Fill specifications - Geotechnical Investigation and Design Tables - page 222

- DOS - Degree of Saturation.
-

If placement at EMC not practical then equilibration period, stabilisation or
zonation of material required.

- EMC can be wet of OMC for climates with rainfall > 1000mm, but dry of

OMC for rainfalls < 500mm.

17.17 Compaction layer thickness
•

The compaction layer thickness depends on the material type and equipment being
used. The operating space for equipment also needs consideration.

•

There is a “compact to 200mm thickness'' fixation in many specifications. This
assumes only light equipment is available and clay material.

Table 17.17 Compaction layer thickness.

Equipment size Material type

Rock fill Sand & Gravel Silt Clay

Heavy (

>

10 tonne) 1500 mm 1000 mm 500 mm 300 mm

Light ( 1.5 tonne) 400 mm 300 mm 250 mm 200 mm <

- Above assumes appropriate plant eg sheepsfoot roller for clays and grid rollers
for rock.

- Light equipment typically required behind walls, over or adjacent to services,

and in trenches.

17.18 Achievable compaction
•

The compaction achievable depends on the subgrade support below.

•

Lab CBR values and/or specified compactions may not be achieved without the
required subgrade support.

•

Typical achievable compactions with respect to layer thicknesses are provided for
a firm clay.

Table 17.18 Achievable compaction for a granular material placed over a
low strength support.

Relative compaction Thickness required to achieve density

(Standard proctor)

Minimum Typical

90% 100 mm 150 mm

92% 150 mm 225 mm

95% 200 mm 350 mm

97% 300 mm 400 mm

100% 400 mm 500 mm

102% 500 mm 550 mm