Table 6.1 – Grading of bedding material
-
A.S. sieve (mm)
|
Percentage passing by weight
|
Bedding sand
|
5 – 7 mm screenings
|
9.50
|
|
100
|
6.70
|
|
85 - 100
|
4.75
|
100
|
30 - 85
|
2.36
|
80 - 100
|
0 - 30
|
1.18
|
|
0 - 5
|
0.075
|
0 - 15
|
|
Pipe support: Use identical bedding material for pipe underlay, side support and overlay. Place pipe on a minimum 75 mm thick compacted underlay. Extend bedding material to provide a minimum cover of 150 mm over the conduit.
Draw rope: For electricity and telecommunications conduits, provide a 4 mm diameter synthetic polypropylene filament rope. Install draw ropes with a minimum of 1.5 m of slack in each pit and rope ends firmly secured to prevent the ends being lost in the conduit. Provide joints in the rope capable of resisting the same tensile load as the unjointed rope and that do not appreciably increase the diameter of the rope.
End plugs: Plug or cap the ends of all conduits with suitable fittings to prevent the entry of foreign matter.
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