Geotechnical report_Morrison · 132008.169

Job No. ME09/068

2.0 THE INVESTIGATION
2.1 Method

A track mounted drilling rig was used to put down two boreholes at the top of the slope from
about RL50.0m (AHD) where large rig access was available. Both boreholes were taken
deep enough to intersect the basement geology (residual clay and sandstone). Sampling as
Standard Penetration Tests (SPT)' was carried out at 1.5m depth intervals. These boreholes
were taken deep enough to satisfy support loadings. On the east slope, access for the large
drilling rig was not possible and a small track mounted machine equipped with an SPT
hammer and rods was used to put down probes into competent support strata. Access tracks
to these test sites were cut by a 7 tonne excavator which was also used to assist the SPT
probe machine. The excavator was used to assist movement around the site.

The track mounted (Dando Terrier 2002) dynamic probing rig conducted Dynamic Probing
(DP) at 7 test sites (DP3 to DP9). Testing was continued to varying depths ranging between
1.80m to 7.70m below the ground surface.

The lower access track cut on the site exposed residual clay at the position as marked on the
site plan as test pit TP2.

At the swimming pool site tvo Dynamic Cone Penetrometer (DCP)? tests were taken.

2.2 Results

The borehole test pit and SPT probe positions are shown on the site plan included as
Appendix ‘A’ together with borehole, test pit, dynamic probe and DCP results.

In the normal SPT test the hammer blows are recorded in 150mm intervals. In the SPT
dynamic probe the blow count (or penetration resistance) was recorded for each 100mm of
cone penetration.

2.3 Test Positions

Test positions as shown on the site plan (Appendix A) were either measured from the east
boundary (BH1, BH2, DP6) or were located by GPS. Surface levels were taken relative to
survey level data provided on the existing east boundary masonry block wall.

2.4 Geology
2.4.1 Basement

The Regional Geology Map (Gympie Special Sheet 9445 Part 9545 [1999]), shows the
geology as the Tiaro Coal Measures sandstone which is seen in outcrop along the foreshore
between Sunshine Beach and Alexandra Bay. It was suspected that this geology also
represented the residual basement under what are now high sand dunes along the coastal
fringe. This basement was intersected in boreholes BH1 & BH2 and also in test pit TP2.

2.4.2 Teewah Sands

1 SPT - In this test a 63.6kg drop hammer falling 750mm is used to drive a steel sampler. The penetration resistance
of the sampler is measured as blows/150mm in three successive penetrations. The ‘N’ value is recorded as the sum
of the hammer blows for the last two 150mm penetrations.

2 DCP - In this test a 9.0kg drop hammer falling 510mm is used to drive a 30 degree tapered steel cone having a top
diameter of 20mm fitted to rods of smaller section.

 

Ref 00558 — Adrian Slinger MORRISON GEOTECHNIC
71 Seaview Terrace Sunshine Beach