Reference Documents - OPW24-0098

                                                                                                         PTG Consulting
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high and a фg value of 0.40 would apply. Where an allowable bearing pressure is required, a factor of safety of
3 should be adopted.

The above parameters are only suitable where the excavation of piled foundations are supervised and at a
minimum inspected by a suitably qualified geotechnical engineer to confirm the founding conditions and
materials encountered in the side walls.

The design of piled foundations should be undertaken in accordance with:
• AS2159-2009: Piling - Design and installation;
• Any other relevant design standards (Australian or international); and
• Engineering Principles.

The piled foundation design should also consider:
• Piles should be founded a minimum of two pile diameters into the nominated strata and have a minimum
    pile length of four times the pile diameter;
• The upper 1 m of pile length should be ignored due to pile load development and shrink swell effects; and
• Settlement of properly designed and constructed footings should be less than 1% to 2% of the pile diameter.

To calculate the design geotechnical strength (Rd,g), the ultimate geotechnical strength should be multiplied by
a suitable geotechnical strength reduction factor (фg) as per Section 4 of AS 2159–2009. The geotechnical
strength reduction factor (фg) is based on:
• фgb = The basic geotechnical strength reduction factor, calculated using a risk assessment procedure;
• фtf = Intrinsic testing factor, based on the type of pile testing adopted; and
• K = The testing benefit factor, based on a percentage of the piles that are tested.

Typically, where no pile testing is undertaken and the piles have a low redundancy, the assessed risk rating would
be high and a фg value of 0.45 would apply. Where an allowable bearing pressure is required, a factor of safety
of 2.5 can be adopted. Specialist piling contractors should be consulted when selecting and installing piles.


12. LIMITATIONS
It should be noted that the test sites simply give a representation of what the soil profile is expected to be across
the entirety of the site. However, it is possible for the soil profile to differ at other locations within the site and
due to this Protest Engineering requires notification of any varying conditions that are found during construction
as it may alter the assumptions and models adopted within this report.




PTG/00259 – 25 Wyuna Drive, Noosaville              Page 12 of 15                                        28 June 2024