tunneling shield is a protective structure used in the excavation of
tunnel. Shield used for the tunneling purpose are - single shield,
double shield or integrated shield. It is the geology or the nature of
the rocks and the soils that decides the kind of the shield for usage.
Double shielded tunneling boring machines are normally used in unstable
geology, or where a high rate of advancement is required. They are also
used for the workers protection in soft and unstable rocks. Double
shielded machines are also used to install a tunnel lining.
Behind the shield, there are various support mechanisms which are part
of the tunnel boring machines like dirt removal, slurry pipelines,
control rooms, rails for transport of the precast segments, etc. Apart
from this there are other equipments like rotating cutting wheel,
chamber hydraulic jacks etc that helps the machine for the excavation
The applications of all boring machines are nearly same. The difference
lies only in geology where they are applied. Followings are their
- Used for underground transportations like railways, cars, etc.
- For laying underground cables for various purposes.
- Used for excavating tunnels for various municipal operations etc.