HARD ROCK EXCAVATION | EQUIPMENT


Above left: The AQ-6 drum cutter on CAT365 in tunnel Above right: Antraquip AQ-4 on a Chicago Transit Authority project


Despite the extreme conditions, the AQ 6 drum cutter delivered average production rates of ~12m3


per hour,


with higher outputs achieved under optimal conditions. The shaft and tunnel were completed on schedule, and the resulting profile was smooth and accurate, with minimal overbreak. This reduced the need for additional support and cleanup work, while low vibration levels allowed excavation to proceed without disruption to the city above. For the contractor and for Antraquip, this project


represented more than a normal successful outcome. It challenged long held assumptions about the capabilities of drum cutters in hard rock. Rock cutting at UCS levels exceeding 100MPa had


long been considered the territory of heavy roadheaders (100t or larger) or explosives, but the Montreal tunnel demonstrated that with the right equipment, setup, and operational approach, Antraquip drum cutters (roadheader attachments) can perform in these conditions. The project also underscored the importance of close collaboration between supplier and contractor. Engineering decisions made early in the process had a direct impact on production, efficiency, and tool longevity. As urban infrastructure projects become more


complex and restrictions on disruptive excavation methods increase, solutions like this are becoming more valuable. Advanced rock cutting technology offers a cleaner, safer, and often faster alternative, especially in sensitive environments. This Montreal metro ventilation tunnel project stands as a case study in pushing the boundaries of what is possible in underground construction.


IMPACT ON FUTURE PROJECTS The success of the Montreal ventilation tunnel has influenced how contractors and engineers approach excavation in extreme hard rock. By demonstrating that a high powered drum cutter could maintain steady production in UCS ranges traditionally reserved for drill and blast, the project expanded the possibilities for advanced rock cutting methods in sensitive, high density urban environments.


A key part of that success was the AQ 6’s engineering.


Its robust transmission, reinforced drums, strategically designed pick configuration, and dedicated hydraulic power unit created a combination capable of sustained operation in some of the toughest ground conditions. This performance has set a new benchmark for what can be achieved when a cutter combines power with a design tailored to its geology. Contractors who once deemed this type of work impossible without blasting now see advanced drum cutters as a practical and, in many cases, preferred solution. Since Montreal, similar strategies have been used


on projects where precision and vibration control were critical. In Chicago, the Transit Authority needed to remove


a 100 year old concrete embankment wall directly adjacent to existing buildings and infrastructure. The wall ranged from 18 inches to six feet thick, with some sections just inches from nearby structures. Seismic monitoring stations were installed to protect the surrounding infrastructure. Conventional demolition tools, like pneumatic hammers, were ruled out due to excessive vibration. The solution chosen was to use an Antraquip AQ 4 hydraulic drum cutter, which delivered controlled grinding of the thick concrete into manageable debris while keeping vibration well within seismic limits. The project was completed safely, efficiently, and without damage to nearby structures, proving the value of precision cutting in sensitive urban environments. This type of application reinforces the importance of


early collaboration between equipment suppliers and project teams to fine tune machine configuration, tool selection, and operating parameters. As infrastructure projects face greater scrutiny for environmental impact and safety, the strategies proven in Montreal and successfully applied in projects like Chicago offer a reliable model for delivering on schedule and within budget while minimising disruption. The outcome shows that with the right technology and expertise, even the most challenging ground conditions can be tackled efficiently to create safer and more sustainable underground construction.


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