Geotechnical report_Morrison · 132008.169

Job No. ME09/068

Sand ridges on the Sunshine Beach coastline have formed on the Teewah sands which are
exposed in places as cemented sand (coffee rock). The best exposures of Teewah sands are
on the Cooloola coast at Rainbow Beach and at Fraser Island locally known as the coloured
sands. Wind blown dune sand covers the Teewah sands on this site.

BH1 and BH2 intersected loose wind blown dune sand to depths of 5.2m (BH1) and 3.8m
(BH2), or to RL44.8m and RL46.3m respectively, when the Teewah medium dense sand was
intersected, first brown grading to dense and very dense then yellow below RL37.8m (BH1
and RL42.0m (BH2). On the slopes below, surface dune sand was found in the southern part
and in the northern part the Teewah sand, and the residual basement geology dominated.
Test pit TP1 was dug into yellow sand and test pit TP2 only 10 metres north found residual
extremely very low strength sandstone (hard sandy clay).

SPT dynamic probe profiles are not described. It appears that the low penetration resistance
near the surface represents wind blown dune sand while at depth medium dense to dense
sand (Teewah sand) or residual clay and extremely low strength sandstone is inferred.

Summary of Boreholes Probe and Test Pits

 

 

 

 

 

 

 

 

 

 

 

 

Borehole | Surface Level Depth of Depth of Top of
Probe (m) AHD Loose Dune | Teewah Sand Residual

Test Pit Sand (m) (m) Basement as
No. RL (m)
BH1 50.0 5.2 9.7 35.1
BH2 50.15 3.8 10.4 35.9
DP3 45.9 3.1 - -
DP4 48.1 0.6 - -
DP5 41.4 3.0 - -
DP6 42.9 0.4 - -
DP7 40.9 2.6 - -
DP8 41.4 1. - -
DP9 43.3 2.3 - -
TP4 41.0 - - -
TP2 42.0 - - -

 

 

 

 

 

 

 

3.0 GEOTECHNICAL CONSIDERATIONS
3.1. Excavations

All materials found on this site within the proposed excavation depth will be rippable with
medium sized plant to form the building platforms for the two living levels with a cut depth of 4
to 5 metres to the top bench and a cut of a similar depth to form the lower bench.

The natural slope at about 20-25 degrees would not prevent the operation of normal plant.

Care should be taken on the steep platform edges. However, it is not expected that any
temporary retaining of the fill edges will be required.

3.2 Retaining the Cuts

The top cut can be retained either as:-

1. Abatter in sand at 30 degrees which would preferably be wet down and covered
with shotcrete if a steeper cut (say 40°) was required.

2. Athin steel sheet pile vertical wall anchored into the slope or

 

Ref 00558 — Adrian Slinger MORRISON GEOTECHNIC

71 Seaview Terrace Sunshine Beach