Building a huge infrastructure project like the West Gate Tunnel is no simple task. And excavating 6.8km worth of tunnels means calling upon a team of experts to work in unique underground conditions.
Key to digging the project’s twin tunnels are two gigantic tunnel boring machines (TBMs). These 15.6-metre-high machines will dig through the ground under Yarraville at a rate of around nine metres per day, taking over 18 months to complete the tunnel digging.
But how exactly do you operate these 4,000 tonne, 90-metre long machines?
Not just anyone can jump in and start working – in addition to highly specialised skills, TBM workers need to manage the pressurised environment they will be working in, often for extended periods of time.
When operating the TBM, workers will be around 15 to 35 metres below sea level, meaning there will be significant changes to conditions they are used to surface. The increase in air pressure can be likened to that of scuba diving to a depth of 35 metres for several hours.
Before training for these conditions can begin, workers undergo rigorous medical examinations to make sure they are fit for the job. Once these are passed, training starts in a hyperbaric (compressed air) environment, replicating the conditions of working below the surface.
The West Gate Tunnel Project’s hyperbaric chamber is located at the project’s northern portal construction site in Footscray. The small chamber houses two beds, a phone, a viewing area for the lock operator, pressure gauges and a portal for receiving food and medical supplies.
Workers will spend time here to acclimatise to the changed conditions and gain a full understanding of what life will be like tunnelling below the inner west.
Meanwhile, a ‘training tunnel’ has been built at Victoria University’s Werribee East campus to help future tunnellers familiarise themselves with working in a tunnel and where services such as compressed air are located and other key components such as the spoil conveyor which will take rock and soil from underground up to a shed, before it is trucked away.
Last year, Victoria University Polytechnic reopened its Werribee East campus as a Technology Precinct centre on Civic Construction to accommodate the additional training needs of the West Gate Tunnel Project.
The West Gate Tunnel Project tunnelling operations will take place 24 hours a day, seven days a week, with up to 20 people working on the TBMs at any one time.
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Photo caption: Hyperbaric consultant Geoff helps prepare the West Gate Tunnel Project team with some compressed air training.