Att 9 - Geotech and PASS report

                                                                                                        Page 3 of 13




In summary, the subsurface conditions encountered in the bores typically comprised pavement
materials and filling overlying natural silty and clayey sands then sandy and silty clays which are
further described below:
        Pavement materials: An asphalt wearing surface of between 30 mm and 50 mm thick was
         encountered in Bores 1 to 5. Underlying the asphalt surface in Bores 1 to 3, ‘very dense’ silty
         sandy gravel roadbase materials were encountered to between 0.18 m and 0.2 m depth.
        Filling: Relatively ‘medium dense’ to ‘dense’ clayey sand filling was encountered underlying the
         asphalt in Bores 4 and 5, and from the surface in Bore 6, to between 0.21 m and 0.7 m depth.
         Underlying the clayey sand filling in Bores 4 and 5, relatively ‘stiff’ sandy clay filling was
         encountered to 1.45 m and 0.75 m depth respectively.
        Sands: Underlying the roadbase and filling, typically natural silty sand was encountered in the
         bores with clayey sand encountered in Bores 4 and 5. The relative density of the sands typically
         were medium dense, becoming loose to medium dense with depth. The sands were encountered
         to between 2.8 m and 4.1 m depth in Bores 2 to 5, and to termination at 2.0 m depth in Bores 1
         and 6.
        Clays: Underlying the filling in Bore 6 between 0.7 m and 0.95 m depth, and interbedded within
         the silty sand in Bore 2 between 1.3 m and 1.55 m depth, an upper layer of soft to firm sandy clay
         was encountered. Beneath the sands at between 2.8 m and 4.1 m depth in Bores 2 to 5, silty clay
         was encountered. The strength consistency of silty clay was initially soft in Bores 2 and 3 to
         approximately 3.5 m depth, grading stiff and then very stiff with depth. The strength consistency
         of the silty clay was initially stiff in Bores 4 and 5, grading very stiff with depth. The very stiff silty
         clay continued to termination at 6.0 m depth in Bores 2 to 5.

Groundwater seepage was encountered at between 0.7 m and 1.45 m depth. It should be noted
however, that groundwater depths and ground moisture conditions are affected by climatic conditions
and soil permeability, and will therefore vary with time.




6.        Laboratory Testing

6.1       Plasticity and Particle Size Distribution Testing

Selected disturbed samples recovered from the bores were tested in the laboratory for engineering
properties of plasticity and particle size distribution for classification purposes. The results of this
testing are summarised in Table 1 with material test reports in Appendix D.

Table 1: Results of Plasticity and Particle Size Distribution Testing
Bore         Depth           Material          FMC             Plasticity             Particle Size Distribution
No.           (m)                               (%)                                               %
                                                         LL     PL      PI    LS    Gravel     Sand       Silt/Clay
                                                        (%)     (%)    (%)    (%)
     2       0.8-1.2        Silty sand          19.5      -      -     NP     0.0       0        95           5
     4       0.8-1.2    Sandy clay/clayey       13.0     29     15     14     7.5       3        65          32
                             sand



Geotechnical Investigation, Proposed Commercial Development                                     90151.00.R.001.docx
11-19 Hilton Terrace, Tewantin                                                                            May 2017