IntermediateTopic 42 of 112Civil & Structural
Tunnelling and excavation
Methods to build underground spaces while controlling ground movement.
In depth
Excavations need support (sheet piles, diaphragm walls, soil nailing) and dewatering. Tunnels are driven by TBM, NATM/sequential excavation or cut-and-cover; lining by segments or shotcrete. Ground movements and settlement are controlled with face pressure and monitoring.
Key points
- Ground loss and volume loss
- Rock mass classification (RMR, Q)
- Ventilation and safety
ExampleThe Channel Tunnel was bored by several TBMs working from both sides.
What is Tunnelling and excavation?
Methods to build underground spaces while controlling ground movement.
Why is it important to understand tunnelling and excavation?
Tunnelling and excavation methods control ground movement, which protects nearby buildings and utilities during underground construction.
What is the main risk in tunnelling?
Ground loss and settlement of the surface above, which can damage buildings and services if not controlled.
What is a tunnel boring machine?
A machine that excavates and supports a tunnel at the same time, which is efficient for long tunnels in soft to hard ground.
How is Tunnelling and excavation used in practice?
Typical applications include choosing a tunnel boring machine for a city metro line, using sheet piles to support an excavation next to a road and planning the sequence of a deep basement dig to limit movement of neighbours.
What should I learn before Tunnelling and excavation?
Study "Liquefaction" first (topic 41 of 112 in Civil & Structural). It covers the groundwork this topic builds on.
What are the key points of Tunnelling and excavation?
Ground loss and volume loss. Rock mass classification (RMR, Q). Ventilation and safety.
Can you give an example of Tunnelling and excavation?
The Channel Tunnel was bored by several TBMs working from both sides.
What comes after Tunnelling and excavation?
The next topic is "Statically determinate structures", which builds directly on this one.
How difficult is Tunnelling and excavation?
It is classed as Intermediate in Civil & Structural (topic 42 of 112). It is an intermediate topic. Work through the beginner topics in Civil & Structural first.