With twin nine-kilometre tunnels, five deep-level stations, advanced signalling and a high-capacity communications-based train control system, the Melbourne Metro tunnel is a $15 billion piece of infrastructure set to reshape how commuters move through the heart of the city. Four tunnel boring machines excavated simultaneously from both western and eastern portals. The machines operated at pressures up to three bar to maintain face stability through complex Coode Island Silt and Melbourne mudsto