Tunneling, a vital part of infrastructure development, encounters increasing challenges due to the rising complexity of construction. As urbanisation expands and infrastructure demands grow, conventional tunneling methods often prove insufficient. There is an imperative need for innovation in tunnel construction to overcome geological obstacles, minimize environmental impact, and enhance overall efficiency. Emerging technologies offer promising avenues to address these complexities. These innovations not only streamline construction processes but also contribute to creating safer, more sustainable, and resilient underground infrastructure.
In this context, Snowy Hydro Ltd is extending the legacy established decades ago by the original Snowy Mountains Hydro-electric Scheme. They are accomplishing this by applying innovative solutions to one of the most challenging engineering endeavours globally
About the project
The Snowy 2.0 project, led by Italian infrastructure group Webuild in collaboration with Snowy Hydro Ltd, stands as a remarkable extension of the original Snowy Mountains Hydro-electric Scheme. Positioned as the largest committed renewable energy venture in Australia, it significantly contributes to the government’s ambitious aim of achieving net-zero emissions by 2050.
Once completed, Snowy 2.0 will increase by 2200 MW the generating capacity of the existing scheme of 4100 MW. It will have 350,000 MWh of large-scale storage for the grid —enough energy storage to power three million homes for a week.
Work being executed
Webuild is currently excavating over 40 km of tunnels to link the upper Tantangara Reservoir with the lower Talbingo Reservoir. Within this network, a cavern of 485,000 m³ is being carved out to accommodate a power station situated 700 meters underground. The operational process involves releasing water from the upper reservoir, which flows through the tunnel to the power station. There, six Francis pump-turbines generate electricity before the water is discharged into the lower reservoir. To enhance efficiency, excess renewable energy is used to pump the water back up to the upper reservoir during periods of low energy demand. This closed-loop system ensures that Snowy 2.0 delivers flexible, on-demand power.
Webuild has achieved an industry milestone with its Force Activated Coupling System (FACS), a groundbreaking technology strengthening the walls of the Inclined Pressure Shaft (IPS) through which the water passes. This innovation, akin to the pioneering spirit of the original Snowy Hydro, builds on past successes such as rockbolting, which significantly improved tunnel and cavern lining support techniques to prevent rock collapses during excavation.
Force Activated Coupling System (FACS):
The Force Activated Coupling System (FACS) is an innovative technology introduced by Webuild in the Snowy 2.0 project, transforming tunnel construction and reinforcement, particularly in the Inclined Pressure Shaft (IPS). FACS’s groundbreaking features contribute significantly to the project’s success and the broader landscape of sustainable energy solutions.
What is FACS?
A force-activated coupling system for precast concrete segments is a method of connecting individual precast concrete elements to form a larger structure. This system relies on the application of forces, such as compression or tension, to establish a secure connection between adjacent segments. By utilizing force, these coupling systems ensure a strong and reliable bond, contributing to the overall stability and integrity of the precast concrete structure.
Primary Lining Procedure
Traditionally, the construction involves the installation of primary lining, consisting of pre-cast concrete segments arranged in rings. This process is executed within the tunnel excavated by a tunnel-boring machine (TBM). The primary lining may be composed of steel or cast in-situ concrete with a reinforcing steel cage.
FACS Advantages
By obviating the need for the secondary lining, the FACS contributes to expedited tunnel completion. Additionally, this innovative technology facilitates an enlargement of the tunnel’s inner diameter, allowing for a greater volume of water flow.
FACS Components and Installation
The FACS comprises two key components – a male and a female pin-socket steel coupler. These are strategically installed on the longitudinal sides of pre-cast concrete segments produced at the factory in Cooma.
Installation Process
During tunnel excavation by the TBM, the segments equipped with FACS are integrated seamlessly, akin to conventional segments. As they are positioned, the male coupler of one segment seamlessly slides into the female socket of the next. This interlocking mechanism results in the compression of the coupler’s interior.
Functional Benefits
This compression mechanism enhances tensile resistance within the segments, mitigating the risk of misalignment and dislocation under the substantial internal transient pressure experienced within the waterway.
Inclined Pressure Shaft (IPS) for the project
The Inclined Pressure Shaft (IPS) is an engineering marvel within the Snowy 2.0 project, playing a pivotal role in hydroelectric power generation. Its colossal dimensions and operational capabilities set it apart, making it a benchmark on a global scale.
The IPS boasts a diameter of 10 meters, a length of 1.6 km, and a 25-degree incline, showcasing remarkable engineering ingenuity. This ambitious design facilitates the efficient return of water to the upper reservoir during periods of surplus renewable energy production and low energy demand, contributing to the overall efficiency of the hydropower system.
Operational Challenges
Operating at the forefront of hydroelectric power generation, the IPS faces extreme pressures and forces, especially during turbine shutdowns. The abrupt stop in water flow generates transient pressure surges and high-pressure waves, making structural fatigue a critical consideration over the project’s expected 150-year lifetime. The IPS’s ability to withstand these operational challenges underscores its robust engineering.
Global Significance
As the largest inclined pressure shaft globally, the IPS in Snowy 2.0 not only contributes significantly to Australia’s renewable energy goals but also establishes a benchmark on a global scale. Its design and capabilities mark a milestone in hydropower engineering, showcasing the industry’s ability to tackle complex challenges and push the boundaries of what is achievable.
Engineering Expertise and Commitment to Innovation
Webuild, Italy’s preeminent infrastructure group with 85,000 employees worldwide, spearheads the IPS project. Renowned for hydropower projects and global infrastructure initiatives, Webuild’s expertise is showcased in significant Australian projects such as Melbourne’s City Loop, North East Link, Sydney Metro Northwest’s skytrain viaduct and cable-stayed bridge, and Perth’s Airport Line.
Conclusion
The synergistic integration of the Force Activated Coupling System (FACS) and the Inclined Pressure Shaft (IPS) in Snowy 2.0 represents a leap forward in tunnel construction and hydropower generation, with far-reaching implications for the future of sustainable energy.
References- createdigital.org.au, smec.com
