Civil Engineering Reference
In-Depth Information
Table 9.1
Typical space provision and tolerances to account for in internal
cl
earances
Dimension
Typical value
Clearance for
A
n
×
3.65 m
+
hardstrip width
Traffic width: n
=
no. of lanes, 3.65 m is
typical lane width
B
5.25 m
5.0 m traffic height plus 0.25 m
allowance for loose flapping truck
tarpaulins
C
A
+
H
+
K
Total width required
D
B
+
E
+
F
+
G
+
L
+
M
Total height required
E
2.5%
Minimum carriageway crossfall
F
300 mm
Space for M&E equipment (excluding
vent fans which may require additional
space unless housed in niches)
G
75 mm
10 mm surface tolerance
25 mm settlement allowance
15 mm alignment curvature
25 mm element placing tolerance
H
80 mm
10 mm concrete surface tolerance
20 mm alignment curvature
50 mm element placing tolerance
I
As required
Space for equipment above footway—
not usually critical unless ventilation
fans are placed in this space
J
Width as footway
Height 2.3 m
Space for maintenance personnel access
and car passenger safety in the event of
breakdown
K
1.0 m
Minimum footway width
L
600 mm
Minimum depth of ballast to
accommodate drainage
M
75-100 mm
Two layers of wearing course with
allowance for overlay, unless it is
assumed renewal will include planning
out of the old surface
spatial provision that have been described and that need to be allowed for
a road tunnel. A typical set of tolerance allowances is given in Table 9.1.
Note that some of these values will vary, depending on the national design
code requirements.
Similar provisions must be made in the cross sections for rail tun-
nels, although the envelope may look quite different. This can be seen in
Figure 9.4, which shows the rail kinematic envelope used for the develop-
ment of the Bosphorus Tunnel for the Marmaray project in Istanbul.
