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Tunnel profiles
Roads - General
Distance along a particular element
By the distance along a particular element of the design profile and an offset
from the element.
b
d e
c
a
Tunnel_006
Staking tunnel profiles
Tunnel profiles are normally staked after excavation to indicate the position of
tunnel design elements or services such as lighting or ventilation.
Basic terms
Usually a tunnel under construction is designed and built in various stages such
that a given chainage can have various design profiles. For example shotcrete
or final lining. Each design profile is called a layer.
b
c
a
Tunnel_007
Measuring tunnel profiles
Tunnel profiles are normally measured after excavation to compare the excava-
ted profile with the design profile. This check can occur during the excavation
phase of the project or for quality control checks of the built tunnel.
When measuring tunnel profiles, it is possible to scan various profiles from one
instrument position. The profiles to scan are defined with respect to a defined
chainage. Profiles can be scanned at a given forward and back interval within a
given forward and back distance from the defined profile.
a
Centreline
b
Point on tunnel face to stake
c
Element of design profile to stake
d
Distance from start of design pro-
file element
e
Offset perpendicular to design pro-
file
a
Centreline or axis
b
Final lining
c
Shotcrete
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