Geotechnical Report

 J000206-001-R-Rev0                                                                                      April 2016


4.0       METHOD OF INVESTIGATION
             Fieldwork
The investigation fieldwork was carried out on 22 March 2015 and comprised eight (8 No.) test pits
(designated TP1 to TP6; and TP-P1 to TP-P2) across the proposed development footprint. The test pits were
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.
Dynamic cone penetrometer (DCP) testing was carried out adjacent to each test pit to help assess soil
density or consistency. Disturbed and/or undisturbed (U50 tube) soil samples were recovered from the test
pits for subsequent laboratory testing.
All fieldwork was carried out in the presence of geotechnical engineering staff from Core, who also logged
the subsurface conditions in accordance with Australian Standard AS1726-1993 Geotechnical site
investigations.
Test pit locations were recorded with a hand held GPS device with a reported accuracy of +/- 5 m and are
shown on Figure 1. Test pit surface elevations were inferred from ground surface contour information
provided to us by the client. Test pits were backfilled upon completion with excess spoil mounded at the
surface.

Results of the fieldwork are presented in the Reports of Test Pits in Appendix A, along with explanatory
notes. Sub-surface conditions are discussed in Section 5.2.4.2 Laboratory Testing & Results

             Laboratory Testing
Selected soil samples were forwarded to the NATA accredited laboratory of Geotech (S.C.) Pty Ltd for
classification testing comprising Atterberg limits, particle size distribution and shrink-swell index analysis to
assess site reactivity. California Bearing Ratio (CBR) testing was carried out for pavement design purposes.

Test certificates are given in Appendix B. Tables 1 and 2 summarise the results of laboratory testing.

Table 1: Summary of Classification Testing

                                   Soil Description     Percent     Plasticity     Liquid                    The
                                                       Fines (%)    Index (%)     Limit (%)     Shrink
                  Depth
  Test Pit                                                                                      Swell
                       (m)
                                                                                                Index
                                                                                                 (%)
                       0.3                                93           70            48
    TP1                               Silty CLAY                                                   -

    TP2                0.9            Silty CLAY          99           78            55            -

    TP3           0.6-0.85            Silty Clay             -          -                -        3.8

results indicate that the clay materials are high plasticity and highly reactive to moisture content variation.
The shrink-swell index results are further discussed in Section 6.2.1.
Table 2: Summary of California Bearing Ratio (CBR) Testing

                   Depth                                                    Compaction           Soaked CBR
                                                         Field
                                                        Moisture   Maximum        Optimum
  Test Pit      From         To     Soil Description                  Dry         Moisture     Swell      CBR
                                                        Content
                 (m)         (m)                          (%)       Density       Content       (%)       (%)
                                                                     (t/m³)         (%)
   TP-P1         0.2         0.3    Silty Sandy CLAY      26.2        1.607         21.1        2.6        5.0
   TP-P2         0.2         0.5    Silty Sandy CLAY      24.2        1.633         20.8        1.5        9.0


CBR testing on the existing natural materials returned values of 5 % and 9%. The CBR results are further
discussed in Section 6.3.




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