Fill specifications - Geotechnical Investigation and Design Tables - page 216

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.