Mary TBM: Herrenknecht megamachine on the River Torrens to Darlington project in Adelaide

Urban tunnel excavation demands cutting-edge technology to guarantee safety and technical accuracy. In Adelaide, the megamachine Mary is central to the River Torrens to Darlington (T2D) project, reshaping South Australia’s road network through highly advanced engineering.

How does the gigantic Mary tunnel boring machine work in Adelaide?

For the T2D scheme, a monumental unit built by Herrenknecht is being used to bore through local ground conditions. Measuring 100 metres in length, the system removes huge quantities of spoil as it steadily progresses beneath the suburbs of Clovelly Park and Glandore.

As it advances, it achieves around eight to ten metres a day of continuous underground excavation. Throughout the drive, the machine supports the tunnel walls and maintains ground stability, preventing any collapse during construction.

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Why does the tunnel boring operation run without interruptions?

Keeping the equipment running without stopping maximises productivity day and night in Australia. High-powered motors push the structure forward, while conveyor belts remove all the cut material, keeping the worksite highly efficient.

At the same time as the rock is being cut, the machine installs protective rings made from rigid concrete blocks. This synchronised automation stabilises the tunnel immediately, allowing the passage to be opened continuously with full operational stability for the technicians.

Below is a video from the Torrens to Darlington Project YouTube channel showing the operational details of this incredible piece of engineering:

What are the technical characteristics of this equipment?

This German tunnel boring machine weighs 3,500 tonnes and has a 15-metre-diameter cutting face. Its formidable scale makes it possible to create generously sized transport tunnels designed to handle high-flow vehicle traffic.

The TBM brings together integrated cutting systems, hydraulic support, and the placement of precast concrete elements. Each part is engineered to withstand the intense ground pressures involved in large-scale urban underground boring.

Specifications of the Mary Tunnel Boring Machine

Structural highlights - the key technical components of this underground excavation megamachine:

1. Circular cutting head with a 15-metre diameter for continuous boring;
2. Massive structure 100 metres long, weighing 3,500 tonnes;
3. Automated internal system for assembling concrete segments inside the tunnel.

How do specialists work inside the machine?

Up to 20 specialists can be working at the same time inside the structure during excavation. The team monitors electronic systems, manages boring progress, and carries out preventive maintenance on the cutting tools to keep the pace efficient.

Working internally requires rigorous safety training due to the conditions of the underground environment. Continuous ventilation and constant communication with the surface help protect the workers who accompany the megamachine throughout its daily continuous work.

Having professionals inside the tunnel boring machine covers several strategic roles that are vital to the project’s success:

• Real-time monitoring of the cutting head and ground pressure;
• Positioning and securing the concrete blocks used for lining;
• Daily mechanical inspection of the waste-transport components.

What is the importance of this project for infrastructure?

Building this road corridor improves urban circulation and reduces congestion across the region. Progress enabled by TBM technology minimises disruption to surface traffic and supports delivery within deadlines set by infrastructure management bodies.

Deploying this megamachine also sets new benchmarks for heavy engineering in major urban centres. The combination of mechanical power and specialist work demonstrates strong technical capability in delivering large-scale road projects across South Australia.