Geotechnical Investigation Report

The site can however be re-classified, and this re-classification is provided below, assigning an equivalent site class in
response to normal soil moisture conditions. The estimated characteristic ground surface movement in normal soil
moisture conditions for the site is expected to be between O mm and 20 mm, consistent with a ‘Class S’ site.

This classification is relevant to sites subject to normal moisture conditions. Abnormal moisture conditions, such as
from the removal or planting of trees (including on adjacent sites), poor site drainage, and development of gardens
adjacent to the footings, may cause higher movements to occur, probably resulting in damage, which may or may not
be within acceptable limits. It is noted that characteristic ground surface movement for the site is based on the existing
soil profile, and the moisture content changes withing soils due to normal seasonal variations. It does not consider soil
settlement under building foundation load.

6.3 FOUNDATIONS

Based on an interpretation of the typical structural loads anticipated, basement levels for the building and subsurface
conditions encountered during the investigation, both high level and piled foundations could be considered as suitable
for the development. Discussion on the suitability of high level foundations can be found in section 6.3.1 below.

Based on the information available at the time of writing this report, general design parameters and recommendations
have been provided in the subsections below which can be used for design of the foundation system of the structure.
The design of the structure must consider the structural loads against serviceability.

All footing excavations should be inspected by PTG to confirm that bearing pressures have been achieved, and
footings are clean and free from loose and/or water softened materials.

6.3.1 HIGH LEVEL FOUNDATIONS

Preliminary design of high-level pad footings up to 3m wide or strip footings with a minimum 0.5m depth can be
designed using the allowable bearing pressures in Table 2. Elastic settlements of properly designed and constructed
high level footings are usually in the order of 10 mm for 0.5m wide strip footings to 25 mm for large square pad
footings up to 3 m wide.

It is anticipated that the ground conditions at basement foundation level across the majority of the buildings footprint
will comprise medium dense or denser natural sands. Where medium dense natural sands are present at basement
foundation levels, PTG’s below preliminary design of high level footings can be considered suitable.

If any areas of uncontrolled fill or loose soils are found to be present at basement foundation levels, these would not
be considered as suitable founding soils for the below high level footing design, and are suggested to be removed and
replaced with engineered structural fill, in accordance with '‘AS3798-2007 Guidelines on Earthworks for Commercial
and Residential Developments’.

Table 2: Allowable Bearing Pressures for High Level Footings

Material Type Allowable Bearing Pressure (kPa)

‘Uncontrolled’ fill Not Recommended
‘Controlled’ fill 100

Loose sand Not Recommended
Medium dense sand 100
Dense sand 200

It is noted that in sand soils, bearing capacity increases with footing base depth. While suitable bearing capacity may
be achieved in loose sands be designing the footings at greater depths, high level footings are not recommended on
loose sands due to the potential for instantaneous settlement of foundations.