081128 - Lots 5 - 8 Soil Tests · OPW18/0155

                                 LOTS 5 TO 8, SETTLERS COVE, SERENITY CLOSE, NOOSA



Section 5.4 below provides advice and design parameters for retaining structures, however detailed design
and construction advice should be obtained from a specialist contractor. This should include potential impact
on adjacent buildings and services.
Design drawings provided by Tate indicate that a ‘working platform’ comprising a minimum 150 mm thick
layer of CBR15 material will be placed across the building area following bulk earthworks and compacted to
95% of the Maximum Standard Dry Density. Furthermore, the drawings indicate that assessment of the
subgrade shall be carried out by DCP testing following construction of the working platform.



5.2.2       Filling
The sand materials excavated from the site should be suitable for re-use as structural fill, provided any
deleterious and/or organic materials are excluded.
Fill should be compacted at moisture contents within the range of -2% to +1% of optimum moisture content
for Standard Compaction. 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 95% of the Maximum Standard Dry Density for cohesive soils, or 75% Dry Density Index (DDI) for
cohesionless soils.
Further details for control and testing of fill are given in Australian Standard AS 3798-1996 "Guidelines on
Earthworks for Commercial and Residential Developments".
Our experience in similar ground conditions indicates that the achievement of 75% DDI in ‘clean’ dune sands
will require the application of significant water and vibration, together with confinement of the layer under
compaction.



5.3       Footings
The results of our investigation indicate that medium dense (or denser) natural sands occur below about
0.4 m to 2.3 m depth across the site. Given the depth of the proposed basement excavation, such sands
should occur across the building subgrade level following bulk earthworks. Conventional high level strip or
pad footings may be used where there is a medium dense sand foundation. Strip or pad footings founded in
the medium dense sand may be designed using an allowable bearing capacity of 200 kPa, with resultant
settlements less than 25 mm.
Golder Associates should carry out inspection and testing of the foundations during construction in order to
confirm the allowable bearing capacity.
All footings should found such that they are not adversely affected by any adjacent excavations batter
slopes, trenches, or retaining walls that are not designed to support building loads. To minimise the potential
for any adverse interaction effects, footings should found at least below a plane extending 1 m horizontally
from the base of trenches/batter slopes/excavations/retaining walls, then rising up at 1V:2H, as illustrated in
the following diagram.




December 2008
Report No. 087682058 002 Rev.1                         4