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General terms
3D View
Roads - General
Term/Expression
Chainage or station
Design Profile
Excavated Profile
Underbreak
Overbreak
Tunnel Portal
Tunnel Face
Superelevation (Rotation)
Rotation Point
g
h
a
d
b
Tunnel_001
a
b
Tunnel_002
Description
The cumulative distance along the centreline,
frequently but not always starting at zero.
Geometric description of the designed shape
of the cross-section of the tunnel. The
design profile can contain straight or curve
elements.
Shape of the cross-section of the tunnel that
has been excavated.
When the excavated profile is inside the
design profile, the underbreak is the perpen-
dicular distance between the design profile
and the excavated profile.
When the excavated profile is outside of the
design profile, the overbreak is the perpen-
dicular distance between the design profile
and the excavated profile.
The open end of a tunnel.
The point where the excavated tunnel meets
existing terrain.
Angle of rotation of a design profile. Used to
take into account the velocity of a moving
vehicle through a curve.
The point about which the design profile is
rotated. This point may or may not coincide
with the centreline.
e
f
a
Centreline
b
Centreline offset
c
Point on design profile
d
Centreline height offset
e
Design profile
f
Excavated profile
g
Underbreak
c
h
Overbreak
a
Centreline or axis
b
Tunnel portal
c
Tunnel face
c
699
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