What is Tunnel Boring Machine (TBM), Advantages and Features

TMB is used as an alternative to drilling and blasting
(DB) methods. TBMs are used to excavate tunnels with a circular cross
section through a variety of subterranean matter; hard rock, sand or almost
anything in between.

What is Tunnel Boring Machine (TBM), Advantages and Features

As the TBM moves forward, the round cutter heads cut into
the tunnel face and splits off large chunks of rock.  the cutter head carves a smooth round hole
through the rock — the exact shape of a tunnel. Conveyor belts carry the rock
shavings through the TBM and out the back of the machine to a dumpster. 
Tunnel
lining is the wall of the tunnel. It consists of precast concrete segments that
form rings, cast in-situ concrete lining using formwork or shotcrete lining.
A tunnel boring machine (TBM), also known as a
“mole”, is a machine used to excavate tunnels with a circular cross
section through a variety of soil and rock strata. They may also be used for
microtunneling.

What is Tunnel Boring Machine (TBM), Advantages and Features

They can bore through anything from hard rock to sand. Tunnel
diameters can range from a metre (done with micro-TBMs) to 19.25 metres to
date. Tunnels of less than a metre or so in diameter are typically done using
trenchless construction methods or horizontal directional drilling rather than
TBMs.
TBM excavate tunnels with circular c/s through a variety of
geological conditions.
Tunnel diameter can range from 1- 15 m.
One of the first TBM built was used for the construction of
Hoosac tunnel- Railroad tunnel in the Northern Berkshire towns of Florida and
North Adams Constructed of cast iron, it managed to drill 10 feet  before breaking down.
BMs are preferred in urban tunneling and underground mining
over conventional methods.

ADVANTAGES OF TBM

  • Reduced disturbance to the surrounding soil
  • Produce a smooth tunnel wall reducing ventilation
    requirements
  • Reduce cost of lining
  • Improved personnel safety
  • Working speed- 6 times greater
  • Hence, wherever speed and safety becomes the main  criteria, use of TBM despite its heavy
    capital cost is preferred.

What is Tunnel Boring Machine (TBM), Advantages and Features

MACHINE PARTS

A TBM typically consist of
Cutter head
Shield –metal cylinder serving as temporary support
structure while excavation
Trailing support mechanisms
• Precast concrete segment handling & installing devices
• Conveyor belt system for muck removal
• Control Cabin
• Supply tanks, exhaust fans etc.

TYPES OF TBM

Based on no. of shields used
1.Main beam TBM
2.Single shield TBM
3.Double shield TBM
Based on the face supporting technique used
1.Earth pressure balance TBM
2.Bentonite slurry TBM
3.Compressed air TBM

4.Fluid balance TBM

Saad Iqbal
Hi there, I am Saad Iqbal from Pakistan. I am an enthusiastic blogger, passionate content creator, construction geek, and a creative graphic designer. Connect with me at my social channels.