Appendix B- Geotechnical Investigation

Project No. 115-17158
April, 2015
Ref: 1-17158, 2015-04-08, BR VER 1                                                                      Page | 8
John Jamieson – GEOTECHNICAL INVESTIGATION - Proposed Residence, 38 Park Crescent, Sunshine Beach




                      pd        average effective overburden pressure
                      Ks 
                                 lateral earth pressure coefficient
                       
                                 pile-soil angle of friction
                      Nq 
                                 bearing capacity factor



(N q = 60 for medium dense sands, N q = 100 for dense sands)

Broms (1966) relates the lateral earth coefficient (K s ) and pile-soil friction angle ( ) to the
internal angle of friction of the soil ()and pile material as follows:
TABLE 2               LATERAL EARTH COEFFICIENTS
                                                                                             Ks
   Pile Material                                                 Loose                 Medium Dense   Dense
                                            o
       Steel                           20                          0.50                     0.75        1.00
      Concrete                      0.75 *                        1.00                     1.50        2.00
Note: Refer Table 3 for  values.

It should be noted that the calculated ultimate resistance of a given pile should also take into
account the installation effects of that particular type, i.e. whether displacement or non-
displacement pile performance can be expected.

Uplift and lateral capacities of piles are not considered, as these are both wholly dependent
on the specific pile type selected.

Steel screw piles involve a hollow steel stem with a flight attached to the toe of the pile which
are 'screwed' in the ground, reducing spoil and construction difficulties associated with loose
sands. The compression capacity is calculated based dominantly on the end bearing
capacity due to negligible shaft friction. Shaft capacity of screw-in piles are generally minimal
and should not be taken into consideration for calculating design values due to the nature of
pile installation. Steel screw piles should also be suitably protected from corrosion, eg.
galvanised, additional sacrificial wall thickness, concrete filled.

Preformed driven or pushed piles may also be suitable, however the environmental
constraints that may be present at this site might preclude driven piles due to the noise and
vibration associated with this method. Pushed-in piles avoid these problems, but a push-in
rig of sufficient reaction capacity may not be able to successfully negotiate the sloping site.
Specialist contractors should be approached if this pile type is considered.