Original source · versioned page text
271117 Techtonic GeoTech Cooroy Mtn Rd
Attached to the e-mail TPA21/0010 - Soil test report.
27 November 2017 Project No. 17385-001-Rev0 Mr Ken Freeman Email: [email protected] Copy to: Teresa Hutton ([email protected]) GEOTECHNICAL INVESTIGATION AND SLOPE STABILITY ASSESSMENT PROPOSED EXTENSION TO RESIDENCE 400 COOROY MOUNTAIN ROAD, COOROY Dear Ken, 1.0 INTRODUCTION As requested, Tectonic has undertaken a geotechnical investigation and slope stability assessment for proposed extensions to the residence at 400 Cooroy Mountain Road, Cooroy. This report presents the results of our investigation and slope stability assessment, together with geotechnical advice for the development, including earthworks, footings, retaining walls, and drainage. In summary, subject to implementation of the recommendations made herein, it is assessed that there is a Low Risk of slope instability affecting the residence in accordance with the Australian Geomechanics Society “Guidelines for Landslide Risk Management”, dated March 2007 (AGS 2007). 1.1 Details of the Site and Proposed Development The site is described as Lot 11 on SP148816 and covers an area of 195, 512 m² (refer to Text Figure 1 on the following page). Access to the property from Cooroy Mountain Road is via a shared driveway located along the western property boundary. The existing residence is located in the south-western corner of the lot, and consists of a two storey house, with a separate garage and small office building to the east. A two-tiered rock boulder retaining wall is located upslope (south) of the house and driveway. The surrounding land-use is predominantly pastoral, with some densely vegetated bushland on Mount Cooroy to the south. Further details regarding the site are provided in Section 3. Tectonic Geotechnical Pty Ltd PO Box 899, Buderim, QLD 4556 Mobile 0437 755 750 / 0437 756 711 www.tectonicgeo.com.au A.B.N. 83 165 727 828
See the original
The page text is free to read. Viewing or downloading an original file needs an account.
Log in to see the originalLog in to download the original file
Large file: the download may take up to a minute.
Searchable page text hides email addresses. Original files are unchanged and may show email addresses.
Full text of the other 28 pages
Page 2
Mr Ken Freeman 17385-001-Rev0
27 November 2017
Lot boundary
Existing house
Text Figure 1: Aerial image of area from 2016 (courtesy Noosa Shire Council Interactive maps website)
Based on our review of the proposed development concept plan , email correspondence from JTC
Engineers (the civil/structural engineers for the project), and from conversations with the client on site, it is
understood that the proposed work will include the construction of a porte cochere near the entrance to the
house, a carport to the west of the house, and an extension to the existing garage.
A possible two-storey extension is also being considered on the eastern side of the existing house,
comprising additional rooms, a cantilevered pool, and rooftop garden. We have been advised by JTC that
this is to be constructed using suspended floor slabs, and reinforced core filled blockwork. Cut and fill
earthworks will be required to construct a building platform.
Earthworks comprising placement of about 2 m of fill above existing ground level will also be undertaken
on the northern side of the house to create a levelled area for a golf putting green. The fill embankment will
be retained by terraced retaining walls having a maximum overall height of 2 m. The existing swimming
pool located in this area is proposed to be infilled, with no demolition of the pool shell currently proposed.
1.2 Method and Scope of Investigation
As part of our slope stability assessment, a desk-top study was carried out comprising a review of
published geological maps, publicly available site information and a ‘soil test’ report prepared by Bowler
Geotechnical (Sunshine Coast) Pty Ltd (Bowler) for the original construction of the house (Bowler Job No
4095, dated 30 August 2004).
A walk-over survey was conducted in order to make an appraisal of the site conditions in regard to
topography, drainage, vegetation cover, geology, erosion, condition of any existing structures, and to look
for surface indicators of existing slope instability. The walk-over survey was carried out by an
experienced engineering geologist from Tectonic on 9 November 2017. The results of the desk top study
and site walkover are summarized in Section 3 below.
Tectonic also undertook a subsurface investigation in the proposed development areas, comprising the
excavation of six test pits using a six tonne excavator that was supplied by the client. The test pits were
excavated to depths of between 1.2 m and 2.8 m below ground level (BGL), and the majority were
terminated where bucket refusal was reached on rock. Pocket penetrometer testing was undertaken in
test pit sidewalls and on excavated undisturbed blocks of cohesive soil to help assess soil
strength/consistency. Rock strength was qualitatively assessed by observation of excavation
characteristics and using a geologists pick. The local geology and subsurface conditions are discussed
2/13
Page 3
Mr Ken Freeman 17385-001-Rev0
27 November 2017
in Sections 3.1 and 3.2, with test pit reports attached at the end of this report. Test locations are shown
on Figure 1 – Site Plan, which is also attached.
Disturbed samples were recovered from the test pits. One sample was forwarded to a NATA accredited soil
laboratory for percent fines and Atterberg Limits testing to help with material classification and assessment of
material properties. The results of laboratory testing are summarised in Section 2.0 and the laboratory test
report is attached to this letter.
1.3 Qualifications of Responsible Engineer
This letter report has been reviewed by Mr Scott Davis, an RPEQ experienced in undertaking slope
stability assessments.
2.0 LABORATORY TESTING RESULTS
One soil sample from test pit TP3 was dispatched to Geotech (S.C.) Pty Ltd in Kawana for testing in
accordance with Australian Standard AS1289 Method for Testing Soils for Engineering Purposes. The
laboratory testing undertaken comprised Atterberg Limits, Linear Shrinkage and Percent Fines to assist with
material classification and to assess material properties. The Laboratory test certificate is attached.
Geotechnical laboratory test results are summarised below in Table 1.
Table 1: Laboratory Test Results (Soil Classification)
Atterberg Limits
TP No. Depth (m) Liquid Limit Plasticity Index Linear Shrinkage Fines Content
(%) (%) (%) (%)
TP3 0.0 – 0.3 50 22 13 52
Laboratory testing indicates soil from test pit TP3 (residual) is a sandy clay of medium to high plasticity. The
results indicate that residual material may be moderately reactive to moisture level changes.
3.0 DESCRIPTION OF EXISTING CONDITIONS
3.1 Desktop Review
The published geological map for the region 1 indicates that the bedrock in the general area is the Early to
Mid-Triassic aged Kin Kin Beds (pale green shading), described as “arenite, argillite, phyllite.” The site is
shown to be in close proximity to the contact between the Kin Kin Beds, and the younger Tertiary “Rhyolite”
material associated with Mount Cooroy itself (pale orange shading).
1
1:100,000 Gympie Special Geology Map, Sheet 9445, DME QLD, 1999
3/13
Page 4
Mr Ken Freeman 17385-001-Rev0
27 November 2017
Approximate site location
Text Figure 2: Extract from Gympie Geological Map
The Bowler soil test comprised two boreholes advanced using machine augering techniques to a depth of
2.4 m BGL (below ground level). These encountered a mixture of medium dense to dense clayey sand,
and very stiff to hard, low to medium plasticity, sandy clays. These were both logged as being brown to
red-brown in colour.
Groundwater was not encountered in the Bowler Geotech holes, with soils described as moist.
Prior to the construction of the existing house, Bowler Geotech classified the site as Class M in
accordance with AS2870, with a predicted surface movement (ys) due to soil moisture content variation of
around 30 mm.
3.2 Subsurface Conditions - Tectonic Test Pit Investigation
Subsurface materials at the investigation locations consisted of mostly medium to high plasticity silty clay,
being firm to stiff to 0.5 m depth, becoming very stiff to hard below. Exceptions to this were at TP1 (proposed
garage extension), where medium dense silty sand was encountered to 1.3 m depth; and in TP4 where
around 1.5 m depth of fill was encountered. Mostly the natural materials were grey to pale grey mottled
yellow and orange brown, with some red-brown coloured soils north-east of the existing house.
Where excavator bucket refusal occurred, this was interpreted as rockhead, and was inferred as highly
weathered, very low strength rhyolite. Soils above the inferred rockhead were inferred to be residual
material.
3.3 Topography
As illustrated by the contours in Text Figure 3 on the following page, moderately steep slopes of 20° to 25°
(36% to 47%) are present in the southern part of the lot (the flanks of Mount Cooroy) with the gradients
becoming progressively gentler towards the north (10° to 12° (18% to 21%)). Four gullies are present within
the lot boundary, mostly running south-north, and not in close proximity to the existing house or proposed
construction areas.
The Bowler investigation report noted that the original ground slope at the site of the house was
approximately 25% (14°). Measurements taken on site by Tectonic using a hand-held inclinometer indicate
the natural slopes on the eastern side of the house site are up to around 20˚ (36%), becoming flatter to the
4/13
Page 5
Mr Ken Freeman 17385-001-Rev0
27 November 2017
west and north of the house (approximately 12˚ to 15° (21% to 27 %)). Immediately north of the house and
existing pool there is an inferred fill batter approximately 2 m high and formed at 26˚ (49%).
Site conditions at the time of the investigation are shown in Text Figures 4 to 6, below and on the following
page.
Approximate house location
Text Figure 3: Image showing ground surface contours (courtesy Noosa Shire Council interactive maps website)
Possible two Swimming pool to be filled in
storey extension Fill batter
site
Area to be filled to same level
as top of existing pool
Text Figure 4: View of rear of house showing natural slope and area around swimming pool. Looking west and east
Proposed garage extension
Two-tiered rock wall
Text Figure 5: View of front of house, site of proposed porte cochere (looking NW); and proposed garage (looking E)
5/13
Page 6
Mr Ken Freeman 17385-001-Rev0
27 November 2017
Text Figure 6: View of platform formed for car port west of house, looking east
3.4 Groundwater
Groundwater was not encountered in the Bowler boreholes, or Tectonic test pits. No groundwater seepage
(‘springs’) was observed during the walk-over.
3.5 Surface Drainage
Natural surface drainage paths may be variable in the immediate vicinity of the proposed building envelope,
but natural drainage would be expected to follow ground surface contours to the north. The site is located
midslope on Mount Cooroy and is susceptible to surface runoff entering the site from the upslope
catchment. Surface water is expected to drain from the site considering the moderate to steep gradients and
relatively low permeability of the clayey soils and rock. No visible signs of soil erosion were observed during
the walkover.
3.6 Vegetation
In the vicinity of the house, and proposed areas for extensions, there were landscaped gardens present.
Vegetation included grass, plants, shrubs, and small trees. The garden at the rear (north) of the house
consisted of a level terrace (consisting of fill around 1.4 m deep) with a batter (26°) below. This batter did
not show any signs of slope instability at the time of the walk-over.
3.7 Buildings and Other Structures
The existing house comprised a split-level home over two storeys, with the upper level on the upslope side
forming the entrance. To the south-east of the main house was a garage, and east of the house in the
garden area was an office. At the rear (north) of the house was an existing swimming pool. On the southern
side of the driveway a two-tiered rock boulder retaining wall had been recently constructed, and was around
3.5 m high.
None of these existing structures showed signs of visible distress (i.e. cracking) at the time of the walk-over
which would indicate possible slope instability.
6/13
Page 7
Mr Ken Freeman 17385-001-Rev0
27 November 2017
4.0 ASSESSMENT OF LAND STABILITY
4.1 Existing Conditions
Noosa Shire Council (NSC) landslide hazard overlay mapping (Refer extract in Text Figure 7) indicates that
the lot has some areas assigned as being a “Landslide Hazard Area.”
Existing house
Text Figure 7: Extract from Noosa Shire Council Hazard Overlay (courtesy Noosa Shire Council Interactive Maps)
It should be noted that the NSC map is a broad-scale indication, applied at a coarse resolution, of the
potential landslide hazard only and is superseded by site specific assessment. The areas of the proposed
construction works, and the existing house are not designated as a “Landslide Hazard Area.”
4.2 Stability Assessment
The risk assessment for this project has been carried out following AGS 2007 Practice Note Guidelines for
Landslide Risk Management. Relative levels of risk and their implications are given in Table 2 on the
following page, and the Qualitative Terminology for Use in Assessing Risk to Property is also attached.
Table 2: Stability Risk Levels
Risk Level Example Implications(1)
Unacceptable without treatment. Extensive detailed investigation and research, planning
Very High
VH and implementation of treatment options essential to reduce risk to Low; may be too
Risk
expensive and not practical. Work likely to cost more than value of property.
Unacceptable without treatment. Detailed investigation, planning and implementation of
H High Risk treatment options required to reduce risk to Low. Work would cost a substantial sum in
relation to the value of the property.
May be tolerated in certain circumstances (subject to regulators’ approval) but requires
Moderate
M investigation, planning and implementation of treatment options to reduce risk to Low.
Risk
Treatment options to reduce to Low risk should be implemented as soon as practicable.
Usually acceptable to regulators. Where treatment has been required to reduce the risk
L Low Risk
to this level, ongoing maintenance required.
Very Low
VL Acceptable. Manage by normal slope maintenance procedures.
Risk
7/13
Page 8
Mr Ken Freeman 17385-001-Rev0
27 November 2017
Note: (1) The implications for a particular situation are to be determined by all parties to the risk assessment and
may depend on the nature of the property at risk; these are only given as a general guide.
Considering the existing site conditions (Refer Section 3), and subject to the implementation of
recommendations given below, it is our opinion that there is a Low (L) Risk of global slope instability affecting
the proposed development. Regulators (NSC) normally require that a Very Low or Low Risk of landslide
affecting the property must be demonstrated to enable development approval. Summarised in Table 3 is our
qualitative assessment of landslide risk for the development. A summary of qualitative terminology for use in
assessing risk to property is attached (taken from AGS 2007).
Table 3: Qualitative stability risk assessment
Assessed
Hazard Likelihood Consequence
Risk
Comments
The natural soils on site are generally at least
stiff/medium dense material, underlain by rock at
relatively shallow depth (<1.3 m BGL), no
groundwater was encountered in the previous
1: Shallow landslide through Bowler investigation or the recent test pits.
natural soils above foundation Unlikely Medium Low Therefore, it is considered Unlikely that a shallow
depth landslip would develop. However, the potential
impact from instability is assessed as Medium,. The
resultant risk would therefore be Low as per AGS
2007, subject to the implementation of
recommendations in Section 5.
No signs of existing instability in the fill embankment
were observed, and future fill is to be supported by
engineer designed retaining walls, therefore it is
2: Shallow failure through fill assessed that the likelihood of shallow failure in the
material in terrace on the Unlikely Minor Low fill is Unlikely. No buildings are planned in the filled
northern side of house area, therefore the consequence of the failure would
be Minor. The resultant risk is Low as per AGS
2007, subject to the implementation of
recommendations in Section 5.
The likelihood of a deep failure through the
weathered rock is assessed as Rare due to the
strength of the rock, apparent absence of
3: Deep seated landslide groundwater, and no evidence of existing instability
through weathered rock below Rare Major Low in the vicinity of the works. Although the
foundations consequence of such a failure would be Major, the
resultant risk is Low as per AGS 2007, subject to
the implementation of recommendations in Section
5.
The potential impacts on slope stability of the development components (including during earthworks) have
been assessed, and the measures recommended below in Section 5 have been designed to mitigate those
impacts.
8/13
Page 9
Mr Ken Freeman 17385-001-Rev0
27 November 2017
5.0 COMMENTS AND RECOMMENDATIONS
General recommendations to help maintain the stability of the site are given in the document “Some
Guidelines for Hillside Construction”, which is attached.
5.1 Building Locations
As indicated by concept drawings provided by the client, we understand that the largest potential structures
(possible future extension) will be located to the east side of the house, with smaller elements to the west,
south, and south-east. Should the proposed construction areas be amended, Tectonic must review this
stability assessment.
5.2 Earthworks
Based on provided information including a concept layout plan, survey drawing and discussions with the
client, the following cut/fill operations are anticipated:
Car port: a small cut in residual material is already present, approximately 1 m high on the upslope
side of the car port west of the house.
Rear of existing house: filling is anticipated to be at least 2.0 m high to the north side of the house
within and surrounding the existing pool.
Possible future extension of residence: a cut of up to 3 m on the upslope side of the building footprint,
and filling up to about 2.5 m (which will be retained) on the downslope side of the extension.
Tectonic must review the impacts on stability if cut/fill earthworks exceed these estimated depths/heights. All
fill batters and cuts greater than 1 m high should be retained by engineer designed and certified retaining
walls.
Following stripping of topsoil, and any organics/tree roots, the subgrade should be proof rolled using a
5 tonne roller to identify any soft/loose areas. Proof rolling in areas of cut may be deferred until after
excavation. Soft/loose areas should be over-excavated to a stiff foundation, and backfilled with compacted
fill as per the recommendations below. The stripped surfaces in fill areas should be assessed by a suitably
qualified geotechnical engineer prior to the commencement of filling.
Fill materials should be compacted at moisture contents within the range of -2% to +2% of optimum moisture
content for Standard Compaction. Confirmatory testing must be carried out at regular intervals and further
details for control and testing of fill are given in Australian Standard AS 3798-2007 “Guidelines on Earthworks
for Commercial and Residential Developments”. Select fill should have a maximum particle size of 100 mm
for an uncompacted layer thickness of 200 mm and shall be compacted by repeated rolling with a pad foot
roller to achieve a dry density ratio of at least 95% of the Standard Maximum Dry Density for cohesive soils,
or 70% Dry Density Index for any imported cohesionless soils.
Sloping ground must be ‘benched’ prior to placement of fill. Fill batters should be over-filled by 0.5 m
(horizontally) and then trimmed back to the well compacted material.
Rock may require ripping or breaking with pneumatic attachments in the area of the proposed future
residential extension, and the effects of vibration on adjacent structures should be taken in to account when
undertaking the work. The foundation details of the surrounding structures should be ascertained, to avoid
undermining the foundations during the excavation works. Text Figure 8 on page 12 provides guidance on
the zone of influence for footings to avoid undermining.
Temporary batter slopes should not exceed 1V:1H, and may need to be flatter if groundwater seepage is
encountered or if earthworks are carried out during a period of wet weather. The impact of surcharge loads
due to existing structures at the crest of any fill batter must also be considered during planning of
excavations.
Permanent batter slopes should be finished at a maximum grade of 1V:2H in stiff (or stiffer) natural material,
and controlled fill. If there is insufficient space to form such batters, retaining walls should be constructed.
Permanent batters will require erosion protection, e.g. revegetation or surface protection.
9/13
Page 10
Mr Ken Freeman 17385-001-Rev0
27 November 2017
5.3 Retaining Structures
Retaining structures for the proposed works must be engineer designed in accordance with AS4678-2002
Earth retaining structures, and must be founded as described in Section 5.4 below. The following
parameters may be adopted for retaining wall design.
Table 4: Retaining Wall Design Parameters
Lateral earth pressure coefficients
Unit Friction
Retained material weight angle
Ka Ko
(kN/m3) (Degrees) Kp
(Cantilever wall) (Non-yielding wall)
Existing fill material to
north of house (firm to 18 22 0.46 0.63 2.2
stiff silty clay)
Natural residual soils
(very stiff to hard silty 19 26 0.39 0.56 2.56
clay)
Highly weathered
22 35 0.27 0.43 3.69
rock
Note: These parameters do not include allowance for surcharge above the wall, or additional loads imposed
by sloping ground.
A retaining wall is recommended to support the cut adjacent to the proposed carport (Refer Text Figure 6).
Engineer design of retaining walls should include global stability modelling, which can be carried out by
Tectonic once retaining wall design details are available.
10/13
Page 11
Mr Ken Freeman 17385-001-Rev0
27 November 2017
5.4 Footing Design
There are several structures proposed , with differing founding specifications recommended for each. These
are given below in Table 5.
Table 5: Footing Design Details
Suitable Foundation Type Target Foundation Allowable Bearing
Renovation element Material Capacity
Proposed Carport High Level – Strip/pad/post Into very stiff clay 150 kPa
footing approximately 0.5 m BGL
Into medium dense silty
Proposed Porte Cochere High Levelfooting
- Strip/pad/post sand / very stiff clay 150 kPa
approximately 0.5 m BGL
High Level - Strip/pad Into medium dense silty
Proposed Garage footing sand 150 kPa
approximately 0.5 m BGL
Proposed retaining walls Reinforced concrete bored Socket minimum 1.0 m into
natural very stiff or hard End bearing: 400 kPa
north of house piles silty clay below fill
supporting fill platform Shaft friction: 30kPa
approximately 3 m BGL
Socket minimum 1.0 m into
Possible Future Two moderately weathered,
Storey Extension, Pool, Reinforced concrete bored very low strength rock End bearing: 1 MPa
and associated retaining piles, or mass excavated Approximately 1.5 m below
pad footings existing ground level Shaft friction: 90kPa
walls (depths may vary following
earthworks)
Foundation excavations must be inspected by a suitably qualified geotechnical engineer prior to placing steel
and pouring concrete.
Footing design must also account for potential soil reactivity, which was previously assessed as Class M by
Bowler.
11/13
Page 12
Mr Ken Freeman 17385-001-Rev0
27 November 2017
All footings should be founded such that they are not adversely affected by any adjacent excavations, batter
slopes, trenches, or retaining walls that are not designed to support building loads. Footings should found at
least below a plane extending 1 m horizontally from the base of trenches/batter slopes/excavations/retaining
walls, then rising up at 1V:1H, as illustrated in the following Text Figure 8.
Text Figure 8: Footing depth required to prevent undermining
Footing bases must be cleaned following mechanical excavation to expose undisturbed materials over the
full base area.
If any soil conditions encountered during construction are found to differ from those noted above, Tectonic
must be notified immediately and an inspection carried out to determine if changes to footing design are
required.
5.5 Drainage
The garage extension, carport, and porte cochere should not add significantly to the stormwater catchment
on site, and provided there is capacity, run-off could be directed to the existing provisions on site. If the two
storey extension is to be constructed, then adequate site drainage must be installed to ensure that
stormwater runoff is directed away from the proposed structure and discharged at least 10 m downslope. It
is recommended that surface drainage be installed around the entirety of the house, e.g., swales, or grated
channel drains, to divert any run-off away from the building walls and footings.
Subsurface drainage must also be installed behind all retaining walls to prevent development of hydrostatic
pressure.
For the proposed filling works north of the existing house, a specific arrangement is recommended. It is
understood the existing pool structure will not be demolished, but is to be in-filled. To prevent saturation of
the pool backfill, it is recommended that the front (northern) wall of the pool is broken out, and a 150 mm
thick layer of drainage gravel placed in the base of the pool with an overlying layer of geofabric. The water
should be piped from a collection pit to the extremities of the fill embankment (discharging away from fill
batters), or through weep holes/outlets through the retaining walls. The pool should not be drained through
the bottom as this may saturate underlying foundation soils.
All excess stormwater collected from the site, must be directed by pipes or rock-lined channels to a natural
drainage line at least 10 m down slope of the proposed house. The drainage outlet should be protected by a
stacked or grouted rock weir, or similar, to dissipate stormwater flows. Subsurface disposal of stormwater
must not be undertaken.
12/13
Page 13
Mr Ken Freeman 17385-001-Rev0
27 November 2017
6.0 SUMMARY & CONCLUSIONS
Based on the findings of our assessment we consider, from a geotechnical viewpoint, that the site is suitable
for the proposed development and that there should be a Low Risk of slope instability. This advice is subject
to implementation of the recommendations given in this report, in particular:
All fill batters and cuts greater than 1 m high should be retained by engineer designed and certified
retaining walls.
The carport, garage, and porte cochere should have as a minimum high level footings taken down to
medium dense (or denser) / very stiff (or stiffer) material at approximately 0.5 m BGL
The retaining walls for the fill area north of the house will require bored piles or similar, socketing at
least 1 m in to very stiff or hard residual clay below the existing fill, approximately 3 m BGL
The possible two storey extension will require bored piers taken at least 1 m in to weathered very
low strength rock (or stronger).
Foundation excavations and stripped subgrades in fill areas must be inspected by a suitably qualified
geotechnical engineer
Ensuring that stormwater flow is directed at least 10 m down slope of the building envelope,
especially regarding the possible two storey extension to the north-east; and the filling work north of
the house
The front wall of the existing swimming pool should be broken out and drainage installed to prevent
saturation of pool backfill and foundation soils.
7.0 LIMITATIONS
Your attention is drawn to the document Limitations, which is attached to this letter report.
Please contact the undersigned should you wish to discuss any of the above matters.
Yours faithfully,
TECTONIC GEOTECHNICAL PTY LTD
Robert Gibb BSc (Hons) Scott Davis BEng CPEng RPEQ 16439
Engineering Geologist Senior Geotechnical Engineer
Attachments: Site Plan
Test Pit Logs and Explanatory Notes
Laboratory Test Results
Qualitative Terminology for Use in Assessing Risk to Property
Some Guidelines for Hillside Construction
Limitations
13/13
Page 14
APPROXIMATE AREA FOR
Tectonic Geotechnical Pty Ltd
FILLING
12°
12°
PO Box 899
Buderim Qld 4556
M: 0437 755 700 / 0437 756 711
TP5
POSSIBLE AREA PROJECT:
FOR TWO STOREY
EXTENSION 400 COOROY MOUNTAIN ROAD
PROPOSED EXTENSION TO
TP4 RESIDENCE
TITLE:
TP3
SITE PLAN
TP2 CLIENT:
TP6 MR KEN FREEMAN
DRAWN: DATE:
RKG 23/11/2017
CHECKED: DATE:
SKD 27/11/2017
SCALE:
NTS
LEGEND:
TP1
APPROXIMATE TEST PIT
LOCATIONS
PROJECT NO.: FIGURE: REV:
Base plan taken from plan supplied by client, 2 November 2017 17385-001 1 0
Page 15
Borehole No.
TP1
Page 1 of 1
Engineering Log - Test Pit Project No.: 17385
Client: Mr Ken Freeman Commenced: 09/11/2017
Project Name: Proposed Residential Extensions Completed: 09/11/2017
Hole Location: 400 Cooroy Mountain Road, Cooroy Logged By: RKG
Hole Position: 494991.0 m E 7077035.0 m N MGA94 Zone 56 Checked By: SKD
Equipment Type and Model: 6t Excavator RL Surface: 167.50 m
Excavation Dimensions: 2.5 m Long 0.5 m Wide Datum: AHD Operator: Traxx
Excavation Information Soil Description Observations
Relative Density
Classification
Penetration
Pocket
Consistency
Graphic Log
Samples Material Description
Penetrometer Structure and
Condition
Recovery
Tests soil type: plasticity or particle characteristics,
Moisture
UCS Additional Observations
Symbol
Method
secondary and minor components, colour
Water
Remarks RL Depth (kPa)
(m) (m)
100
200
300
400
500
CI Sandy CLAY (RESIDUAL) medium plasticity, 0.00: Ground level 2.0m below original
red brown, fine to medium grained sand surface in cutting
St
SM Silty SAND (RESIDUAL) fine grained, pale
yellow brown to orange brown, with medium to
DS coarse sized sub-angular to sub-rounded
Not Encountered
167.0
0.4-0.6m gravel
0.5
MD
M
E
becoming grey mottled yellow and orange
brown, tending to extremely weathered
material
166.5
1.0
D
TECTONIC 2.00.1 LIB.GLB Log 1 TECTONIC BOREHOLE 17385.GPJ <<DrawingFile>> 24/11/2017 08:37 8.30.004 Datgel Lab and In Situ Tool - DGD | Lib: Tectonic 2.00.1 2016-02-17 Prj: Tectonic 2.00 2016-02-16
Hole Terminated at 1.30 m
Bucket Refusal
166.0
1.5
165.5
2.0
165.0
2.5
Method Penetration Water Samples and Tests Moisture Condition Consistency/Relative Density
N - Natural Exposure No resistance Level (Date) U - Undisturbed Sample D - Dry VS - Very Soft
X - Existing Excavation ranging to D - Disturbed Sample M - Moist S - Soft
BH - Backhoe Bucket refusal Inflow CBR- CBR Mould Sample W - Wet F - Firm
R - Ripper VSt - Very Stiff
E - Excavator H - Hard
Plastic Limit VL - Very Loose
L - Loose
Classification Symbols < PL MD - Medium Dense
and Soil Descriptions = PL D - Dense
Based on Unified Soil < PL VD - Very Dense
Classification System
Page 16
Borehole No.
TP2
Page 1 of 1
Engineering Log - Test Pit Project No.: 17385
Client: Mr Ken Freeman Commenced: 09/11/2017
Project Name: Proposed Residential Extensions Completed: 09/11/2017
Hole Location: 400 Cooroy Mountain Road, Cooroy Logged By: RKG
Hole Position: 494985.0 m E 7077061.0 m N MGA94 Zone 56 Checked By: SKD
Equipment Type and Model: 6t Excavator RL Surface: 164.50 m
Excavation Dimensions: 2.5 m Long 0.5 m Wide Datum: AHD Operator: Traxx
Excavation Information Soil Description Observations
Relative Density
Classification
Penetration
Pocket
Consistency
Graphic Log
Samples Material Description
Penetrometer Structure and
Condition
Recovery
Tests soil type: plasticity or particle characteristics,
Moisture
UCS Additional Observations
Symbol
Method
secondary and minor components, colour
Water
Remarks RL Depth (kPa)
(m) (m)
100
200
300
400
500
CH Sandy CLAY (RESIDUAL) high plasticity, 0.00: Ground level 0.3m below original
orange brown, fine grained sand, with silt and surface in cutting
medium sized sub-angular gravel, with
rootlets St to
M
VSt
Not Encountered
RHYOLITE, highly weathered, pale yellow
164.0
0.5 brown to red brown, very low strength.
Recovered as cobbles 30-60mm in size
E
163.5
1.0
RHYOLITE, moderately weathered, grey
TECTONIC 2.00.1 LIB.GLB Log 1 TECTONIC BOREHOLE 17385.GPJ <<DrawingFile>> 24/11/2017 08:38 8.30.004 Datgel Lab and In Situ Tool - DGD | Lib: Tectonic 2.00.1 2016-02-17 Prj: Tectonic 2.00 2016-02-16
brown to yellow, very low strength. Recovered
as cobbles
Hole Terminated at 1.20 m
Bucket Refusal
163.0
1.5
162.5
2.0
162.0
2.5
Method Penetration Water Samples and Tests Moisture Condition Consistency/Relative Density
N - Natural Exposure No resistance Level (Date) U - Undisturbed Sample D - Dry VS - Very Soft
X - Existing Excavation ranging to D - Disturbed Sample M - Moist S - Soft
BH - Backhoe Bucket refusal Inflow CBR- CBR Mould Sample W - Wet F - Firm
R - Ripper VSt - Very Stiff
E - Excavator H - Hard
Plastic Limit VL - Very Loose
L - Loose
Classification Symbols < PL MD - Medium Dense
and Soil Descriptions = PL D - Dense
Based on Unified Soil < PL VD - Very Dense
Classification System
Page 17
Borehole No.
TP3
Page 1 of 1
Engineering Log - Test Pit Project No.: 17385
Client: Mr Ken Freeman Commenced: 09/11/2017
Project Name: Proposed Residential Extensions Completed: 09/11/2017
Hole Location: 400 Cooroy Mountain Road, Cooroy Logged By: RKG
Hole Position: 494632.0 m E 7071061.0 m N MGA94 Zone 56 Checked By: SKD
Equipment Type and Model: 6t Excavator RL Surface: 162.50 m
Excavation Dimensions: 2.5 m Long 0.5 m Wide Datum: AHD Operator: Traxx
Excavation Information Soil Description Observations
Relative Density
Classification
Penetration
Pocket
Consistency
Graphic Log
Samples Material Description
Penetrometer Structure and
Condition
Recovery
Tests soil type: plasticity or particle characteristics,
Moisture
UCS Additional Observations
Symbol
Method
secondary and minor components, colour
Water
Remarks RL Depth (kPa)
(m) (m)
100
200
300
400
500
DS CH Sandy CLAY (RESIDUAL) high plasticity, 0.00: Ground level 0.2m below original
0-0.3m orange brown, fine grained sand, with silt and surface in cutting
medium sized sub-angular gravel St to
VSt
becoming red brown, with sub-angular M
cobbles up to 60mm in size
Not Encountered
162.0
0.5 VSt
E
RHYOLITE, highly weathered, pale yellow
brown, to red brown, very low strength.
Recovered as cobbles 30-60mm in size
161.5
1.0
TECTONIC 2.00.1 LIB.GLB Log 1 TECTONIC BOREHOLE 17385.GPJ <<DrawingFile>> 24/11/2017 08:39 8.30.004 Datgel Lab and In Situ Tool - DGD | Lib: Tectonic 2.00.1 2016-02-17 Prj: Tectonic 2.00 2016-02-16
Hole Terminated at 1.30 m
Bucket Refusal
161.0
1.5
160.5
2.0
160.0
2.5
Method Penetration Water Samples and Tests Moisture Condition Consistency/Relative Density
N - Natural Exposure No resistance Level (Date) U - Undisturbed Sample D - Dry VS - Very Soft
X - Existing Excavation ranging to D - Disturbed Sample M - Moist S - Soft
BH - Backhoe Bucket refusal Inflow CBR- CBR Mould Sample W - Wet F - Firm
R - Ripper VSt - Very Stiff
E - Excavator H - Hard
Plastic Limit VL - Very Loose
L - Loose
Classification Symbols < PL MD - Medium Dense
and Soil Descriptions = PL D - Dense
Based on Unified Soil < PL VD - Very Dense
Classification System
Page 18
Borehole No.
TP4
Page 1 of 1
Engineering Log - Test Pit Project No.: 17385
Client: Mr Ken Freeman Commenced: 09/11/2017
Project Name: Proposed Residential Extensions Completed: 09/11/2017
Hole Location: 400 Cooroy Mountain Road, Cooroy Logged By: RKG
Hole Position: 494954.0 m E 7077080.0 m N MGA94 Zone 56 Checked By: SKD
Equipment Type and Model: 6t Excavator RL Surface: 162.00 m
Excavation Dimensions: 2.5 m Long 0.5 m Wide Datum: AHD Operator: Traxx
Excavation Information Soil Description Observations
Relative Density
Classification
Penetration
Pocket
Consistency
Graphic Log
Samples Material Description
Penetrometer Structure and
Condition
Recovery
Tests soil type: plasticity or particle characteristics,
Moisture
UCS Additional Observations
Symbol
Method
secondary and minor components, colour
Water
Remarks RL Depth (kPa)
(m) (m)
100
200
300
400
500
CI Silty CLAY (FILL), medium plasticity, red
brown, trace of fine sized sub-angular gravel
F to
St
161.5
0.5
DS becoming dark grey mottled yellow and pale
0.5-0.7m red
H
161.0
1.0
CI Silty CLAY (INFERRED NATURAL
TECTONIC 2.00.1 LIB.GLB Log 1 TECTONIC BOREHOLE 17385.GPJ <<DrawingFile>> 24/11/2017 08:40 8.30.004 Datgel Lab and In Situ Tool - DGD | Lib: Tectonic 2.00.1 2016-02-17 Prj: Tectonic 2.00 2016-02-16
TOPSOIL), medium plasticity, dark brown,
with fine grained sand and rootlets
F
Not Encountered
M
E
CH Sandy CLAY (RESIDUAL), high plasticity, red
160.5
1.5 brown mottled grey and yellow, fine grained
sand, with silt and fine to medium sized
sub-angular gravel
DS
1.6-1.8m
VSt
160.0
2.0
H
159.5
2.5
becoming grey mottled yellow brown, with
sub-rounded to sub-angular cobbles
60-100mm in size
Hole Terminated at 2.80 m
Machine Limit
Method Penetration Water Samples and Tests Moisture Condition Consistency/Relative Density
N - Natural Exposure No resistance Level (Date) U - Undisturbed Sample D - Dry VS - Very Soft
X - Existing Excavation ranging to D - Disturbed Sample M - Moist S - Soft
BH - Backhoe Bucket refusal Inflow CBR- CBR Mould Sample W - Wet F - Firm
R - Ripper VSt - Very Stiff
E - Excavator H - Hard
Plastic Limit VL - Very Loose
L - Loose
Classification Symbols < PL MD - Medium Dense
and Soil Descriptions = PL D - Dense
Based on Unified Soil < PL VD - Very Dense
Classification System
Page 19
Borehole No.
TP5
Page 1 of 1
Engineering Log - Test Pit Project No.: 17385
Client: Mr Ken Freeman Commenced: 09/11/2017
Project Name: Proposed Residential Extensions Completed: 09/11/2017
Hole Location: 400 Cooroy Mountain Road, Cooroy Logged By: RKG
Hole Position: 494932.0 m E 7077092.0 m N MGA94 Zone 56 Checked By: SKD
Equipment Type and Model: 6t Excavator RL Surface: 159.00 m
Excavation Dimensions: 2.5 m Long 0.5 m Wide Datum: AHD Operator: Traxx
Excavation Information Soil Description Observations
Relative Density
Classification
Penetration
Pocket
Consistency
Graphic Log
Samples Material Description
Penetrometer Structure and
Condition
Recovery
Tests soil type: plasticity or particle characteristics,
Moisture
UCS Additional Observations
Symbol
Method
secondary and minor components, colour
Water
Remarks RL Depth (kPa)
(m) (m)
100
200
300
400
500
Silty CLAY (TOPSOIL), medium plasticity, pale
brown, with rootlets F to
CH D
Silty CLAY (RESIDUAL) high plasticity, brown St
CH Silty CLAY (RESIDUAL) high plasticity, grey
mottled orange, with fine grained sand, trace
of fine to medium sized sub-angular gravel
158.5
St
0.5
DS
0.5-0.7m M
Not Encountered
CH Sandy CLAY (RESIDUAL) high plasticity, pale
158.0
1.0 grey mottled yellow, fine to coarse grained
E
DS sand, with silt and fine to coarse sized angular
TECTONIC 2.00.1 LIB.GLB Log 1 TECTONIC BOREHOLE 17385.GPJ <<DrawingFile>> 24/11/2017 08:41 8.30.004 Datgel Lab and In Situ Tool - DGD | Lib: Tectonic 2.00.1 2016-02-17 Prj: Tectonic 2.00 2016-02-16
1-1.2m gravel
W
VSt
157.5
1.5
becoming dark grey, with cobbles and
boulders
M
RHYOLITE, highly weathered, pale yellow
157.0
2.0 brown to red brown, very low strength,
recovered as cobbles 30-60mm in size
Hole Terminated at 2.00 m
Bucket Refusal
156.5
2.5
Method Penetration Water Samples and Tests Moisture Condition Consistency/Relative Density
N - Natural Exposure No resistance Level (Date) U - Undisturbed Sample D - Dry VS - Very Soft
X - Existing Excavation ranging to D - Disturbed Sample M - Moist S - Soft
BH - Backhoe Bucket refusal Inflow CBR- CBR Mould Sample W - Wet F - Firm
R - Ripper VSt - Very Stiff
E - Excavator H - Hard
Plastic Limit VL - Very Loose
L - Loose
Classification Symbols < PL MD - Medium Dense
and Soil Descriptions = PL D - Dense
Based on Unified Soil < PL VD - Very Dense
Classification System
Page 20
Borehole No.
TP6
Page 1 of 1
Engineering Log - Test Pit Project No.: 17385
Client: Mr Ken Freeman Commenced: 09/11/2017
Project Name: Proposed Residential Extensions Completed: 09/11/2017
Hole Location: 400 Cooroy Mountain Road, Cooroy Logged By: RKG
Hole Position: 494938.0 m E 7077069.0 m N MGA94 Zone 56 Checked By: SKD
Equipment Type and Model: 6t Excavator RL Surface: 164.00 m
Excavation Dimensions: 2.5 m Long 0.5 m Wide Datum: AHD Operator: Traxx
Excavation Information Soil Description Observations
Relative Density
Classification
Penetration
Pocket
Consistency
Graphic Log
Samples Material Description
Penetrometer Structure and
Condition
Recovery
Tests soil type: plasticity or particle characteristics,
Moisture
UCS Additional Observations
Symbol
Method
secondary and minor components, colour
Water
Remarks RL Depth (kPa)
(m) (m)
100
200
300
400
500
CI Sandy CLAY (RESIDUAL) medium plasticity, 0.00: Ground level 1.3m below original
red brown, fine grained sand, with silt and surface in cutting
medium sized sub-angular gravel, trace of fine
grained sand F to
St
CH Sandy CLAY (RESIDUAL) high plasticity,
Not Encountered
163.5
0.5 yellow brown to orange brown, fine grained
sand with silt and fine sized sub-angular
gravel, trace of fine to medium grained sand
M
E
VSt
163.0
1.0
TECTONIC 2.00.1 LIB.GLB Log 1 TECTONIC BOREHOLE 17385.GPJ <<DrawingFile>> 24/11/2017 08:42 8.30.004 Datgel Lab and In Situ Tool - DGD | Lib: Tectonic 2.00.1 2016-02-17 Prj: Tectonic 2.00 2016-02-16
VSt
to H
with cobble sized corestones, dark grey,
tending to extremely weathered material
Hole Terminated at 1.30 m
Bucket Refusal
162.5
1.5
162.0
2.0
161.5
2.5
Method Penetration Water Samples and Tests Moisture Condition Consistency/Relative Density
N - Natural Exposure No resistance Level (Date) U - Undisturbed Sample D - Dry VS - Very Soft
X - Existing Excavation ranging to D - Disturbed Sample M - Moist S - Soft
BH - Backhoe Bucket refusal Inflow CBR- CBR Mould Sample W - Wet F - Firm
R - Ripper VSt - Very Stiff
E - Excavator H - Hard
Plastic Limit VL - Very Loose
L - Loose
Classification Symbols < PL MD - Medium Dense
and Soil Descriptions = PL D - Dense
Based on Unified Soil < PL VD - Very Dense
Classification System
Page 21
TERMS USED ON LOGS
DRILLING/EXCAVATION METHOD
AD* Auger Drilling RD Rotary Blade or Drag bit NQ Diamond Core - 47 mm
*V V-Bit RT Rotary Tri-cone bit NMLC Diamond Core - 52 mm
*T TC-Bit RA Rotary Air HQ Diamond Core - 63 mm
HA Hand Auger HMLC Diamond Core – 63mm
ADH Hollow Auger BH Tractor Mounted Backhoe
HA Hand Auger EX Tracked Hydraulic Excavator
WATER
GROUNDWATER NOT The observation of groundwater, whether present or not, was not possible due to drilling water,
OBSERVED surface seepage or cave in of the borehole/test pit.
GROUNDWATER NOT The borehole/test pit was dry soon after excavation. However, groundwater could be present in
ENCOUNTERED less permeable strata. Inflow may have been observed had the borehole/test pit been left open
for a longer period.
SAMPLING AND TESTING
SPT Standard Penetration Test to AS1289.6.3.1-2004
5,4,10 N=14 5,4,10 = Blows per 150mm. N = Blows per 300mm penetration following 150mm seating
30/65mm Where practical refusal occurs, the blows and penetration for that interval are reported
RW Penetration occurred under the rod weight only
HW Penetration occurred under the hammer and rod weight only
HB Hammer double bouncing on anvil
DS Disturbed sample
BDS Bulk disturbed sample
FV Field vane shear test expressed as uncorrected shear strength (sv = peak value, sr = residual value)
PP Pocket penetrometer test expressed as instrument reading in kPa
U50 Thin walled tube sample - number indicates nominal sample diameter in millimetres
DCP Dynamic cone penetration test
CPT Electronic cone penetration test
CPTu Electronic cone penetration test with pore pressure (u) measurement
Rev0
October 2013
Page 22
METHOD OF SOIL DESCRIPTION
USED ON LOGS
CLASSIFICATION AND INFERRED STRATIGRAPHY
Soil is classified and described in borehole and test pit logs using the preferred method given in AS1726 – 2017.
The material properties are assessed in the field by visual/tactile methods.
Particle Size Plasticity Properties
Major Sub Division Particle Size
Division
BOULDERS > 200 mm
COBBLES 63 to 200 mm
Coarse 19 to 63 mm
GRAVEL Medium 6.7 to 19 mm
Fine 2.36 to 6.7 mm
Coarse 0.6 to 2.36 mm
SAND Medium 0.21 to 0.6 mm
Fine 0.075 to 0.21
SILT 0.002 to 0.075
CLAY < 0.002 mm
NOTE: The U line is an approximate upper bound for most materials.
Data which plot above the U line may represent unusual/problem soil
behavior, or unreliable data and should be considered carefully.
MOISTURE CONDITION AS1726 - 2017
Symbol Term Description
D Dry Sands and gravels are free flowing. Clays & Silts may be brittle or friable and powdery.
M Moist Soils are darker than in the dry condition & may feel cool. Sands and gravels tend to cohere.
W Wet Soils exude free water. Sands and gravels tend to cohere.
CONSISTENCY AND DENSITY AS1726 - 2017
Symbol Term Undrained Shear Symbol Term Density Index % SPT “N” #
Strength
VS Very Soft 0 to 12 kPa VL Very Loose Less than 15 0 to 4
S Soft 12 to 25 kPa L Loose 15 to 35 4 to 10
F Firm 25 to 50 kPa MD Medium Dense 35 to 65 10 to 30
St Stiff 50 to 100 kPa D Dense 65 to 85 30 to 50
VSt Very Stiff 100 to 200 kPa VD Very Dense Above 85 Above 50
H Hard Above 200 kPa
In the absence of test results, consistency and density may be assessed from correlations with the observed behaviour of
the material.
# SPT correlations are not stated in AS1726 – 2017, and may be subject to corrections for overburden pressure and
equipment type.
Rev1
October 2017
Page 23
METHOD OF ROCK DESCRIPTION USED ON LOGS
CLASSIFICATION AND INFERRED STRATIGRAPHY
Rock is classified and described in borehole and test pit logs using the preferred method given in AS1726 – 2017.
The material properties are assessed in the field by visual/tactile methods.
STRENGTH
Point Load
Symbol Term Index, Is(50) Field Guide
(MPa)
VL Very 0.03 to 0.1 Material crumbles under firm blows with sharp end of pick; can be peeled
Low with knife; too hard to cut a triaxial sample by hand. Pieces up to 30 mm
can be broken by finger pressure.
L Low 0.1 to 0.3 Easily scored with a knife; indentations 1 mm to 3 mm show in the specimen
with firm blows of pick point; has dull sound under hammer. A piece of core 150
mm long by 50 mm diameter may be broken by hand. Sharp edges of core may
be friable and break during handling.
M Medium 0.3 to 1 Readily scored with a knife; a piece of core 150 mm long by 50 mm diameter
can be broken by hand with difficulty.
H High 1 to 3 A piece of core 150 mm long by 50 mm diameter cannot be broken by hand but
can be broken with pick with a single firm blow; rock rings under hammer.
VH Very 3 to 10 Hand specimen breaks with pick after more than one blow; rock rings under
High hammer.
EH Extremely >10 Specimen requires many blows with geological pick to break through intact
High material; rock rings under hammer.
Relationship between Is(50) and UCS (unconfined compressive strength) will vary with rock type and strength, and
should be determined on a site-specific basis. UCS is typically 10 to 30 x Is(50), but can be as low as 5.
ROCK MATERIAL WEATHERING
Symbol Term Field Guide
Soil developed on extremely weathered rock; the mass structure and
Residual
RS substance fabric are no longer evident; there is a large change in volume
Soil but the soil has not been significantly transported.
Extremely Rock is weathered to such an extent that it has soil properties - i.e. it either
EW
Weathered disintegrates or can be remoulded, in water.
Whole of rock is discoloured, usually by iron staining or bleaching to the
extent that the colour of the original rock is not recognizable. Rock strength
Highly
HW is significantly changed by weathering. Porosity may be increased by
Weathered
leaching, or may be decreased due to deposition of weathering products in
Distinctly
DW pores.
Weathered
Whole of rock is discoloured, usually by iron staining or bleaching to the
Moderately extent that the colour of the original rock is not recognizable; but shows little
MW
Weathered or no change of strength from fresh rock.
Slightly Rock is slightly discoloured but shows little or no change of strength relative
SW
Weathered to fresh rock.
FR Fresh Rock shows no sign of decomposition or staining.
ABBREVIATIONS FOR DEFECT TYPES AND DESCRIPTIONS
Defect Type Coating or Infilling Roughness
BP Bedding parting Cn Clean POL Polished
X Foliation Sn Stain S Smooth
C Contact Vr Veneer SL Slickensided
L Cleavage Ct Coating or Infill S Smooth
JT Joint Clay Clay RF Rough
SS/SZ Sheared seam/zone (Fault) Fe Iron oxide VR Very rough
Qz Quartz Planarity
CS/CZ Crushed seam/zone (Fault)
DS/DZ Decomposed seam/zone PR Planar
IS/IZ Infilled seam/zone UN Undulating
S Schistocity ST Stepped
V Vein
DB Drilling break
Rev3
October 2017
Page 24
Quality of Materials Report
Client: Tectonic Geotechnical Pty Ltd Report Number: G17001 - 233/1
Client Address: PO Box 899 Buderim QLD 4556
Job Number: G17001 Report Date: 20/11/2017
Project: Laboratory Testing Samples Supplied Order Number: -
Location Project No:17385 , Cooroy Mountain Road Page 1 of 1
Lab No: 110338 Sample Location
Date Sampled: 9/11/2017 Test Pit 3
Date Tested: 17/11/2017 Depth 0.0 - 0.3m
Sampled By: Client Supplied 14/11/17
Sample Method: N/A
Material Source: Site Spec Description: -
For Use As: - Lot Number: -
Remarks: - Spec Number: -
A.S. Sieve Sizes Specification Percent Specification
Minimum Passing Maximum
Test Method: AS1289.3.6.1
75.00 mm
53.00 mm
37.50 mm
26.50 mm
19.00 mm
13.2 mm
9.50 mm
6.7 mm
4.75 mm
2.36 mm
1.18 mm
0.600 mm
0.425 mm
0.300 mm
0.150 mm
0.075 mm 52
Atterberg Tests Test Method Specification Result Specification
Minimum Maximum
Liquid Limit (%) AS1289.3.1.2 50
Plastic Limit (%) AS1289.3.2.1 28
Plasticity Index AS1289.3.3.1 22
Linear Shrinkage (%) AS1289.3.4.1 13.0
Approved Signatory Form Number
Accredited for compliance with ISO/IEC 17025-
Testing REP AQUAL-1-7
Mel Burnett
NATA Accred No:1551
Page 25
PRACTICE NOTE GUIDELINES FOR LANDSLIDE RISK MANAGEMENT 2007
APPENDIX C: LANDSLIDE RISK ASSESSMENT
QUALITATIVE TERMINOLOGY FOR USE IN ASSESSING RISK TO PROPERTY
QUALITATIVE MEASURES OF LIKELIHOOD
Approximate Annual Probability
Implied Indicative Landslide
Description Descriptor Level
Indicative Notional Recurrence Interval
Value Boundary
10-1 5x10-2
10 years The event is expected to occur over the design life. ALMOST CERTAIN A
20 years The event will probably occur under adverse conditions over the
-2
10 100 years
design life.
LIKELY B
-3
-3 5x10 200 years
10 1000 years The event could occur under adverse conditions over the design life. POSSIBLE C
5x10-4 2000 years
The event might occur under very adverse circumstances over the
10-4 10,000 years
design life.
UNLIKELY D
-5 5x10-5 20,000 years
10 The event is conceivable but only under exceptional circumstances
100,000 years RARE E
over the design life.
-6 5x10-6 200,000 years
10 1,000,000 years The event is inconceivable or fanciful over the design life. BARELY CREDIBLE F
Note: (1) The table should be used from left to right; use Approximate Annual Probability or Description to assign Descriptor, not vice versa.
QUALITATIVE MEASURES OF CONSEQUENCES TO PROPERTY
Approximate Cost of Damage
Description Descriptor Level
Indicative Notional
Value Boundary
Structure(s) completely destroyed and/or large scale damage requiring major engineering works for
200% CATASTROPHIC 1
stabilisation. Could cause at least one adjacent property major consequence damage.
100%
Extensive damage to most of structure, and/or extending beyond site boundaries requiring significant
60% MAJOR 2
stabilisation works. Could cause at least one adjacent property medium consequence damage.
40%
Moderate damage to some of structure, and/or significant part of site requiring large stabilisation works.
20% MEDIUM 3
Could cause at least one adjacent property minor consequence damage.
10%
5% 1% Limited damage to part of structure, and/or part of site requiring some reinstatement stabilisation works. MINOR 4
Little damage. (Note for high probability event (Almost Certain), this category may be subdivided at a
0.5% INSIGNIFICANT 5
notional boundary of 0.1%. See Risk Matrix.)
Notes: (2) The Approximate Cost of Damage is expressed as a percentage of market value, being the cost of the improved value of the unaffected property which includes the land plus the
unaffected structures.
(3) The Approximate Cost is to be an estimate of the direct cost of the damage, such as the cost of reinstatement of the damaged portion of the property (land plus structures), stabilisation
works required to render the site to tolerable risk level for the landslide which has occurred and professional design fees, and consequential costs such as legal fees, temporary
accommodation. It does not include additional stabilisation works to address other landslides which may affect the property.
(4) The table should be used from left to right; use Approximate Cost of Damage or Description to assign Descriptor, not vice versa
Australian Geomechanics Vol 42 No 1 March 2007
Form No. 68039
68039 RL2Risk
Landslide August 2010
Management Issued 10/7/07
Page 26
PRACTICE NOTE GUIDELINES FOR LANDSLIDE RISK MANAGEMENT 2007
APPENDIX C: – QUALITATIVE TERMINOLOGY FOR USE IN ASSESSING RISK TO PROPERTY (CONTINUED)
QUALITATIVE RISK ANALYSIS MATRIX – LEVEL OF RISK TO PROPERTY
LIKELIHOOD CONSEQUENCES TO PROPERTY (With Indicative Approximate Cost of Damage)
Indicative Value of 1: CATASTROPHIC 2: MAJOR 3: MEDIUM 4: MINOR 5:
Approximate Annual 200% 60% 20% 5% INSIGNIFICANT
Probability 0.5%
A – ALMOST CERTAIN 10-1 VH VH VH H M or L (5)
-2
B - LIKELY 10 VH VH H M L
C - POSSIBLE 10-3 VH H M M VL
D - UNLIKELY 10-4 H M L L VL
-5
E - RARE 10 M L L VL VL
-6
F - BARELY CREDIBLE 10 L VL VL VL VL
Notes: (5) For Cell A5, may be subdivided such that a consequence of less than 0.1% is Low Risk.
(6) When considering a risk assessment it must be clearly stated whether it is for existing conditions or with risk control measures which may not be implemented at the current
time.
RISK LEVEL IMPLICATIONS
Risk Level Example Implications (7)
Unacceptable without treatment. Extensive detailed investigation and research, planning and implementation of treatment
VH VERY HIGH RISK options essential to reduce risk to Low; may be too expensive and not practical. Work likely to cost more than value of the
property.
Unacceptable without treatment. Detailed investigation, planning and implementation of treatment options required to reduce
H HIGH RISK
risk to Low. Work would cost a substantial sum in relation to the value of the property.
May be tolerated in certain circumstances (subject to regulator’s approval) but requires investigation, planning and
M MODERATE RISK implementation of treatment options to reduce the risk to Low. Treatment options to reduce to Low risk should be
implemented as soon as practicable.
Usually acceptable to regulators. Where treatment has been required to reduce the risk to this level, ongoing maintenance is
L LOW RISK
required.
Acceptable. Manage by normal slope maintenance procedures.
VL VERY LOW RISK
Note: (7) The implications for a particular situation are to be determined by all parties to the risk assessment and may depend on the nature of the property at risk; these are only
given as a general guide.
Australian Geomechanics Vol 42 No 1 March 2007
Form No. Landslide
68039 68039 RL2Risk
August 2010
Management Issued 10/7/07
Page 27
PRACTICE NOTE GUIDELINES FOR LANDSLIDE RISK MANAGEMENT 2007
APPENDIX G - SOME GUIDELINES FOR HILLSIDE CONSTRUCTION
GOOD ENGINEERING PRACTICE POOR ENGINEERING PRACTICE
ADVICE
GEOTECHNICAL Obtain advice from a qualified, experienced geotechnical practitioner at early Prepare detailed plan and start site works before
ASSESSMENT stage of planning and before site works. geotechnical advice.
PLANNING
SITE PLANNING Having obtained geotechnical advice, plan the development with the risk Plan development without regard for the Risk.
arising from the identified hazards and consequences in mind.
DESIGN AND CONSTRUCTION
Use flexible structures which incorporate properly designed brickwork, timber Floor plans which require extensive cutting and
or steel frames, timber or panel cladding. filling.
HOUSE DESIGN
Consider use of split levels. Movement intolerant structures.
Use decks for recreational areas where appropriate.
SITE CLEARING Retain natural vegetation wherever practicable. Indiscriminately clear the site.
ACCESS & Satisfy requirements below for cuts, fills, retaining walls and drainage. Excavate and fill for site access before
DRIVEWAYS Council specifications for grades may need to be modified. geotechnical advice.
Driveways and parking areas may need to be fully supported on piers.
EARTHWORKS Retain natural contours wherever possible. Indiscriminatory bulk earthworks.
Minimise depth. Large scale cuts and benching.
CUTS Support with engineered retaining walls or batter to appropriate slope. Unsupported cuts.
Provide drainage measures and erosion control. Ignore drainage requirements
Minimise height. Loose or poorly compacted fill, which if it fails,
Strip vegetation and topsoil and key into natural slopes prior to filling. may flow a considerable distance including
Use clean fill materials and compact to engineering standards. onto property below.
FILLS Batter to appropriate slope or support with engineered retaining wall. Block natural drainage lines.
Provide surface drainage and appropriate subsurface drainage. Fill over existing vegetation and topsoil.
Include stumps, trees, vegetation, topsoil,
boulders, building rubble etc in fill.
ROCK OUTCROPS Remove or stabilise boulders which may have unacceptable risk. Disturb or undercut detached blocks or
& BOULDERS Support rock faces where necessary. boulders.
Engineer design to resist applied soil and water forces. Construct a structurally inadequate wall such as
Found on rock where practicable. sandstone flagging, brick or unreinforced
RETAINING
Provide subsurface drainage within wall backfill and surface drainage on slope blockwork.
WALLS
above. Lack of subsurface drains and weepholes.
Construct wall as soon as possible after cut/fill operation.
Found within rock where practicable. Found on topsoil, loose fill, detached boulders
Use rows of piers or strip footings oriented up and down slope. or undercut cliffs.
FOOTINGS
Design for lateral creep pressures if necessary.
Backfill footing excavations to exclude ingress of surface water.
Engineer designed.
Support on piers to rock where practicable.
SWIMMING POOLS Provide with under-drainage and gravity drain outlet where practicable.
Design for high soil pressures which may develop on uphill side whilst there
may be little or no lateral support on downhill side.
DRAINAGE
Provide at tops of cut and fill slopes. Discharge at top of fills and cuts.
Discharge to street drainage or natural water courses. Allow water to pond on bench areas.
SURFACE Provide general falls to prevent blockage by siltation and incorporate silt traps.
Line to minimise infiltration and make flexible where possible.
Special structures to dissipate energy at changes of slope and/or direction.
Provide filter around subsurface drain. Discharge roof runoff into absorption trenches.
Provide drain behind retaining walls.
SUBSURFACE
Use flexible pipelines with access for maintenance.
Prevent inflow of surface water.
Usually requires pump-out or mains sewer systems; absorption trenches may Discharge sullage directly onto and into slopes.
SEPTIC &
be possible in some areas if risk is acceptable. Use absorption trenches without consideration
SULLAGE
Storage tanks should be water-tight and adequately founded. of landslide risk.
EROSION Control erosion as this may lead to instability. Failure to observe earthworks and drainage
CONTROL & Revegetate cleared area. recommendations when landscaping.
LANDSCAPING
DRAWINGS AND SITE VISITS DURING CONSTRUCTION
DRAWINGS Building Application drawings should be viewed by geotechnical consultant
SITE VISITS Site Visits by consultant may be appropriate during construction/
INSPECTION AND MAINTENANCE BY OWNER
OWNER’S Clean drainage systems; repair broken joints in drains and leaks in supply
RESPONSIBILITY pipes.
Where structural distress is evident see advice.
If seepage observed, determine causes or seek advice on consequences.
Australian Geomechanics Vol 42 No 1 March 2007 113
Form No. 68029 RL2 August 2010
Page 28
PRACTICE NOTE GUIDELINES FOR LANDSLIDE RISK MANAGEMENT 2007
114 Australian Geomechanics Vol 42 No 1 March 2007
Form No. 68029 RL2 August 2010
Page 29
LIMITATIONS This document has been prepared for the purpose outlined in Tectonic’s proposal and no responsibility is accepted for the use of this document, in whole or in part, for any other purpose. The scope of Tectonic’s Services are as described in Tectonic’s proposal, and are subject to restrictions and limitations. Tectonic did not perform a complete assessment of all possible conditions or circumstances that may exist at the site referenced in the report. If a service is not expressly indicated, do not assume it has been provided. If a matter is not addressed, do not assume that any determination has been made by Tectonic in regards to it. Conditions may exist which were undetectable given that economic and time constraints limit the practical extent of geotechnical investigation. Variations in conditions may occur between investigation locations, and there may be special conditions pertaining to the site which have not been revealed by the investigation and which have not therefore been taken into account in the document. Where variations exist on site, additional studies and actions may be required. Tectonic’s opinions are based upon information that existed at the time that the work was performed. The passage of time, man-made or natural events, may alter the site conditions. It is understood that the Services undertaken allowed Tectonic to form an opinion of the actual conditions of the site at the time the site was visited and cannot be used to assess the effect of any subsequent changes in the quality of the site, or its surroundings, or any laws or regulations. Any assessments made in the preparation of this document are based on the conditions indicated from published sources and the findings of the investigation described. Actual subsurface conditions may differ from those indicated in the document (e.g. between boreholes or test pits). No warranty is included, either express or implied, that the actual conditions will conform exactly to the assessments contained in this document. Where data supplied by the client or other external sources, including previous site investigation data, have been used, it has been assumed that the information is correct unless otherwise stated. No responsibility is accepted by Tectonic for incomplete or inaccurate data supplied by others. This document is provided for the sole use by the Client and its professional advisers. No responsibility whatsoever for the contents of this document will be accepted to any person other than the Client. Any use which a third party makes of this document, or any reliance on or decisions to be made based on it, is the responsibility of such third parties. Tectonic accepts no responsibility for damages, if any, suffered by any third party as a result of decisions made or actions based on this document. Rev 1 (March 2016)