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Metrolinx projects utilize cutting edge tech and techniques in the digging and boring sectors

Metrolinx, a Crown corporation owned by the Government of Ontario, manages road and public transportation in the Greater Toronto and Hamilton Area. The corporation have many projects underway, including ongoing extensions to its Ontario Line, the Eglinton Crosstown West Extension and the Scarborough Subway Extension projects. Each of these projects involve a variety of new technologies and techniques in the digging and boring sectors.

New Technologies at Play
“Tunnel boring machines (TBMs) have been used on a number of Metrolinx projects,” says Andrea Ernesaks, Metrolinx’s senior manager of media relations, when asked how the digging sector has evolved in recent years. “Modern TBMs have been around since the 1960s, however there have been major advancements in technologies used in TBMs in recent years.”

Those advancements include navigational systems, ground treatment and face stabilization techniques, as well as better cutting tools and more accurate and real-time visualization of data. These advancements have enabled faster excavation rates and tunnel liner installation which has reduced the time it takes to complete a tunnel.

“There has also been a shift towards more sophisticated tunneling methods using TBMs,” says Ernesaks. “In the last decade or so, the Earth Pressure Balance Machines (EPBM) and slurry shield TBMs have been introduced, with both machines able to excavate in various ground conditions effectively.”

For the uninitiated, EPBMs are shield TBMs designed for use in soft ground conditions. The key feature is that they use the excavated soil as a support medium and achieve a balance with the pressure in front of the cutterhead. Slurry shields are TBMs fitted with a cutterhead that covers the entire face of the device, providing support through pressurizing boring fluid inside the chamber.

Ernesaks also notes that there is a heightened focus on safety measures and environmental sustainability, especially in urban areas. Improved ventilation systems, advanced monitoring technologies for ground settlement and tunnel integrity, and stricter adherence to environmental regulations have become standard practices.

Integrating the tech
Regarding how these advances have been incorporated into Metrolinx’s projects, Ernesaks says that their TBM guiding system is becoming more sophisticated with each project. Their surface monitoring system went from manual to a fully automatic digital system for one example. Metrolinx also uses better ways of transporting segments into the tunnel and supplies to the TBM through wheeled transport. Tunnel belts are used to remove material, rather than muck boxes on a train and rail track.

“Remote controlled robots were also used in the tight underground tunnels for the Eglinton Crosstown West Extension. These mini excavators crawled around on Caterpillar tracks and were used to dig a cross passage between the two parallel tunnels.”

In the Scarborough Subway Extension, increased use of wear detection tools allows TBM operators to better understand the condition of the front cutterhead. Beyond wear detection, there are also continued improvements to the capabilities of TBMs to respond to changing geotechnical conditions through advanced ground conditioning agents which are injected to allow for better muck control.

“New technologies that have advanced and evolved over time have also been used in this project. This includes ground deformations monitoring using Shape Accel Arrays combined with Automated Motorized Total Stations at critical infrastructure crossings.”

Metrolinx also employs Geotechnical Monitoring Systems to keep on top of ground conditions during tunnelling and construction activities. That way, potential issues such as ground settlement or instability can be detected more quickly and mitigated.

The Benefits of New Tech
The primary benefit of employing these new technologies is improved safety for both workers and the public. Advanced monitoring systems and automated processes minimize risk and work in concert with enhanced safety protocols and training programs.

“These techniques also increase construction and operational efficiencies. For instance, advanced TBMs and robotics speed up excavation and construction processes,” says Ernesaks. “Prefabrication and modular construction techniques reduce on-site work time and improve project scheduling. Data analytics also optimize resource allocation and enhance project management.”

While some may be turned off by the initial investment costs in these technologies Ernesaks notes that they often lead to cost savings in the long term. These investments can lead to faster construction timelines which reduce labour costs and overhead expenses. Energy-efficient systems also lower operational costs and predictive maintenance and smart infrastructure will reduce lifecycle maintenance costs.

“In addition, innovations such as trenchless technology and modular construction techniques minimize disruption to urban environments. This includes reduced noise, traffic congestion, and surface disturbance during construction. Better logistics planning and community engagement strategies further mitigate disruptions.”

However, there is often a growing period when new technologies are introduced. Sometimes, the initial offerings into a sector take time to fully mature – i.e. for the most optimal usage of that technology to be hit upon. Ernesaks says that full maturity is achieved when new tech is widely accepted and integrated into standard practices across the industry.

“This stage typically involved widespread adaptation, proven reliability in diverse project environments, and demonstrated benefits in terms of safety, efficiency, cost-effectiveness, and sustainability,” says Ernesaks. “As more complex projects are completed, there are more improvements/lessons learned which are incorporated into future designs of TBMs.”

To the Future
Asked about what the next frontier of technologies for the tunnelling and digging sectors will be, Ernesaks says that Metrolinx and other sector experts have discussed several possible future developments.

While TBMs are at the current cutting edge, autonomous TBMs are currently being researched. This equipment would allow for minimal human intervention, which would enhance safety and efficiency. These technologies could also potentially lead to continuous 24/7 operations.

“Robotics and artificial intelligence are expected to play a larger role in construction activities,” says Ernesaks. “Robots could assist in tasks such as reinforcement installation, concrete spraying, and even maintenance activities post-construction. Integration of data analytics and artificial intelligence would also allow TBMs to analyze geological data and numerous sensors more effectively.”

Finally, Ernesaks points to the development of advanced materials and construction techniques as another new frontier. Innovations in materials science could lead to stronger and more durable tunnel linings which would reduce maintenance needs and extend the lifespan of infrastructure.

“Prefabrication techniques for tunnel segments and station components may become more advanced, speeding up construction timelines,” adds Ernesaks.

Tunnelling and construction is already underway for the Ontario Line, the Eglinton Crosstown West Extension and the Scarborough Subway Extension.