Geoscience Reference
In-Depth Information
Table 17.5
Granular materials for pipe beddings.
Pipe size
Maximum particle size
100 mm
10 mm
<
100-200 mm
15 mm
200-300 mm
20 mm
300-500 mm
30 mm
>
500 mm
40 mm
•
Proper compaction at the haunches of pipes is difficult to achieve and measure.
-
Pipes are usually damaged during construction and proper cover needs to be
achieved, before large equipment is allowed to cross over.
-
Typically 300mm minimum cover, but 750mm when subjected to heavy
construction equipment loads.
17.6 Compacted earth linings
•
The key design considerations for earth linings are adequate stability and
impermeability.
•
The low permeability criteria requires the use of materials with
>
30% clay
fines.
•
Density of 95% of Standard Maximum Dry Density typically used.
•
Control Tests of at least 1 per 1000m
3
placed would be required.
Table 17.6
Typical compacted earth lining requirements.
Depth of water
Canal design
Side slope (1V :H)
Side thickness
Bottom thickness
0.5 m
1V :1.5 H
0.75 m
0.25 m
≤
1.5 m
1V :1.75 H
1.50 m
0.50 m
3.0 m
1V :2.0 H
2.50 m
0.75 m
17.7 Constructing layers on a slope
•
Inadequate compaction may result at the edges or near sloping faces. Large equip-
ments are unable to compact on steep slopes. Layers are placed either horizontally
or on a minor slope. Benching may be required to control the water run off, and
hence erosion.
•
Proper compaction requires moisture content of soil near to its plastic limit.
•
The thickness of placed layers is typically 0.40m (compacted) for a 10 tonne roller,
but depends on the type of material being placed.
•
The thickness of placed layers is typically 0.20m (compacted) for 3 tonne roller.
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