 hours. This would enable Geotechnical Designers to advise National Highways on to whether the next day’s operations could continue.

GSP needed a 24 hour a day, 7 days a week monitoring system that would measure deformation of the carriageway during tunnelling operations keeping the motorway open and safe. National Highways would not permit tunnelling operations to begin without a monitoring solution being in place.

“I first heard about Leica GeoMoS Monitor at GeoBusiness 2021 and watching a presentation by Craig Holt. Graph already owned a Leica Nova MS50 and had previously used it for an Arch culvert construction and loading the embankment above.”
Roger Dixon – Director | Graph Survey Partnership

The Leica Nova MS60, the world’s first self learning MultiStation, enabled GSP to perform all the required monitoring tasks with a single instrument, bringing sensor fusion to the next level by combining highest-end total station capabilities, laser scanning and digital imaging. Highly accurate angle and distance measurements, long-lasting design are key elements of modern total stations, fully embodied in the MS60. With improved automation functionalities, the MS60 increased efficiency, even under the challenging conditions posed by monitoring a live dual-carriageway motorway. To ensure the total station always remained level, the AD12 Self Levelling Tribrach was used for automatic self-levelling.

 

Protecting key infrastructure during tunnelling

The Leica Nova MS60 mounted during the monitoring project.

 

To support the connection to the monitoring sensor, GSP chose Leica GeoMoS Monitor. The software  allowed GSP a seamless connection, sensor control and instant data storage and analysis. The GeoMoS software suite allowed for the set up and automatic daily generation of the required reports, ensuring a round-the-clock measurement cycle with sensor scheduling. If the system status and the limit check of critical observations was activated, GSP and other responsible individuals were informed.

Every automated monitoring project requires not just sensors and software, but also power and communication components in the field. Designed with simplicity in mind, the Leica ComGate20 was integrated in the field cabinet and connected to the MS60. The configuration of the MS60 is then performed off site in one centralised view within the Leica GeoMoS monitoring project. This significantly sped up the configuration process and gave GSP full control over the measurement settings and scheduling.

“The entire solution was implemented after the Project Managers and Asset Owners were consulted during planning meetings 12 months prior to the commencement of the tunnelling operation. A meeting and presentation by Craig Holt to WINVIC’s Civils Design Manager was set up to initially explain the advantage of patch scanning over single reflectorless readings.”
Roger Dixon – Director | Graph Survey Partnership

The solution implemented, with support from Leica Geosystems and SCCS, provided patch scanning and prism monitoring data, gathered using the MS60 mounted on a newly installed motorway gantry.

The system operated continuously relying on a bespoke solar panels and battery solution designed and implemented by Leica Geosystems and SCCS part of Hexagon for the project. No power outages or battery changes have been required for the whole duration of the project (over 3 months).

 

Protecting key infrastructure during tunnelling

Security boxes in place to protect the Communications and Power Solutions from SCCS

 

Using the combined solution, GSP used patch scanning to take an average of 10,000 readings to compare against, rather than a single reflectorless reading which could be on a stone or on the tarmac texture. This saved a 3-engineer team on a rota taking single reflectorless readings on to the carriageway from both sides of the road over a 14 week period.

The monitoring solution not only provided safety for the motorway during tunnelling operations but also delivered the most safe methodology to perform and manage the measurements, with full remote control and no need for any operation on site.

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