Attachment 5 - Geotechnical Assessment · MCU18/0015

 

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RTI 117055 Folio B388 ~~

 

November 2003 -4- 03632248-001

 

4.2. Laboratory Testing

Disturbed samples were tested for classification purpose by Geotech (S.C.) Pty Ltd to
determine:

¢ Soaked (4 day) CBR with 100% Standard Compaction (2 No.);
* Particle Size Distribution (PSD, 5 No.); and
e Atterberg Limits and Percent Fines (< 0.075 mm, 2 No.).

Golder Associates’ Mansfield laboratory conducted material strength testing on disturbed
sand and undisturbed clay samples, as follows:

e Direct Shear on sand remoulded at 70% Density Index (2-No.); arid

e  Triaxial Shear Test on undisturbed clay, CUM with pore*pressure measurements (1 No.).
Results are summarised in Section 5.2 below aptheect reports are presented in Appendix B.
5.0 INVESTIGATION FINDINGS

5.1 Geology & Subsurface Conditions

Published geological information’ indicates that the majority of the site is underlain by a
Quaternary (Pleistocen¢) age quartz sand dune, with Jurassic to Cretaceous age Noosa Quartz
Diorite to the east of the.creek and probably underlying the sand dune at depth.

The subsurface conditions encountered in the boreholes and test pits are variable as shown in
Sections A-A to D-D (Figures 2 to 5). Boreholes BH1 to BH4/4A encountered very loose to
loose dune sands to depths of between about | m and 3 m, overlying medium dense sand,
over dense sand below.about 3 m to 4 m down to the full depth of the boreholes.

Boreholes BH5 and BH6 encountered loose to medium dense sand, then DCP refusal at about
1 mto 1.5 m depth. Test pits TP5 and TP6 dug adjacent to the boreholes encountered very
loose to loose dune sand, containing some diorite gravel, cobbles and boulders up to 300 mm
across, overlying dense to very dense colluvium comprising about 30% grey to dark grey silty
sand and 70% diorite (extremely weathered to distinctly weathered, very low to medium
strength gravel and cobbles). Diorite cobbles and boulders up to 400 mm across were
excavated from Test Pit TP5, between 1.7 m and 2.2 m depth, where refusal of the excavator
bucket occurred. A massive shelf of diorite was noted in the creek bed about 10 m to the
north-east of test pit TPS. Refusal on diorite cobbles and boulders occurred immediately

' 1:100,000 Geological Map, GYMPIE SPECIAL, Sheet 9445 & Part 9545, DME, 1999

Golder Associates