Reference Document - OPW25 0085 (AS Published)

4.9           Geotechnical Laboratory Test Results
Table 2 below summarises the results of laboratory classification testing conducted on two soil samples
recovered during the investigation. Full test results (laboratory certificates) are presented in Appendix B.

Table 2: Summary of Quality of Materials Testing

                                                           Atterberg Limits
   Test Pit                                                                         Linear     Percent
                  Depth (m)       Liquid Limit         Plastic       Plasticity
     No.                                                                          Shrinkage   Fines (%)
                                      (%)             Limit (%)      Index (%)
                                                                                     (%)
      TP1          0.5 – 0.7            30                 17           13           7.0          28
      TP8          0.4 – 0.7            61                 33           28           8.0          83
Notes: % fines denotes percent passing 0.075 sieve;

Laboratory testing indicates that the residual sample (sandstone origin) tested from Test Pit TP1 was a
clayey sand with low plasticity fines. The residual sample (siltstone origin) tested from TP8 was a clayey
silt with a high liquid limit. As such the clayey silts/silty clays encountered across the majority of the
property are estimated to have a moderate to high potential soil reactivity to normal moisture content
changes.
CBR testing was completed on the clayey silt sample from TP8 located within the proposed road
alignment, and returned a CBR value of 6% which is typical of those often achieved in the laboratory for
silty soils. However, the materials are expected to be susceptible to strength loss particularly if they
become wet, with much lower CBR values likely for materials even just slightly moist of optimum
moisture content (OMC) for compaction. The field moisture content of the sample tested was 4.8 % wet
of OMC. Testing indicates that subgrade moisture conditioning (drying back) will likely be required
during construction. It is noted that the samples had negligible swell recorded.




Geo-Environmental Investigation for Proposed Subdivision
7 February 2025 | 24386-001-Rev0                                                                             11