Geotech 95141.00.R.001

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In order to improve the bearing capacity in the upper sand, where high level footings are being
considered, the upper loose sand would need to be densified. The base of all footings should be
individually compacted using a vibrating plate compactor to achieve a minimum density index of 70%. If
the sand is dry, it should be saturated and left for a short period prior to vibration. Should any loose
areas be encountered in the footing excavations the density of these areas would need to be improved.

Close supervision and testing by an experienced geotechnical engineer from DP during compaction is
suggested to ensure adequate uniformity of compaction is achieved. Testing using a dynamic cone
penetrometer (DCP) is recommended to check compaction using accepted density index correlation
tables.

The densification of the upper sand would allow high level strip and pad footings to be designed for an
allowable bearing pressure of 100 kPa.

Experience indicates that properly designed and constructed high level footings sized using the above
allowable bearing pressure are likely to undergo settlements in the order of 1% to 2% of the footing
width.

Where footings are located adjacent to underground services, the footings should extend to below invert
level for a distance of 1 m out from the trench. Beyond 1 m from the trench, the footings should be taken
to below an imaginary line drawn up at 45 degrees from the invert level. These requirements do not
override minimum structural footing base levels.

Alternatively, where development loads exceed the above allowable bearing pressure and estimated
settlements, a suitable deep foundation will be required. Given the presence of upper very loose to
loose sand encountered in the soil profile, selection of pile type and method of construction will need to
be considered. Most pile types could be considered, although bored piles would be prone to collapse in
the sand.

The ultimate geotechnical strength (Rd,ug) of piles can be calculated using the unfactored, ultimate shaft
adhesion and end bearing values given in Table 2. The Rd,ug values given will need to be multiplied by
a suitable geotechnical strength reduction factor (Ø g) to obtain the design geotechnical strength (Rd,g)
of piles.

If working stress methods are used in the pile design, the R d,ug values given in Table 2 will need to be
divided by a factor of safety of 2.5 to calculate the maximum single pile working load.

Table 2: Ultimate (Unfactored) Pile Design Parameters
                         Material                               Ultimate Unfactored             Ultimate Unfactored
                                                                  Shaft Adhesion*                   End Bearing*
                                                                       (kPa)                           (kPa)
               Very loose to loose sand                                    NR                                 NR
                  Medium dense sand                                         5                                 450
Notes: * Geotechnical strength reduction factor or factor of safety needs to be applied to these parameters
        NR = Not Recommended




 Geotechnical Investigation, Proposed Youngcare Facility                                                      95141.00.R.001.docx
 32 Viewland Drive, Noosa Heads                                                                                      January 2021