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Geotech Report · OPW26/0094
GEOTECHNICAL REPORT: Proposed Residence
30 Mossman Court
Noosa Heads
DD Sunnyside CD Sunnyside Pty Ltd
November 2023
PG-10899
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Page 2
Ref: PG-10899, 2023-10-16, GR VER 1
Author: Robert Maxwell
7th November, 2023
DD Sunnyside CD Sunnyside Pty Ltd
Email: [email protected]
ATTN: DAVID DODD
Dear Sir,
GEOTECHNICAL INVESTIGATION – PROPOSED RESIDENCE
30 MOSSMAN COURT, NOOSA HEADS
Enclosed is a copy of our report for the above project dated November 2023. An
electronic copy of the report has been issued.
Should you have any queries regarding this report, please do not hesitate to contact
Robert Maxwell or Peter Elkington at this office.
Yours faithfully,
R. MAXWELL (RPEQ 16596)
For and on behalf of
PACIFIC GEOTECH PTY LTD
[email protected]
www.pacgeo.com.au
Page 3
TABLE OF CONTENTS
1.0 INTRODUCTION ................................................................................................... 1
2.0 METHODOLOGY .................................................................................................. 2
3.0 SITE DESCRIPTION................................................................................................ 2
4.0 GEOTECHNICAL MODEL .................................................................................... 4
5.0 GROUNDWATER .................................................................................................. 4
6.0 POTENTIAL GROUND SURFACE MOVEMENTS .................................................. 4
7.0 EARTHWORKS AND SITE PREPARATION CONSIDERATIONS ............................ 5
8.0 BATTERS – SHORT TERM EXCAVATION PROFILE ............................................... 6
9.0 TEMPORARY BATTER SUPPORT ........................................................................... 6
10.0 PERMANENT RETAINING WALLS......................................................................... 7
11.0 BUILDING FOUNDATIONS ................................................................................... 8
12.0 DEWATERING CONSIDERATIONS ...................................................................... 9
13.0 CONSTRUCTON MONITORING ........................................................................ 10
13.1 Monitoring ................................................................................................................ 10
13.2 Preconstruction Survey........................................................................................... 10
14.0 SITE MANAGEMENT .......................................................................................... 10
15.0 LIMITATIONS ...................................................................................................... 11
Appendices
Appendix A
Notes Relating to this Report
Appendix B
Borehole Record Sheets
Appendix C
Site Plan
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Project No. PG-10899 Page | 1
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Ref: PG-10899, 2023-10-16, GR VER 1
DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
1.0 INTRODUCTION
This report contains the results of the geotechnical investigation and provides advice
and recommendations relating to the following:
• Subsurface conditions in accordance with AS 1726
• Foundation recommendations
• Characteristic ground surface movements
• Earthworks considerations
• Batter slope recommendations
• Retention considerations
• Retaining wall design parameters
• Construction Considerations
Proposed Development
It is understood that the proposed development is to comprise of the construction of
a two-storey residence above a single level basement at 30 Mossman Court, Noosa
Heads. Earthworks are envisaged to consist of cuts of up to 3m for the basement.
The proposed development is indicated below.
PROPOSED DEVELOPMENT
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Project No. PG-10899 Page | 2
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Ref: PG-10899, 2023-10-16, GR VER 1
DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
2.0 METHODOLOGY
The geotechnical investigation comprised the drilling and sampling of one (1)
borehole to a depth of 9.0m, using a Compac 018 drilling rig fitted with 100mm solid
flight augers, and one (1) hand auger across the proposed building area. Dynamic
Cone Penetrometer (DCP) testing was conducted adjacent to the boreholes.
The soil classification descriptions and field tests were carried out in general
accordance with Australian Standards.
AS 1726 Geotechnical Site Investigations
AS 1289 Methods of Testing Soils for Engineering Purposes
Borehole records, Dynamic Cone Penetrometer test results and a site plan showing
the test locations are appended to the report.
3.0 SITE DESCRIPTION
The site of the proposed development is located at 30 Mossman Court, Noosa
Heads. The site was bordered by Mossman Court to the south, existing residences to
the east and west, and a canal to the north.
At the time of the investigation, the site was occupied by an existing two storey
residence and detach single garage. The site was relatively level and drainage was
considered poor to fair.
Refer following aerial and site photographs for typical site conditions.
AERIAL IMAGE
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DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
SITE PHOTOGRAPHS
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DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
4.0 GEOTECHNICAL MODEL
The subsurface profile encountered in borehole BH01 generally consisted of a
surficial concrete layer associated with the driveway, overlying very loose to loose
sand fill to a depth of 2.3m, overlying natural sands that were generally medium
dense to dense, becoming indurated at a depth of 6.6m, and continued to the
termination of borehole BH01 of 9.0m.
In HA02, loose silty sand fill was encountered to a depth of 0.6m, overlying loose
sand fill to the termination depth of 1.0m.
Table 1 presents a summary of the encountered subsurface profile. Detailed
borehole record sheets are appended to this report.
TABLE 1 SUBSURFACE PROFILE SUMMARY
NATURAL
SAND
BH No. FILL BH TD
Dense to Very Dense
Medium Dense to Dense
(Indurated)
BH01 0.0-2.3 2.3-6.6 6.6-TD 9.0
BH02 0.0-TD NE NE 1.0
Notes:
1. All depths in metres below ground level at time of investigation.
2. NE - Not Encountered; TD - Termination Depth.
5.0 GROUNDWATER
Groundwater was noted in borehole BH01 at a depth of 2.8m at the time of drilling.
Water levels can be expected to similar to the tidal levels of the neighbouring canal
and may vary with seasonal and climatic conditions.
Typically the groundwater levels in the area are encountered at levels of
approximately RL 0.5m to RL 1.0m. Fluctuations of +/- 0.5m are typically noted in the
area.
Increases in the groundwater levels often occur following significant rainfall events
(floods) with the groundwater levels to as much as RL 1.5m to RL 2.0m being noted in
the area.
6.0 POTENTIAL GROUND SURFACE MOVEMENTS
On the basis of the field testing results, and the depth of fill encountered, the site
must be classified Class P, in accordance with AS 2870-2011, by definition. This does
not necessarily mean the site is a problem, just that it is excluded from other
classifications.
From a reactivity perspective, the investigation and laboratory test results indicate
that the development site would be classified Class ‘S’, slightly reactive, in
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Ref: PG-10899, 2023-10-16, GR VER 1
DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
accordance with AS 2870-2011 'Residential Slabs and Footings', following
appropriate ground improvement works under the footings.
It is recommended that the readers satisfy themselves that the use of AS 2870-2011 is
applicable for the proposed design and the above site classification re-confirmed
following the completion of the bulk earthworks operation.
7.0 EARTHWORKS AND SITE PREPARATION CONSIDERATIONS
Earthworks are expected to comprise cuts of up to 3m for the proposed basement
excavation. Some over-excavation may be required to allow for ground
improvement works.
It is recommended that the following site preparation and earthworks procedures be
carried out as part of the earthworks procedures during development.
• All earthworks operations should be carried out in general accordance with
AS 3798-2007 "Guidelines on Earthworks for Commercial and Residential
Developments".
• Trafficability across the site at the time of the investigation was assessed to be
fair to good with no difficulties encountered at the time of the investigation.
Following stripping and excavation for the basement, the exposed sands will
be difficult to traffic for conventional vehicles. Consideration could be given
to adopting a 150mm layer of pavement gravel as a working platform across
the site.
• All topsoil (i.e. soil containing organic matter) and soils containing deleterious
matter should be stripped from the construction area at the commencement
of the earthworks operation. Dirty sands (i.e. >5% fine content), particularly
the upper level sands (existing fill), could be difficult to manage and
consideration could be given to the disposal of this material.
• The stripped surface should be proof rolled using a vibrating roller or a large
vibrating plate compactor (say 300kg), to identify areas of weak surficial soils
and to compact the upper level material.
• The “clean” sands on site will be suitable for re-use as structural fill, provided
material is free of organic matter and deleterious material. The silty sand may
prove difficult to re-use and consideration should be given to preferential
disposal of this material.
• Imported fill should be of fair to good quality with a minimum Soaked CBR
value of 10%, a maximum Iss=1.0% and a maximum particle size of 75mm, or a
clean sand.
• All filling should be undertaken in layer thicknesses of approximately 250mm
(or as appropriate for the compaction equipment being used). Fill should be
compacted to a minimum dry density ratio of 98% Standard in accordance
with AS1289 5.1.1 for cohesive fill and 75% Density Index for non-cohesive fill
(i.e. sand).
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DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
• Field density testing should be carried out to check the standard of
compaction achieved and the placement moisture content. The frequency
and extent of testing should be as per guidelines in AS.3798-2007.
8.0 BATTERS – SHORT TERM EXCAVATION PROFILE
It is understood that cut batters to 3m in height will be required as part of the
basement construction.
Considering the proposed maximum height of cut, the following recommendations
are made for the bulk excavation of the site.
Batters < 2.0m in height
• 1V:1.5H batter with crest of batter >2m from buildings or structures.
Batters > 2.0m in height
• 1V:1.5H batter with the crest of the batter at least 2.0m inside the site
boundary.
• 2.0m minimum distance from any building or structure.
If batters are to be left exposed for an extended period of time, a battler angle of
1V:2H is recommended and berm widths are to be strictly maintained. The above
batter slopes assume no seepage is present in the batters and the batters are above
the water table.
9.0 TEMPORARY BATTER SUPPORT
Where the excavations cannot be battered to a stable angle, they will need to be
supported to prevent instability. Support systems could include:
• Sheet Piles – anchoring or cross-bracing of the excavation are likely to be
required for sheet piles or possibly cantilevered, and due consideration should
be given to the potential for anchor installation and vibration to adversely
affect adjacent areas.
• Contiguous Piles – whilst no vibration is associated with their installation, it is
likely a more expensive solution.
• Steel Soldier Piles and Jetted Precast Panels – difficulties in maintaining
stability whilst jetting the panels and is likely to be a higher risk option.
Where sheet piles are to installed through medium dense or ‘denser’ sands, pre-
drilling may be required to ensure installation.
Where sands are retained, shoring pressures should be based on the lateral earth
pressure coefficients given in Table 2, in conjunction with a triangular pressure
distribution where the pressure can be calculated from P=0.5ka H2, provided the
excavation is not surcharged by adjacent buildings/services and some tolerance or
movement exists.
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DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
TABLE 2 LATERAL EARTH PRESSURE COEFFICIENTS
Lateral Earth Pressure Coefficients
Unit Weight
Material Strength (K)
(t/m3)
Flexible Propped
Very loose to loose 1.8 0.40 0.60
Sands Medium dense 2.0 0.30 0.50
Dense to very dense 2.1 0.25 0.45
Pressures for unsurcharged propped walls could be designed based on a uniform
pressure distribution with depth, where the pressure P = 0.65ka H (kPa) where H is
the depth of the excavation. The shoring wall should also be checked for a
triangular distribution calculated using the lateral earth pressure coefficients present
in Table 2 for a propped wall.
The temporary support system should also take into consideration the possible needs
to over-excavate the basement for ground improvement works.
It should be noted that lateral deflection of the retention system will occur,
irrespective of the retention system adopted. In additional to lateral movements,
vertical movement of the soils behind the retention system will result. The effects of
the vertical and horizontal movements may be seen at a distance equal to 2 or 3
times the height of the excavation.
Subject to detailed design, movements as much as 1% to 2% of the depth of the
excavation could occur behind a cantilevered pile wall.
10.0 PERMANENT RETAINING WALLS
Basement walls should be designed using a pressure coefficient for the at rest case
of K0 = 0.5.
Unit wall force P is given by:-
P = 0.5 K0 H12 (kN/m run of wall)
Passive resistance at the base of the wall can be calculated from:-
P = 0.5 Kp Hw2
where Kp = 3.25 (ignores wall friction effects) for medium dense sands
Hw = front face of wall contributing to passive resistance (m)
For the sliding resistance calculation, the angle of friction for sand () compacted to
not less than 75% density index can be taken as 32° for walls with a key. For walls
2
without a key, the angle of friction for sliding resistance should be taken as 3 or 21°.
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Project No. PG-10899 Page | 8
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Ref: PG-10899, 2023-10-16, GR VER 1
DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
11.0 BUILDING FOUNDATIONS
Given the encountered subsurface profile, a high level footing system would
generally be suitable for the support of the proposed structure, with appropriate
ground improvement works and due consideration of the potential hydrostatic uplift
forces.
Assuming an excavation depth of 3m for the basement, provided the founding soils
are compacted to a minimum Density Index of 75% for a minimum depth of 750mm
below the footings, an allowable bearing capacity of 200kPa could be adopted for
the foundation design.
This classification could possibly be achieved through insitu compaction of the
exposed sands but may require the over-excavation of the founding soils (up to
400mm), compaction of the exposed material and the replacement of the
excavation using “clean” sand.
It should be noted that silty sands were encountered in the sand profile and filling
should be preferably disposed of. Some difficulties in treating these sands should be
expected.
It is strongly recommended that if a high level footing system is to be adopted,
sufficient “clean” sand from higher in the excavation profile be stockpiled on-site, to
allow for the replacement of the silty sands at the founding level.
To enable the required ground improvement works to be undertaken, the following
earthworks operation is recommended:
i. Install the temporary retention system and dewatering system.
ii. Dewater the site to at least 0.9m below the final excavation level.
iii. Excavate the site to the design basement level and test the base of the
excavation to determine the extent of over-excavation required.
iv. Following determination of the required extent of over-excavation, excavate
the site to the required level and compact the exposed sands using a large
(300kg plus) vibrating plate compactor or a small smooth drum roller. It
should be noted that the silty sands encountered at some test locations could
be difficult to compact and manage, if not appropriately dewatered. It may
be necessary to remove the silty sands and replace them with clean sands
from higher in the excavation profile.
v. Replace the over-excavation with “clean” sand and compact in layers to the
design founding level. The founding soils should be compacted to a
minimum Density Index of 75% (in accordance with AS 1289 5.6.1).
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Project No. PG-10899 Page | 9 November 2023 Ref: PG-10899, 2023-10-16, GR VER 1 DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads Foundation Design Parameters For footings founded 3m below the ground level, an allowable bearing capacity of 200kPa could be adopted, following confirmation that a minimum Density Index of 75% is present for a minimum depth of 750mm below the footings. If the exposed sands are disturbed or loosened during the excavation operation, they should be recompacted. Consideration should be given to placing a 50mm thick (minimum) concrete binding layer across the footings, immediately following excavation. Settlement Potential Settlements from underlying improved sands and natural soils beneath a pad footing of 2.5m width (i.e. maximum column load of 1500kN) at a nominal founding depth of 3.0m below existing ground level at a design bearing pressure of 200kPa have been calculated to be in the order of 15mm with anticipated differential settlements of between 25% and 50% of the calculated total settlement for pad footings founded at a similar depth. The settlement will occur as “immediate” settlement as the building loads are applied. Hydrostatic Uplift Forces For a fully tanked basement, hydrostatic uplift forces should be considered in the design. It is recommended hydrostatic uplift forces in groundwater levels to at least RL1.5 to 2.0m be taken into consideration on this site and checked for the Q100 flood condition. 12.0 DEWATERING CONSIDERATIONS Construction of the basement and foundation system will likely require dewatering. The groundwater will need to be lowered to a minimum of 0.9m below the final excavation depths, to allow the compaction of the founding soils to be achieved. Groundwater levels are expected to be similar to the tidal levels in the neighbouring canal. The HAT for Noosa Heads (Noosa River) is expected to be in the order of RL 1.07m and approximately 1.6m below ground level at the site. As the proposed excavation of up to 3m plus an additional 0.9m for ground improvements, where required, a drawdown of approximately 2 to 2.5m is therefore expected to be required. Dewatering is typically achieved through the use of perimeter spears and internal wells. Settlements inducted by 2m of drawdown (i.e. 20kPa effective stress increase) are estimated to result in settlements of less than 5mm. Therefore, it is considered that the effects of dewatering on the adjoining structures will be minimal.
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Ref: PG-10899, 2023-10-16, GR VER 1
DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
13.0 CONSTRUCTON MONITORING
Construction vibrations could potentially cause settlement in the loose upper level
sands, thereby damaging nearby structures founded in these strata. Prior to
commencement of construction on site, it is recommended that a detailed
dilapidation survey be undertaken to establish the condition of all existing adjacent
structures.
13.1 Monitoring
It is recommended that monitoring points should be established on the retention
system to check for deflections during excavation. A suggested spacing of the
monitoring points would be 10m along the walls. A regular monitoring program of
these stations should be implemented.
Monitoring must commence before any excavation to establish baseline readings.
13.2 Preconstruction Survey
Prior to commencement of construction on site, it is recommended that a
dilapidation survey be undertaken on the adjacent structures.
This survey should include the following:
• The extent of exiting damage (if any)
• The general condition of the property, ie. Condition of all exposed columns
and beams, partition walls and cladding etc.
• Road, kerb and channel and footpath condition adjacent development site.
14.0 SITE MANAGEMENT
To maintain the long term performance of the structure, good management of the
soil conditions and the development is vital throughout the life of the development.
The following are some specific comments with respect to site management:
• The ground surface around the perimeter of the buildings should slope away
from the structure and fall to the stormwater system. Water should not be
allowed to pond adjacent to the buildings.
• Founding soils should not be allowed to become saturated.
• Service trenches under the buildings should be kept to a minimum. Saturation
of the on-site material will result in an increase in settlement potential.
• Footings should be poured immediately after compaction. If footings cannot
be poured on the same day as compaction, a blinding layer of at least
50mm thickness is recommended.
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DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
• Trees, garden beds and other vegetation should be planted at a distance at
least equivalent to three quarters of their mature height away from the
structures. This will assist in minimising shrinkage movements in the expansive
on-soils.
15.0 LIMITATIONS
We have prepared this report for the Proposed Residence at 30 Mossman Court,
Noosa Heads. The report is provided for the exclusive use of DD Sunnyside CD
Sunnyside Pty Ltd, for this project only and for the purposes outlined in the report. It
should not be used by, or relied upon, for other projects on the same or different sites
or by a third party. In preparing this report, we have relied upon information
provided by the client or their agents.
The results are indicative of the subsurface conditions on site only at the specific
testing locations. Subsurface conditions can change between test locations and
the design and construction should take the spacing of the testing and testing
methods adopted and the potential for variation between the test locations.
It is recommended that Pacific Geotech be engaged to provide advice and ensure
the development is undertaken in accordance with the assumptions made in writing
this report.
This is not to reduce the level of responsibility accepted by Pacific Geotech, but
rather to ensure that the parties who may rely on the information contained in this
report are aware of the responsibilities they assume in doing so.
Yours faithfully,
R. MAXWELL (RPEQ 16596)
For and on behalf of
PACIFIC GEOTECH PTY LTD
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Project No. PG-10899
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Ref: PG-10899, 2023-10-16, GR VER 1
DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
APPENDICES
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Project No. PG-10899
November 2023
Ref: PG-10899, 2023-10-16, GR VER 1
DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
APPENDIX A
NOTES RELATING TO THIS REPORT
Page 17
Notes Relating to this Report
Reports other particles present (e.g. sandy clay) as set
out below:
The report has been prepared by qualified
personnel, is based on the information Soil
Particle Size
obtained from field and laboratory testing, and Classification
has been undertaken to current engineering Clay less than 0.002mm
standards of interpretation and analysis. Silty 0.002 to 0.06mm
Sand 0.06 to 2mm
Gravel 2 to 60mm
Every care has been taken with the report as it
relates to interpretation of subsurface
Non-cohesive soils are classified on the basis of
conditions, discussion of geotechnical
relative density which can be correlated from
conditions and contains recommendations or
the results of Standard Penetration Test (SPT) as
suggestions for design and construction.
below:
However, unexpected variations in ground
conditions will occur. The potential for this will
SPT ‘N’ Value
depend partly on testing, spacing and Relative Density
(blows/300mm)
sampling frequency. Very Loose less than 4
Loose 4 – 10
If variations are identified, Pacific Geotech Medium Dense 10 – 30
would be pleased to assist with additional Dense 30 – 50
investigations or advice to resolve the matter. Very Dense greater than 50
Copyright Cohesive soils are classified on the basis of
strength (consistency) and can be quantified
This report is the property of Pacific Geotech by the Pocket Penetrometer test, Vane Shear
Pty Ltd. The report may only be used for the test, laboratory testing or engineering
purpose for which it was commissioned and in examination. The strength terms are defined as
accordance with the Terms of Engagement of follows:
proposal. Unauthorised use of this report is
prohibited. Unconfined Compressive
Classification
Strength kPa
Borehole and Test Pit Logs Very Soft less than 25
Soft 25 - 50
The borehole and test pit logs presented in this Firm 50 – 100
report are an engineering and/or geological Stiff 100 – 200
interpretation of the subsurface conditions, and Very Stiff 200 - 400
Hard greater than 400
their reliability will depend to some extent on
Friable strength not attainable – soil
frequency of sampling and the method of crumbles
drilling or excavation.
Rock types are classified by their geological
Interpretation of the information and its
names, together with descriptive terms
application to design and construction should
regarding weathering, strength, defects, etc.
therefore take into account the spacing of
boreholes or pits, the frequency of sampling, Planarity
and the possibility of other than ‘straight line’ CU Curved
variations between the test locations. DIS Discontinuous
IR Irregular
Description and Classification Methods PR Planar
ST Stepped
The description and classification of soils and UN Undulose
rocks used in this report are based on AS 1726.
Soil types are described according to the
predominating particle size and behaviour as
set out in the attached Unified Soil
Classification Table qualified by the percent of
October 2017 pg. 1
Page 18
Roughness Investigation Methods
POL Polished
RJ Rough Test Pits: These are typically undertaken with a
S Smooth backhoe or a tracked excavator, allowing
SL Slickened examination of the insitu soils. Limitations of test
VR Very Rough
pits are the problems associated with collapse
of the pits, disturbance and difficulty of
Defects Type reinstatement and the consequent effects on
BP Bedding Parting close-by structures. Care must be taken if
CL Cleavage construction is to be carried out near test pit
CO Contact locations to either properly recompact the
CS Crushed Seam backfill during construction or to design and
CZ Crushed Zone
construct the structure so as not to be
DB Drilling Break
adversely affected by poorly compacted
DK Dyke
DL Drill Lift backfill at the test pit location.
DZ Decomposed Zone
FC Fracture Hand Auger Drilling: A borehole of typical
FL Foliation diameter of between 50mm to 75mm advance
FZ Fracture Zone manually operated equipment. Premature
HB Handling Break refusal of the hand augers can occur on a
IS Infilled Seam variety of materials such as fill, gravel, hard
JT Joint clays and collapse of the borehole (typically in
H Schistosity non-cohesive soil).
SI Sill
SM Seam Continuous Spiral flight Augers: The borehole is
SS Shear Seam advanced using 65mm to 100mm diameter
SZ Shear Zone
continuous spiral flight augers, which are
VN Vein
withdrawn at intervals to allow sampling and
VO Void
insitu testing. Augers of up to 300mm in
Sampling diameter are used to recover larger volumes of
sample. Samples are returned to the surface
Sampling is undertaken during the fieldwork to by the flights or may be collected after
allow examination of the soil or rock and to withdrawal of the auger flights. Samples can
allow laboratory testing to be undertaken. be disturbed and layers may become mixed.
Augering below the groundwater table can be
Disturbed samples taken during drilling provide less reliable than augering above the water
information on plasticity, grain size, colour, table.
moisture content and minor constituents. Bulk
samples are similar but of greater volume A Tungsten Carbide (TC) bit for auger drilling
required for some test procedures such as CBR into rock can be used to indicate rock strength
testing. and continuity by variation in drilling resistance
and from examination of recovered rock
Undisturbed samples are taken by pushing a fragments but provides only an indication of
thin-walled sample tube, usually 50mm the likely rock strength. Where rock strengths
diameter (known as a U50), into the soil and may have a significant impact on construction
collecting a sample of the soil contained in a feasibility or costs, then further investigation by
relatively undisturbed state. Such samples yield means of cored boreholes may be warranted.
information on structure and strength, and are
necessary for laboratory determination of shear Wash Boring: The borehole is advanced by a
strength and compressibility. Undisturbed bit attached to the end of a hollow rod string,
sampling is generally effective only in cohesive with water being pumped down the drill rods
soils. and returned up the annulus of the borehole,
carrying the drill cuttings. Changes in
Details of the type and method of sampling stratification can be determined from the
used are given on the attached logs. return, together with information from “feel”
and rate of penetration.
Page 19
The borehole can be stabilised through the use using a Cone Penetrometer in general
of drilling mud as a circulating fluid. The term accordance with AS 1289 6.5.1, 1999.
‘mud’ encompasses a range of products
ranging from bentonite to polymers such as In the tests, a 36mm diameter rod with a
Revert or Biogel. conical tip is pushed continuously into the soil,
the reaction being provided by a hydraulic
Continuous Core Drilling: A continuous core ram system. Measurements are made of the
sample is obtained using a diamond tipped end bearing resistance on the cone and the
core barrel. This technique provides a reliable fractional resistance on a separate 135mm
(but relatively expensive) method of long sleeve, immediately behind the cone.
investigation. In rocks, an NMLC triple tube Pore Pressure is recovered through a pore ring
core barrel is used, which gives a core of about located either within, or more usually
50mm diameter. The length of core recovered immediately behind the cone/tip.
is compared to the length drilled and any
length not recovered is shown as CORE LOSS. As penetration occurs (at a rate of
approximately 20mm per second) and data is
Standard Penetration Tests: Standard recorded every 20mm of penetration, the
Penetration Tests (SPT) are used mainly in non- results are presented graphically.
cohesive soils, but can also be used in cohesive
soils as a means of indicating density or The information provided on the plot
strength and also of obtaining a disturbed comprises:
sample. The test procedure is described in
Cone resistance – expressed in mPa
Australian Standard 1289, “Methods of Testing
Sleeve friction – expressed in kPa
Soils for Engineering Purposed”, Test 6.3.1.
Friction ratio – the ratio of sleeve
The test is carried out in a borehole by driving a friction to cone resistance expressed as
50mm diameter split sample tube with a a percentage.
tapered shoe, under the impact of a 63kg Pore pressure in kPa
hammer, with a free fall of 760mm. The sample Tilt of probe (in degrees).
is driven in three successive 150mm increments
and the ‘N’ value is taken as the number of
The ratios of the sleeve resistance to cone
blows for the last 300mm. In dense soils, hard
resistance will vary with the type of soil
clays or weak rock, the full 450mm penetration
encountered, with higher relative friction in
may not be practicable and the test is
clays than in sands. Friction ratios of 1% to 2%
discontinued.
are commonly encountered in sands and rising
The test results are reported in the following to 2% to as high as 8%, and higher in organic
form: soils. Soil descriptions based on cone
resistance and friction ratios are only inferred
In the case where full penetration is and must not be considered as exact.
obtained with successive blow counts
for each 150mm of , say, 4, 6 and 7 Stratification can be inferred from the cone
blows, as and friction traces and from experience and
N = 13 information from nearby boreholes, etc. Where
4, 6, 7 shown, this information is presented for general
In a case where the test is discontinued guidance, but must be regarded as
short of full penetration, say after 15 interpretive.
blows for the first 150mm and 30 blows
Dynamic Cone Penetrometers:
for the next 40mm, as
N > 30
Dynamic Cone Penetrometer (DCP) tests are
15, 30/40mm
carried out by driving a 16mm diameter rod
into the ground with a 9kg sliding hammer
Cone Penetrometer Testing (CPT): Cone
dropping 510mm and counting the blows for
Penetrometer Testing with or without pore
successive 100mm increments of penetration.
pressure measurement (CPTu) is carried out
Page 20
Logs for fill, it may be difficult to reliably determine
the extent of the fill.
The borehole or test pit logs are an
interpretation of the subsurface conditions, and Laboratory Testing
their reliability will depend to some extent on
the frequency of sampling and the method of Laboratory testing is carried out in general
drilling or excavation. accordance with Australian Standard 1289
‘Methods of Testing Soil for Engineering
Interpretation of the information shown on the Purposes’.
logs, and its application to design and
construction, should therefore take into Site Anomalies
account the spacing of the boreholes or test
In the event that conditions encountered on
pits, the method of drilling or excavation, the
site during construction appear to vary from
frequency of sampling and testing and the
those which were expected from the
possibility of other than “straight line” variations
information contained in the report, the
between the boreholes or test pits. Subsurface
company requests that it immediately be
conditions between boreholes or test pits may
notified. Most problems are much more readily
vary significantly from conditions encountered
resolved when conditions are exposed than at
at the borehole or test pit locations.
some later stage.
Groundwater
Review of Design
Where groundwater levels are measured in
Where major civil or structural developments
boreholes, there are several potential
are proposed or where only a limited
problems:
investigation has been completed or where the
Although groundwater may be geotechnical conditions/constraints are quite
present, in low permeability soils it may complex, it is prudent to have a design review.
enter the hole slowly or perhaps not at
Site Inspection
all during the time it is left open.
A localised perched water table may
Pacific Geotech would be pleased to provide
lead to an erroneous indication of the
engineering inspection services for
true water table.
geotechnical aspects of work to which this
Water table levels will vary from time to
report is related:
time with seasons or recent weather
changes and may not be the same at Requirements could range from:
the time of construction.
The use of water or mud as a drilling i. a site visit to confirm that conditions
fluid will mask any groundwater inflow. exposed are no worse than those
Water has to be flushed from the hole interpreted, to
and drilling mud must be washed out ii. a visit to assist the contractor or other
of the hole or ‘reverted’ chemically if site personnel in identifying various
water observations are to be made. soil/rock types such as appropriate
More reliable measurements can be made by footing or pier founding depths, or
installing standpipes from which ongoing iii. full time engineering present on site.
monitoring can be undertaken.
Fill
The present of fill materials can often be
determined only by the inclusion of foreign
objects (e.g. bricks, steel ,etc.) or by distinctly
unusual colour, texture or fabric. Identification
of the extent of fill materials will also depend on
investigation methods and frequency. Where
natural soils similar to those at the site are used
Page 21
Project No. PG-10899
November 2023
Ref: PG-10899, 2023-10-16, GR VER 1
DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
APPENDIX B
BOREHOLE RECORD SHEETS
Page 22
Borehole No.
BH01
Page 1 of 2
Project No.: PG-10899
Client: DD Sunnyside CD Sunnyside Pty Ltd Commenced: 06/10/2023
Project Name: Proposed Residence Logged By: RR
Hole Location: 30 Mossman Court, Noosa Heads Checked By:
Hole Position:
Drill Model and Mounting: Compac 018 RL Surface: No survey
Hole Diameter: Datum: AHD Operator: RR
Drilling Information Soil Description DCP
Classification
Graphic Log
Samples Material Description
Recovery
Tests Fraction, Colour, Structure, Bedding,
Symbol
Method
Casing
Remarks Plasticity, Sensitivity, Additional
Water
RL Depth
(m) (m) 0 5 10 15 20 25
Concrete (CCT)
0.15
SP FILL SAND (SP) Very loose to loose, fine to medium grained, pale
yellow brown, moist.
ASS 0.50-1.00 m
1
ASS 1.00-1.50 m
D 1.10-1.50 m
ASS 1.50-2.00 m
ER PACGEO 1.01.2 LIB.GLB Log PACGEO BOREHOLE PG-10899.GPJ <<DrawingFile>> 17/10/2023 10:45 10.03.00.09 Datgel Lab and In Situ Tool - DGD | Lib: pacgeo 1.01.2 2022-05-25 Prj: Precise 1.01 2016-11-23
2
ASS 2.00-2.50 m
2.30
SP NATURAL SAND (SP) Medium dense, fine to medium grained, pale
yellow brown, moist.
AD/T
ASS 2.50-3.00 m
D 2.60-3.00 m
2.80
SP SAND (SP) Medium dense to dense, fine to medium grained, pale grey,
wet.
3
ASS 3.00-3.50 m
ASS 3.50-4.00 m
4
4.10
D 4.10-4.50 m SP SAND (SP) Medium dense, fine to medium grained, pale grey, wet.
Method Water Samples and Tests Remarks
AS - Auger Level (Date) U - Undisturbed Sample
RR - Rock Roller D - Disturbed Sample 1. Groundwater encountered at 2.80m.
WB- Washbore Inflow SPT - Standard Penetration Test 2. DCP refusal at 3.07m.
B - Bulk Sample 3. Standpipe installed to 3.15m.
Classification Symbols and
Support Soil Descriptions
C - Casing
Based on Unified Soil
Classification System
Page 23
Borehole No.
BH01
Page 2 of 2
Project No.: PG-10899
Client: DD Sunnyside CD Sunnyside Pty Ltd Commenced: 06/10/2023
Project Name: Proposed Residence Logged By: RR
Hole Location: 30 Mossman Court, Noosa Heads Checked By:
Hole Position:
Drill Model and Mounting: Compac 018 RL Surface: No survey
Hole Diameter: Datum: AHD Operator: RR
Drilling Information Soil Description DCP
Classification
Graphic Log
Samples Material Description
Recovery
Tests Fraction, Colour, Structure, Bedding,
Symbol
Method
Casing
Remarks Plasticity, Sensitivity, Additional
Water
RL Depth
(m) (m) 0 5 10 15 20 25
SP SAND (SP) Medium dense, fine to medium grained, pale grey, wet.
(continued)
6
6.60
ER PACGEO 1.01.2 LIB.GLB Log PACGEO BOREHOLE PG-10899.GPJ <<DrawingFile>> 17/10/2023 10:45 10.03.00.09 Datgel Lab and In Situ Tool - DGD | Lib: pacgeo 1.01.2 2022-05-25 Prj: Precise 1.01 2016-11-23
SM Silty SAND (SM) Dense to very dense, fine to medium grained, dark
brown, wet (indurated sand).
AD/T
7
8
D 8.60-9.00 m
9.00
9
Hole Terminated at 9.00 m
Method Water Samples and Tests Remarks
AS - Auger Level (Date) U - Undisturbed Sample
RR - Rock Roller D - Disturbed Sample 1. Groundwater encountered at 2.80m.
WB- Washbore Inflow SPT - Standard Penetration Test 2. DCP refusal at 3.07m.
B - Bulk Sample 3. Standpipe installed to 3.15m.
Classification Symbols and
Support Soil Descriptions
C - Casing
Based on Unified Soil
Classification System
Page 24
Borehole No.
HA02
Page 1 of 1
Project No.: PG-10899
Client: DD Sunnyside CD Sunnyside Pty Ltd Commenced: 06/10/2023
Project Name: Proposed Residence Logged By: RR
Hole Location: 30 Mossman Court, Noosa Heads Checked By:
Hole Position:
Drill Model and Mounting: Hand Auger RL Surface: No survey
Hole Diameter: Datum: AHD Operator: RR
Drilling Information Soil Description DCP
Classification
Graphic Log
Samples Material Description
Recovery
Tests Fraction, Colour, Structure, Bedding,
Symbol
Method
Casing
Remarks Plasticity, Sensitivity, Additional
Water
RL Depth
(m) (m) 0 5 10 15 20 25
SM FILL Silty SAND (SM) Loose, fine to medium grained, dark brown, with
fine sized gravel, dry.
HA
0.60
SP FILL SAND (SP) Loose, fine to medium grained, pale yellow brown,
moist to dry.
1.00
1
Hole Terminated at 1.00 m
ER PACGEO 1.01.2 LIB.GLB Log PACGEO BOREHOLE PG-10899.GPJ <<DrawingFile>> 17/10/2023 10:45 10.03.00.09 Datgel Lab and In Situ Tool - DGD | Lib: pacgeo 1.01.2 2022-05-25 Prj: Precise 1.01 2016-11-23
2
3
4
Method Water Samples and Tests Remarks
AS - Auger Level (Date) U - Undisturbed Sample
RR - Rock Roller D - Disturbed Sample 1. Groundwater not encountered.
WB- Washbore Inflow SPT - Standard Penetration Test 2. DCP refusal at 2.38m.
B - Bulk Sample
Classification Symbols and
Support Soil Descriptions
C - Casing
Based on Unified Soil
Classification System
Page 25
Project No. PG-10899
November 2023
Ref: PG-10899, 2023-10-16, GR VER 1
DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads
APPENDIX C
SITE PLAN
Page 26
HA02
BH01
Drawn
Project: Proposed Residence
RM
Drawing No.
Date
Location: 30 Mossman Court, Noosa Heads A4
Oct 23
PG-10899-01
Checked
Client: DD Sunnyside CD Sunnyside Pty Ltd
Used in these records
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