the morning of our visit, we arrived at the Sydney Metro West project site at 10 AM, traveling from our hostel to the location near Rosehill Gardens Racecourse. The presenter of the presentation was Hau Wei Ng, who is the Deputy Project Director. Our excursion included a presentation from Gamuda, the main contractor, along with insights from Mott MacDonald, a consulting firm involved in the project. This report summarizes key points discussed during the visit.
The Sydney Metro is Australia’s largest public transport project, aiming to develop a network of 46 stations and 113 kilometers of rail by 2030, with construction starting in 2020 and completion expected by 2032. The project is overseen by Sydney Metro, a government body responsible for its development and expansion. The Sydney Metro project exists of three packages: Eastern Tunneling Package, Western Tunneling Package and Central Tunneling Package. This excursion includes the Western Tunneling Package, existing of 9 km of twin metro rail tunnels between Westmead and Sydney Olympic Park.
Gamuda serves as the primary contractor for this ambitious initiative. A crucial aspect of construction is the Tunnel Boring Machine (TBM), which is designed for efficient and safe tunnel excavation. The process begins with creating a “station box” using sheet piles to facilitate TBM entry and station construction. Additional excavation occurs further from the station site to optimize space. Gamuda is at the forefront of innovation in tunnel construction with its introduction of autonomous tunnel boring machines (A-TBMs), named Betty and Dorothy. These groundbreaking machines are capable of navigating through underground tunnels with minimal human supervision, thanks to their advanced sensors, control systems, and artificial intelligence. This technology allows the A-TBMs to make real-time adjustments to their operations, ensuring precise alignment with the tunnel design limits and optimizing excavation processes.
The A-TBMs excel in various automated functions. They can adjust their speed and rate of excavation based on real-time ground conditions and excavation permits, ensuring that operations are conducted safely and efficiently. Additionally, they automatically regulate the speed of screw conveyors, which transfer excavated material, maintaining optimal crown pressure throughout the process. The machines also balance slurry levels in the working chamber by adjusting the speeds of multiple slurry pumps, further enhancing operational efficiency and safety
Automation plays a significant role in addressing the shortage of trained operators. The TBM is equipped with automated systems for steering, advancing, and excavation, enhancing operational efficiency. The use of automation has resulted in an average time reduction of 8.41% when operating in auto mode, although further research is ongoing to understand the reasons behind this improvement.
The TBM can theoretically excavate up to 108 meters in a 24-hour shift, though maintenance and unexpected issues often reduce this output. Each tunnel segment comprises eight uniquely shaped precast concrete parts designed for curves. A water management system ensures sufficient operational supply, with a treatment plant processing 50 liters per second. Approximately 40-45% of treated water is reused within the project, while the remainder is discharged after treatment. Excavated dirt is either reused or exported, emphasizing material recycling.
Currently, two TBMs are operational but still in the startup phase. A crane is being used for dirt transport until the conveyor belt system becomes operational. The segments are secured with bolts, and their thickness varies to accommodate tunnel direction changes. While tunneling can cause vibrations that affect nearby structures, the rate of 200 to 250 meters per week helps minimize disruptions.
Furthermore, sustainability and innovation are standout features of the project. A precast area is established for producing concrete components, utilizing the highest cement replacement rate ever seen in Australia, contributing to more sustainable construction practices.
During our visit, we were able to pose several questions about the project and its operations. We learned that explosives are not used for excavation due to the soft ground materials, although they may be necessary in other projects with harder soil. Both Malaysian and Sydney clients supported the automated TBM (ATBM) technology, facilitating its implementation. While steering and operation are automated, other functions remain manual, with hopes for further automation in the future. The project team clarified they do not plan to sell their proprietary software for the ATBM to maintain a competitive edge.
The visit to the Sydney Metro West project provided valuable insights into a significant public transport initiative. The emphasis on automation, sustainability, and innovative techniques reflects a forward-thinking approach to urban infrastructure development. As the project advances, it promises to enhance Sydney’s public transport capabilities and set a benchmark for future tunneling projects.