Appendix B - Geotech and Acid Sulfate report - MCU19-0030

Gympie Terrace Noosaville Pty Ltd




  6.6 Retaining structures
Permanent perimeter retaining walls for the basement structure could be designed using the parameters
given in Table 3. The values assume that the walls are fully drained, and no allowance is included for
hydrostatic pressures, construction loading, up-slope footing loadings, the effects of sloping ground and
backfill compaction stresses. Surcharge loads and hydrostatic pressures for non-drained walls will be in
addition to the wall loadings calculated using the parameters set out in Table 3.
Table 3: Retaining structure design parameters.
                                                                                  Lateral earth pressure coefficient
                                            Unit     Friction                                                Non-
                                                                 Cohesion,             Yielding
         Retained material                 weight     angle                                                yielding
                                                                  cu (kPa)
                                           (t/m3)   (degrees)
                                                                                     Ka
                                                                                                  Kp          Ko
                                                                                 (cantilever)
 Loose sand                                 1.7        27            N/A             0.41         2.46       0.58

 Medium dense (or denser) sand              1.9        33            N/A             0.3          3.33       0.45

 Notes:
 Ka - active; Ko - at rest; Kp - passive

 For yielding walls active state develops when: Deflection > 0.001H to 0.004H (granular soil),
 or deflection > 0.01H to 0.04H (cohesive soil)


  6.7 Drainage
Site grades should shed water and prevent ponding. Subsurface drains adjacent to slabs and pavements are
recommended.
Collection/cut-off drains should be installed up-slope of all excavations, and surface run-off should be
prevented from entering excavations.

  6.8 Aggressivity of soils
Chemical analysis can provide an indication of the potential for long term damage to foundations, buried
pipelines, in-ground structures, services and other infrastructure. Soil texture is also important in this regard,
as granular soils allow oxygen exchange (oxidation) to occur more readily and are also more permeable.
Australian Standard AS 2159-2009 Piling - Design and installation provides the range of exposure
classification of the surface of steel piles and concrete piles based on the range of chemical conditions in the
soil and the possibility of changes in groundwater levels.
The results of laboratory analysis undertaken on the sand sample from borehole BH1, indicates an exposure
classification of ‘Mild’ to ‘Non-Aggressive’ in accordance with Table 6.4.2(C) and Table 6.4.3(C) of AS 2159-
2009.



J000799-002-R-Rev0                                                                                         Page 8