Reference Document - MCU24/0023

GJ Gardner Homes Gympie                                                                         23236-001-Rev0
C/- Covey Associates Pty Ltd                                                                      7 August 2023

4.2.3 Filling
Site soils where free of deleterious materials (e.g. vegetation, oversize etc.), are expected to be suitable for
re-use as structural fill, subject to appropriate moisture adjustment. It should be noted that placement of
highly reactive clays could be difficult and impacts on site classification and pavement design should be
considered.
Should importation of fill be required, it is recommended that such fill should comply with the following:

          Minimum CBR of 10%
          Maximum plasticity index of 15%
          Shrink-swell index ≤ 1%
          Maximum particle size of 100 mm

Controlled fill materials should be compacted at moisture contents within the range of -2% to +2% of OMC for
Standard Compaction. Confirmatory testing must be carried out at regular intervals and further details for
control and testing of fill are given in Australian Standard AS 3798-2007 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 shall be compacted by repeated rolling with a small
compactor to achieve a dry density ratio of at least 95% of the Standard Maximum Dry Density for cohesive
soils, or 70% Dry Density Index for any imported cohesionless soils.
Fill must be ‘benched’ into the natural soil, over-filled by 0.5 m (horizontally) and then trimmed back to the
well compacted material.

4.3       Footings
All footings for the proposed residence and ancillary structures must penetrate through any fill (existing and
future) and natural soils to found at least 0.5 m into low strength (or stronger) phyllite. Based on the GD
boreholes, founding depths of about 1 m to 1.5 m BGL are anticipated. It is therefore recommended that the
building should be supported on bored piles or ‘bucket piers’.

Footings so founded may be designed using an allowable bearing pressure of 250 kPa.

Footing design should also account for potential soil reactivity, advised by GD to be equivalent to Class M. It
should be noted that the placement of highly reactive clays, such as the onsite materials may result in a
more adverse site classification.

All footings should found such that they are not adversely affected by any adjacent excavations, trenches,
retaining walls, or in ground structures that are not designed to support building loads. Where footings are
located within a horizontal distance of 1.5H (H being the batter height) of any cut or fill batter crest, these
footings must be founded at a depth level with the toe of the batter. Footings should found at least below a
plane extending 1 m horizontally from the base of trenches/excavations/retaining walls, then rising up at
1V:1H, as illustrated in in Text Figure 13 overleaf.




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