Appendix H Geotechnical Investigation - 14-16 Mary Street, Noosaville - Bounce Hostels 15.6.2018

J000605-001-R-Rev1                                                                                                March 2018


                                               TRENCH BACKFILL
      GROUND LEVEL




                                                                           FOUND FOOTINGS
      TRENCH SIDEWALL                                                      BELOW THIS LINE
                                                                    45°


                                                   1.0m
                                                             1.0m



       SEWER / STORMWATER PIPE




6.6        Retaining structures
Permanent perimeter retaining walls for the basement structure could be designed using the unfactored
parameters given in Table 1. Hydrostatic pressures for non-drained walls, construction loading, up-slope
footing loadings, the effects of sloping ground and backfill compaction stresses must also be considered in
the retaining structure design.
Table 1: Retaining Structure Design Parameters.
                                                                                    Lateral earth pressure coefficient
                         Unit       Saturated        Friction
   Retained                                                      Cohesion,
                       weight       unit weight       angle                             Yielding              Non-yielding
   material                                                       cu (kPa)
                       (kN/m3)      (kN/m3)         (degrees)

                                                                                 Ka (cantilever)      Kp            Ko
Medium dense
                          19              21           30              -              0.36           2.77           0.53
or dense sand
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)

Use saturated unit weight for soils below the water table and within the capillary fringe above the water table



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.

7.0       ACID SULFATE SOIL ASSESSMENT
7.1            Background
The development of ASS is commonly the result of marine or estuarine deposition of sulfate and iron bearing
sediments in the presence of an abundant source of readily decomposable organic matter resulting in the
deposition of pyrite. This pyrite is stable within the soil so long as anoxic conditions prevail. Oxidation of this
material produces acidic conditions and oxidation typically occurs as the material is exposed above the water
table by excavation, and by lowering the water table during dewatering processes.


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