Geotechnical Investigation

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                                                                                                       arcosgroup.com.au
                                                                                      Sunshine Coast | Brisbane | Gold Coast




8.1       FOOTINGS
In accordance with industry standards, a geotechnical engineer from Arcos should undertake the testing within the
footings to confirm that the encountered material is in alignment with the adopted parameters and assumptions
provided within this report. Where this does not occur, Arcos cannot be held liable for any of the information presented
within this report.
All footings will need to be designed to accommodate potential ground surface movement, settlement values and
any additional settlement values associated with the placement of new fill.
Settlement for suitably sized and designed high level footings should be in the order of 1-2% of the width of the
footing.
If footings are located adjacent to an underground service or other obstruction that is not homogenous with the
founding strata, the footing should be extended a minimum 0.3 m below an imaginary line projected at a 45 degree
angle from the lowest point of the service/obstruction. This is depicted graphically for reference:




The ultimate geotechnical end bearing and shaft adhesion parameters are presented in Table 2. The values given
will need to reduced by applying a suitable geotechnical strength reduction factor (Φg) for limit state or divided by a
suitable factor of safety for working stress methods. The Φg should be selected by the designer.
Based on the conditions encountered, high level footings or bored piles would be considered suitable


TABLE 2: DEEP LEVEL FOOTING – ULTIMATE GEOTECHNICAL PARAMETERS (LONG PILE)

                  Material                                     Bored                                Bored

                                                             Fb (kPa)                             Fs (kPa)
                   Stiff Clay                                    450                                  20
                Very Stiff Clay                                  900                                  45
 Notes: Fb = Base Bearing (Ultimate); Fs = Shaft Adhesion (Ultimate)


The upper 1 m of soil profile should be ignored in shaft calculations for bored piles to allow for shrinkage cracks. Due
to installation disturbance, shaft adhesion should be ignored for steel screw piles. The values presented in Table 3
assume that the material equal to four pile diameters below the base of any footings is as strong or stronger.



Sunshine Coast | Brisbane | Gold Coast