The Gotthard Base Tunnel in Switzerland stretches a mind-boggling 57 kilometers beneath the Swiss Alps. At its deepest point, nearly 2. 5 kilometers of solid granite sit above the tracks, creating intense geothermal temperatures and massive pressure challenges.
To ensure passenger safety, engineers designed two emergency multifunction stations—most notably at Sedrun—featuring vertical ventilation shafts dropping 800 meters straight down into the earth. The air balance physics governing these deep shafts are a marvel of fluid dynamics. High-speed trains blasting through the twin tubes at 250 km/h act like giant pistons, pushing massive waves of compressed air known as the piston effect.
Without precise ventilation management, these shockwaves could destroy emergency doors or fill escape routes with smoke during a fire. To counter this, massive surface fans and adjustable dampers dynamically balance the pressure differential between the main tubes, emergency stations, and vertical shafts. During an emergency, the system shifts into hyperdrive.
Powerful fans force fresh air down the 800-meter shaft to overpressurize the emergency evacuation halls. This creates a positive pressure barrier that physically prevents toxic smoke from leaking into safe areas, even if doors are opened. Simultaneously, exhaust systems use the natural stack effect—the buoyancy of warm air rising through the giant vertical chimney—to suck smoke out of the rail tubes.
Balancing these thermodynamic forces requires constantly adjusting for outdoor weather, indoor geothermal heat, and transient pressure spikes caused by passing trains.