Tunnelling Through: A Look at Impressive Underground Projects and How We’re Helping Them Breathe
Tunnels might not be the flashiest part of a city skyline or highway, but they’re often among the most awe-inspiring feats of engineering—hidden just beneath our feet. Whether slicing through mountains, dipping beneath oceans, or weaving beneath urban streets, tunnels shape the way we move and connect.
In this piece, we explore some of the most remarkable tunnels around the world, highlight the projects we’ve proudly contributed to, and take a closer look at one often-overlooked element that helps make these underground giants safe, quiet, and functional: ventilation.
Incredible Tunnels Around the World
Right now, one of the most exciting and record-breaking tunnelling projects is taking shape beneath the Baltic Sea: the Fehmarnbelt Fixed Link.
This colossal project, currently under construction, will connect Denmark and Germany via an 18-kilometre immersed tunnel, making it the longest of its kind in the world. Designed to accommodate both road and rail traffic, it’s set to dramatically reduce travel time between Copenhagen and Hamburg—offering a faster, greener alternative to ferry crossings or long overland routes.
What’s particularly fascinating about the Fehmarnbelt tunnel is how it’s being built. Giant concrete segments—each 217 metres long and weighing up to 73,000 tonnes—are being constructed in a dedicated tunnel factory on the Danish coast. Once complete, these massive pieces are floated into position and submerged into a specially dredged trench on the seabed. As of 2025, the first segments have been successfully placed, marking a significant milestone in this decade-long megaproject.
While the Fehmarnbelt Fixed Link is currently in the spotlight, it’s far from the only impressive tunnelling endeavour. Switzerland’s Gotthard Base Tunnel—the world’s longest railway tunnel at 57 kilometres—continues to push the boundaries of precision engineering. Norway’s Laerdal Tunnel, stretching 24.5 kilometres through mountainous terrain, is a standout for its innovative lighting and rest zones. And the Channel Tunnel, connecting the UK and France, remains one of the most iconic undersea tunnels after more than 25 years in operation.
Each of these projects tells a story of ingenuity, resilience, and complex system design. And behind all the concrete and steel, one vital piece keeps them functioning safely: ventilation.
Tunnels We’ve Helped Breathe Easy
At IAC Acoustics Australia, we’ve been proud to contribute to some of the most significant tunnel infrastructure projects in Australia and internationally. Our work focuses on tunnel ventilation attenuation systems that support both everyday operation and emergency readiness.
Key Projects Include:
1. WestConnex M4-M5 – Sydney, Australia
2. Sydney Metro (Martin Place, Barangaroo, Victoria Cross, and more) – Sydney, Australia
3. West Gate Tunnel Project – Melbourne, Australia
4. M6 Motorway Stage 1 – Sydney, Australia
5. MTRRC – Hong Kong
6. Orange Line Metro – Bangkok, Thailand
7. Delhi Metro – India
8. Caracas Metro – Venezuela
Case in Point: WestConnex M4 East
For this major Sydney infrastructure project, we delivered custom attenuators for the Parramatta Road and Underwood Road ventilation facilities.
Our design focused on reducing pressure loss while maintaining stable airflow during emergencies such as tunnel fires. Using Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA), we engineered solutions that met Australian safety standards, optimised long-term performance, and streamlined the installation process.
Tunnel Ventilation – A Hidden Hero
Underground infrastructure needs more than concrete and engineering precision — it needs air that moves safely and efficiently.
At IAC Acoustics Australia, we design and deliver ventilation attenuation systems that:
Reduce internal and external noise
Optimise airflow for both daily use and emergency conditions
Meet rigorous structural and acoustic standards
From airflow modelling to installation, our solutions ensure tunnels perform safely, quietly, and sustainably — from day one.
Want to Learn More?
If you’re working on a tunnel project and need expert support in ventilation attenuation or acoustic system design, we’d love to help.
Contact IAC Acoustics Australia to learn more about how we can support your next infrastructure development.