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📘 The shortest route goes through the rock

Stand at Erstfeld in northern Switzerland and imagine the old railway climbing toward the Gotthard Pass.

5
lessons
~25 min
to learn
Adults
level
Start the course →

What you’ll learn

  1. A railway under the mountainExplain why Switzerland built a low-gradient, two-tube railway through the Alps and why the main tubes are only part of the underground system.The Base Tunnel replaces a steep mountain crossing with a 57-kilometre route surrounded by access, safety, and service infrastructure.
  2. Meet the gripper machinesDescribe how a hard-rock gripper TBM cuts, braces, advances, and supports a tunnel while carrying a factory's worth of equipment behind its cutter head.The Gotthard machines were long, heavy industrial systems whose cutting faces depended on bracing, spoil removal, maintenance, and logistics.
  3. Four machines, several directionsDistinguish Sissi, Heidi, Gabi I, and Gabi II and connect their names to the project's parallel work sections and breakthroughs.Four Herrenknecht gripper TBMs attacked different sections from north and south, turning one vast project into coordinated drives.
  4. What the rock gives backFollow the material and structural consequences of excavation from spoil removal and immediate support to the permanent railway system.A tunnel becomes usable through layers of handling, support, lining, track, power, signalling, safety, and testing after the cutter head moves on.
  5. The machine disappears into the resultReframe the TBM as one component in a multi-decade infrastructure system and reflect on why the machine's output becomes invisible to passengers.The cutter head vanishes into a stable route whose ordinary use depends on thousands of coordinated decisions and systems.

Questions this course answers

Why were several TBMs used on the Gotthard Base Tunnel?

Four machines worked on separated northern and southern sections, allowing parallel excavation and logistics.

How does a hard-rock gripper TBM brace itself while cutting?

Gripper shoes hold the machine against competent rock while hydraulic cylinders advance the cutter head.

What do the disc cutters on the head actually do?

Disc cutters fracture hard rock under high force; spoil is then removed by the machine's handling system.

Why is a breakthrough not the end of a tunnel project?

Excavation creates space, but many construction and commissioning stages turn it into a working railway.

What is the best way to understand the TBM's role at Gotthard?

The TBM made the excavation possible, but crews and systems made that excavation stable and usable.

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