Appendix E_Geotechnical Investigation

                             PROPOSED UNIT DEVELOPMENT
                             PRECINCTS E2 & F, NOOSA SPRINGS

 6.2.2       Quantitative Assessment
In order to calculate the factor of safety (FOS) against slope instability for the proposed unit developemt
across Precincts E2 and F, numerical analysis has been conducted using the Slope/W computer program for
the assumed ‘worst case’ conditions. Based upon the results of our investigation and the 2000 SSE
investigation, the worst case profile through the site has been taken along an approximate north-east/south-
west alignment (down gradient) section line thorough Block H (within Precinct F). The ground slopes at
approximately 29° (55%) down from the gently sloping ridge plateau.

The ‘worst case’ soil profile comprises very loose to loose sands to a depth of 0.5 m BGL, overlying medium
dense (or denser) sands. In order to replicate possible loads from a single storey light weight structure, a
uniformly distributed load of 10 kPa has been applied at 1 m BGL to this model. Our recommendations are
that all footings are to be founded within the underlying dense sand. The Slope/W model replicates buildings
founded in the dense sand.

Groundwater was not encountered in any of the boreholes on the sloping part of the site, and was therefore
not included in the Slope/W model.

Results of the numerical slope stability analysis are illustrated in Text Figure 10. The key points from our
analysis are summarised as follows:

        Unit weight and shear strength parameters adopted for the soil strata were taken from the mid-range
         of values recommended for similar materials in Appendix D of Australian Standard AS4678-2002
         ‘Earth Retaining Structures’.
        Analysis was undertaken for a specified entry and exit zones, with a resulting minimum FOS value of
         1.5, with the result satisfying the generally accepted requirements slope instability (i.e. minimum
         FOS of 1.5).
Our analysis indicates that the proposed development will achieve at least the required minimum FOS.
Subject to implementation of the recommendations made in Section 7 during both operational and building
works, there will be a Low Risk of slope instability affecting the proposed development.




Text Figure 10: Slope W model



11 November 2015
Report No. 15193-002-Rev0                              11