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About Tunnelling
Why
go underground
How
to go underground
Use
of underground spaces
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Histories
Main glossary
Invert
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Term
Definition
Invert
The lowest section of a
tunnel
, i.e., the
floor
. On a circular configuration, it is approximately the bottom 90 degree of the arc of the tunnel. On a square-bottom configuration, it is the bottom of the tunnel.
