Geotechnical Report

    J000206-001-R-Rev0                                                                                  April 2016




Executive Summary
Core Consultants Pty Ltd (Core) has carried out a geotechnical investigation for a proposed aged care
facility at Walter Hay Drive, Noosaville.
This report provides geotechnical advice regarding site preparation, earthworks, footing design, and
pavement design parameters. A desktop assessment regarding acid sulfate soils (ASS) was also carried
out.
The subsurface investigation comprised eight (8 No.) test pits (designated TP1 to TP6; and TP-P1 to TP-P2)
excavated utilising an 8 tonne excavator to depths of 3.5 m below ground level. Test pits TP-P1 and TP-P2
were taken to 1.0 m depth to assess proposed pavement subgrade conditions.
The general subsurface profile encountered in the test pits comprised:
         TOPSOIL: comprising silty clay with traces of rootlets and organics to depths of between 0.1 m and
          0.3 m below ground level (BGL); overlying

         NATURAL SOILS: comprising stiff to hard silty clay to the depth of investigation of 3.5 m BGL; except
          in test pits TP1, TP3 and TP6 which encountered

         SILTSTONE: Extremely low strength, extremely weathered from depths ranging from 2.5 m to 2.8 m
          BGL to the depth of investigation (i.e. 3.5 m BGL).

Groundwater was not encountered in any of the test pits.
Site preparation will require clearing, stripping and grubbing. Fine rootlets and organics in the soils were
encountered in test pits up to about 0.3 m depth, however it is anticipated that grubbing of tree stumps and
tree roots will require localised stripping to greater depths. Root affected soils with tree roots up to about
50 mm to 100 mm diameter were noted in some of the test pits to depths of up to 0.6 m.

Earthworks should be generally carried out in accordance with Australian Standard AS 3798-2007
Guidelines on Earthworks for Commercial and Residential Developments.
The site classification is ‘Class ‘H2’ in accordance with AS2870-2011. The estimated ‘ys’ value for this site is
between 60 mm and 80 mm.
Building wall and column loads could be supported by strip or pad footing system suitable for a Class H2 site
classification. Footings should penetrate through any uncontrolled fill or unsuitable natural soils to found at
least 500 mm below platform level (750 mm below ground for articulated full masonry) and 200 mm into the
natural stiff (or stiffer) clay.
The following allowable bearing pressures may be adopted in natural materials for design purposes:
      -      Stiff clays:                                      100 kPa

      -      Very stiff clays:                                 200 kPa;

      -      Hard clays and extremely low strength siltstone: 400 kPa.

Laboratory CBR testing on the clay subgrade materials returned CBR values of 5 % to 9 %. Therefore,
based on our experience with similar materials, we recommend that preliminary pavement design should be
based on a CBR value of 5 % for the natural clayey soils.
Based on the investigation findings, it is our opinion that the presence of typical ASS materials is unlikely.
No excavation works are proposed below RL 5 m AHD. SPP14 therefore does not apply to the proposed
development. No further assessment of potential disturbance of ASS is required.




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