MCU14/0106 Appendix E - Engineering Report

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August 2004 -T- 04682104(AB)

 

dependent upon the prevailing weather conditions prior to, and during, construction. Care
should be taken with open excavations as any surface water that ponds on the site soils may
cause rapid softening.

We anticipate that ground water seepage should controllable by the installation of up slope
diversion drains (swales), and possibly shallow subsurface drains, graded to discharge away
from the work area and possibly temporary sump pumps. Any ‘wet’ areas should be
permanently drained and connected to external drainage outlet points.

In order to minimise potential shrink-swell soil movements beneath buildings and pavements
across the proposed fill areas, it would be prudent to separate sand and low to medium plasticity
sandy clay materials won from proposed excavations (generally upper 1 m of soil profile) from
the medium to high plasticity clay soils and then stockpile these materials separately. These
lower plasticity materials should then be placed in the upper layers of any fill. We suggest a
minimum 1 m depth cover of sand and / or low to medium plasticity materials in fill.

6.1.3 Filling

The sand and clay soils won from the proposed excavations should be suitable for re-use as fill
subject to placement in accordance with the following guidelines.

Other than for clay pond / basin liners (ref. Section 6.1.4), fill should be compacted at moisture
contents within the range of -2% to +0.5% of optimum moisture content for Standard
Compaction. Confirmatory testing must be carried out at regular intervals. Further details for
control and testing of fill are given in Australian Standard AS 3798-1996 “Guidelines on
Earthworks for Commercial and Residential Developments". +

Select fill should have a maximum particle size of 100 mm for an uncompacted layer thickness
of 200 mm and should be compacted by repeated rolling to achieve a dry density ratio of at least -
98% of the Maximum Standard Dry Density for cohesive soils, or 75% Dry Density Index for
cohesionless soils. ‘Level 1’ earthworks control in accordance with AS3798-1996 is
recommended.

In accordance with good construction practice, fill embankments should be ‘over built’ then
trimmed back to the well compacted material.

Subject to fill placement as specified above, we estimate that total long-term settlement of fill
platforms (up to about 3 m height) should not exceed 10 mm.

Based upon our experience with similar materials, we anticipate a bulking factor range of 0.95
to 1.05 for the fill. This bulking factor is a ratio of in situ soil density to compacted soil density,
at 98% Standard Compaction, and does not include allowance for handling losses (eg. from
wind and rain),

Golder Associates