1 - GEOTECHNICAL INVESTIGATION REPORT - 150320 LAR Road Investigation Ridgewood Geotech 23042015_Rev1-Combined

4. 1 Auger Holes
A series of auger holes were drilled at approximately 200 m centres along the length of the
proposed road upgrade. Seven auger holes were drilled in total through the existing
pavement gravels into the underlying subgrade. The auger hole locations were recorded
using a hand held GPS unit using the WGS84 coordinate system. The locations of the
auger holes are provided below:

• AH15-01 - 486366E; 7074117N - Auger hole located 2 m inside southern edge
• AH15-02 - 486184E; 7074129N - Auger hole located 1.5 m inside northern edge
• AH15-03 - 486014E; 7074020N - Auger hole located 1.5 m inside western edge
• AH15-04 - 485872E; 7073861N - Auger hole located 1.1 m inside eastern edge
• AH15-05 - 485841E; 7073708N - Auger hole located 1.8 m inside western edge
• AH15-06 - 485713E; 7073520N - Auger hole located 1.2 m inside northern edge
• AH15-07 - 485533E; 7073491N - Auger hole located 1.8 m inside southern edge

Samples were taken of selected pavement materials and subgrade soils for potential use in
laboratory testing. Dynamic Cone Penetrometer (DCP) testing was undertaken at selected
auger hole locations to aid in soil strength characterisation.

All auger hole drilling was carried out under the direction of a senior geotechnical engineer
and traffic controllers working to a council approved traffic management scheme.

The termination depth of auger holes ranged between 0.15 m (AH15-07) and 1.5 m (AH15-2
to AH15-4 and AH15-06). On completion of logging and sampling, all auger holes were
backfilled in lightly tamped layers using spoil and Type 2.1 gravel mixed with a small amount
cement binder. The auger hole at road surface was compacted using a flat plate fixed to the
end of a crowbar and cleaned as best as possible of any remaining materials before the road
section was again opened to traffic.

Auger hole logs are presented in Appendix A and geotechnical terms and symbols are
presented in Appendix B.

4. 2 Existing Cut Batters
The second activity comprised a walkover inspection and stability assessment of existing
road cuts at locations where road widening is proposed. The majority of proposed widenings
have little or no impact on the existing cut slopes. However there are three locations along
the existing road where re-profiling of cut batters will be required. The major section is from
approximately CH1080 to CH1280 (refer drawing REE-TFR-GT-002), with a shorter section
at the beginning of Top Forestry Road near the junction with Old Ceylon Road (refer drawing
REE-TFR-GT-005) and a short section south of the junction with King Parrot Lane (refer
drawing REE-TFR-GT-004).

The walkover inspection was undertaken by an experienced engineering geologist to assess
the condition and geology of the existing batters. The bedrock exposed in the cuttings was
from the Kin Kin Beds and comprised argillite, phylitte (a low grade metamorphic rock) and
arenite. It exhibited foliated bedding, and was present as low to medium strength rock,
becoming extremely low strength in places due to variable weathering, overlain by
approximately 1 m of residual soil.

The walkover inspection was undertaken on 1 April 2015 and the existing cut sections were
inspected, photographs, and measurements taken of average slope angles and heights. The
inspection photographs are designated Plates 1 to 38, and are divided into three sections to


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