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Soils report for footings and effluent southern cabins
Geotechnical Soils
'Digging up all the Details'
ABN: 15 895 975 485
Soil Investigation Summary
Client Christian Hamilton-Craig Date 12/12/2021
Site Address Lot 4, RP 852013, #53 Martins Rd, Cooroy 4563 Job No SER 2530
Purpose Proposed Cabins/ Office Test Method: Vehicle Mounted Rig
Wind Category: N3 Attachments: Site Plan/Subsoil Profiles/ Photographs
(Informative AS 4055)
Reference Documents:
* Sparks Architects - Architectural Plan job no: 165, dwg: WD 3.1-10, dated:
15/9/20
* Noosa Council - Contour Overlay Plan
* Geotechnical Soils - Proposed Secondary Residence report no: SER 2184,
dated: 2/11/20
Site Details:
Description The allotment is 15.579 ha in are and of irregular shape. The details in this report
are to augment our report SER 2184 (November 2020). The SER 2184 report
addresses engineering foundation and effluent disposal parameters for the
proposed farm stay cottage to be sited in the far northeastern allotment
corner. This report reviews engineering parameter for building and effluent
application in the southeastern allotment quadrant.
The proposed structures include-:
* home office
* 2 X studio cottages
It is understood the proposed structures are to be clad and supported by pad
footings or a 'sure foot' footing system and suspended timber floor. On-site
effluent disposal required with tank water supply. Photographs attached.
Topography Contours overlain on PLATE 1/2. All proposed structures are upon a common
ridge-line. The cross fall is from the east to the west. Locally the office/ cabin is
upon a flattened crown with moderate/ steep grades extending to the
receding gully. The flank to the north grades at 1:3 (V:H). The proposed studio
cabins are on the flank that grades at 1:12 (V:H) with steeper grades on the
northern flank of 1:6/ 1:4.
Vegetation Short pasture grasses, stands of large trees to the east/ southwest and within
the receding gully head. Root networks over the land surface.
Drainage The ridge line has a cross fall to the west, with the predominate fall to the
north/ northwest. Receding gully and depression over the northern flank.
Small dam, well away. All building areas and the flank proposed for effluent
application are well drained. The access driveway is below the general land
surface.
Geology Regionally described as the Kin Kin Beds.
Typical rock types are-:
* phyllite - laminar, micaceous soft rock
* arenite - consolidated rock of sand texture
* argillite - indurated rock of siltstone / claystone
14/40 Claude Boyd Parade Office: 0413 951 991
"PRIMEX BIZ HUB" [email protected]
Bells Creek QLD 4551
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Page 2
Soil Investigation Summary
Client Christian Hamilton-Craig Date 12/12/2021
Site Address Lot 4, RP 852013, #53 Martins Rd, Cooroy 4563 Job No SER 2530
Soil Profile To establish subsoil profiles and engineering parameters within the proposed
building and effluetn application areas, five boreholes (BH) were advanced
by a small vehicle mounted drilling rig. In addition, dynamic cone
penetrometer testing was carried out adjacent selected boreholes. Test
locations shown on PLATE 1 and subsoil profiles / test values in APPENDIX A.
Homogeneous soil profiles with all clays friable and of low/ medium plasticities.
The clays are sandy and silty, with gravels insitu clays at depth. Below depths
of 1.2- 2.0 metres within the proposed building areas are interbedded
extremely weathered rock. These soil types have soil properties. At BH 4/5
(effluent application) a granular argillite rock was noted at 1.6 metres. The
rock has clays insitu and will have soil properties. Moderate and moderate/
good soil consistencies.
Discussion Building construction should consider-:
/ Remarks
- topographic setting
- proximity of large trees with intrusive root system (refer AS 2870 APPENDIX H -
Guide to the Design of Footings for Trees)
- steep grades above the receding gully
- light clays (friable)
- moderate soil consistencies
- weak rock in a clay / gravel matrix
- refer to APPENDIX B 'Examples of Good Hillside Construction'
- increased risk of landslip activity above receding gully heads where
inappropriate earthworks and insufficient drainage controls measures are
employed
Laboratory Data: Database values for the (CL) medium plasitic silty CLAYS are -:
- Plasticity Index 20%
- Linear Shrinkage 9.5%
- Estimated Instability Index 0.8%
Site Classification: In accordance with AS 2870 and based on clay reactivity, the characteristic
(AS 2870-2011) surface movement (Ys) calculates to range 20 -25 mm or 'M'.
Estimated Cut N/A m
Estimated Fill N/A m
Site Scrape Only Yes
Piers N/A m
Removal of Trees No
14/40 Claude Boyd Parade Office: 0413 951 991
"PRIMEX BIZ HUB" [email protected]
Bells Creek QLD 4551
Page 3
Soil Investigation Summary
Client Christian Hamilton-Craig Date 12/12/2021
Site Address Lot 4, RP 852013, #53 Martins Rd, Cooroy 4563 Job No SER 2530
Design Effluent On-site effluent disposal required with tank water supply. The proposed office
Remarks: and two studio cabins (east to west). Further to the west, the ridgeline
broadens to a planar flank. It is understood an AES (advanced Enviroseptic
system) is proposed for effluent disposal.
All three proposed structures could link to a common effluent disposal network
and disperse by gravity.
Design effluent loadings of -:
* office/cabin - 120 litres per day
* studio cabin - 2 persons/ 120 litres per person per day
resulting in a probable total loading of 600 litres/ day. The flank proposed for
effluent land application is represented by the soil category of 4/5 - clay
loam/ light clay. Detailed design report to follow, by others.
14/40 Claude Boyd Parade Office: 0413 951 991
"PRIMEX BIZ HUB" [email protected]
Bells Creek QLD 4551
Page 4
Figure 1 Studio Cabin area
Figure 2 Receding depression
Geotechnical Soils Pty Ltd
ABN: 15 895 975 485
Sunshine Coast, Queensland
Office: 0413 951 991
[email protected]
www.geotechnicalsoils.com.au
Page 5
Figure 3 Effluent application area
Figure 4 Receding gully
Geotechnical Soils Pty Ltd
ABN: 15 895 975 485
Sunshine Coast, Queensland
Office: 0413 951 991
[email protected]
www.geotechnicalsoils.com.au
Page 6
Figure 5 Ridge Line (east to west)
Figure 6 Office/ Cabin area
Geotechnical Soils Pty Ltd
ABN: 15 895 975 485
Sunshine Coast, Queensland
Office: 0413 951 991
[email protected]
www.geotechnicalsoils.com.au
Page 7
Figure 7 Driveway/ Frontage
Geotechnical Soils Pty Ltd
ABN: 15 895 975 485
Sunshine Coast, Queensland
Office: 0413 951 991
[email protected]
www.geotechnicalsoils.com.au
Page 8
APPENDIX A Sub Soil Profiles [OCR of page images] APPENDIX A Sub Soil Profiles
Page 9
Soil Investigation Summary
Client Christian Hamilton-Craig Date 12/12/2021
Site Address Lot 4, RP 852013, #53 Martins Rd, Cooroy 4563 Job No SER 2530
Test No. 1
Location OFFICE/ CABIN - see PLATE 1 Test Values (per 100mm)
Procedure:AS 1289.6.3.2/3-1997
Depth Origin Description (Unified Classification) Symbol Comments
0.1 2 2.1
200 Clayey SAND fine sands, dark grey brown, with silt, moist, loose. SC
0.2 1 2.2
750 Silty CLAY medium plasticity, light brown/ red brown, some fine CL (friable)
sand, trace fine gravel, moist, stiff. 0.3 1 2.3
1050 Silty CLAY low-medium plasticity, orange brown, with fine sand, CL (friable) 0.4 2 2.4
trace fine gravel, moist, very stiff. 0.5 2 2.5
1500 Sandy CLAY low-medium plasticity, yellow/ yellow brown/ CL 0.6 2 2.6
orange, fine-medium sands, with silt, some fine gravel, moist,
very stiff/hard. 0.7 3 2.7
2500 Sandy CLAY low plasticity, yellow brown/ light yellow, fine-coarse CL/XW END 0.8 2 2.8
sands, with silt, some fine-medium gravel, interbedded with (XW)
0.9 2 2.9
ROCK, moist, hard.
1.0 2 3.0
1.1 4 3.1
1.2 5 3.2
1.3 6 3.3
1.4 7 3.4
1.5 3.5
1.6 3.6
1.7 3.7
1.8 3.8
1.9 3.9
2.0 4.0
Test No. 2
Location STUDIO CABIN - see PLATE 1 Test Values (per 100mm)
Procedure:AS 1289.6.3.2/3-1997
Depth Origin Description (Unified Classification) Symbol Comments
0.1 1 2.1
100 Silty CLAY low plasticity, dark brown/ dark grey with brown, with CL
fine-coarse sand, moist, firm. 0.2 1 2.2
500 Sandy CLAY low-medium plasticity, light brown/ red orange CL (friable) 0.3 1 2.3
brown, fine-medium sands, with silt, some fine-coarse gravel, 0.4 3 2.4
moist, firm/stiff.
0.5 2 2.5
1200 Sandy CLAY low plasticity, maroon/ light grey / white, fine sands, CL
with silt, trace fine gravel, moist, stiff/very stiff. 0.6 2 2.6
2100 Sandy CLAY low plasticity, yellow/ yellow brown, fine-coarse CL/XW 0.7 4 2.7
sands, some fine gravel, interbedded with (XW) ROCK, moist, 0.8 3 2.8
very stiff/hard.
0.9 3 2.9
2500 Clayey GRAVEL fine-medium gravel, orange yellow brown, with GC/XW END
fine-coarse sand, interbedded with (XW) ROCK, moist, 1.0 6 3.0
dense/very dense.
1.1 11 3.1
1.2 3.2
1.3 3.3
1.4 3.4
1.5 3.5
1.6 3.6
1.7 3.7
1.8 3.8
1.9 3.9
2.0 4.0
14/40 Claude Boyd Parade Office: 0413 951 991
"PRIMEX BIZ HUB" [email protected]
Bells Creek QLD 4551
Page 10
Soil Investigation Summary
Client Christian Hamilton-Craig Date 12/12/2021
Site Address Lot 4, RP 852013, #53 Martins Rd, Cooroy 4563 Job No SER 2530
Test No. 3
Location STUDIO CABIN - see PLATE 1 Test Values (per 100mm)
Procedure:AS 1289.6.3.2/3-1997
Depth Origin Description (Unified Classification) Symbol Comments
0.1 1 2.1
100 Sandy CLAY low plasticity, light brown/ grey yellow brown, fine- CL
medium sands, with silt, moist, firm. 0.2 1 2.2
400 Sandy CLAY low-medium plasticity, light brown/ orange yellow CL 0.3 2 2.3
brown, fine-medium sands, with silt, trace fine gravel, moist, 0.4 1 2.4
firm/stiff.
0.5 2 2.5
1200 Silty CLAY medium plasticity, orange brown/ orange yellow/ CL (friable)
yellow, with fine sand, trace fine gravel, moist, stiff/very stiff. 0.6 3 2.6
2000 Gravely CLAY low plasticity, yellow brown/ orange yellow, fine- CL (quartz gravel) 0.7 4 2.7
medium gravel, with fine-coarse sand, moist, very stiff. 0.8 3 2.8
2500 Sandy CLAY yellow/yellow brown, fine-coarse sands, with silt, CL/XW END
0.9 4 2.9
some fine gravel, interbedded with (XW) ROCK, moist, hard.
1.0 5 3.0
1.1 8 3.1
1.2 12 3.2
1.3 3.3
1.4 3.4
1.5 3.5
1.6 3.6
1.7 3.7
1.8 3.8
1.9 3.9
2.0 4.0
Test No. 4
Location EFFLUENT - see PLATE 1 Test Values (per 100mm)
Procedure:AS 1289.6.3.2/3-1997
Depth Origin Description (Unified Classification) Symbol Comments Effluent Soil Cat.
0.1 2.1
100 Clayey SAND fine sands, light brown/ brown, SC 3 - Massive
with silt, moist, loose. 0.2 2.2
350 Silty CLAY low-medium plasticity, light brown/ CL 5 - Strongly 0.3 2.3
yellow brown, with fine sand, moist, firm. 0.4 2.4
1350 Silty CLAY low-medium plasticity, orange CL 5 - Strongly 0.5 2.5
yellow/ red brown, with fine sand, trace fine
gravel, moist, stiff/very stiff. 0.6 2.6
1600 Sandy CLAY low plasticity, yellow/ yellow CL 4 - Moderately 0.7 2.7
brown, fine-medium sands, with silt, some 0.8 2.8
fine gravel, moist, very stiff/hard.
2000 ROCK - ARGILLITE extremely weathered, XW END 4 - Massive
0.9 2.9
yellow brown/ grey yellow, lenses of (CL) 1.0 3.0
gravelly CLAY, slightly moist/moist, very low
1.1 3.1
strength.
1.2 3.2
1.3 3.3
1.4 3.4
1.5 3.5
1.6 3.6
1.7 3.7
1.8 3.8
1.9 3.9
2.0 4.0
14/40 Claude Boyd Parade Office: 0413 951 991
"PRIMEX BIZ HUB" [email protected]
Bells Creek QLD 4551
Page 11
Soil Investigation Summary
Client Christian Hamilton-Craig Date 12/12/2021
Site Address Lot 4, RP 852013, #53 Martins Rd, Cooroy 4563 Job No SER 2530
Test No. 5
Location EFFLUENT - see PLATE 1 Test Values (per 100mm)
Procedure:AS 1289.6.3.2/3-1997
Depth Origin Description (Unified Classification) Symbol Comments Effluent Soil Cat.
0.1 2.1
200 Clayey SAND fine-coarse sands, brown/ grey SC 3 - Massive
brown, with silt, some fine gravel, moist, loose. 0.2 2.2
500 Sandy CLAY low plasticity, light brown/ yellow CL 4 - Moderately 0.3 2.3
brown, fine-coarse sands, some fine 0.4 2.4
gravel/silt, moist, firm.
0.5 2.5
1600 Silty CLAY low-medium plasticity, yellow / CL 5 - Strongly
yellow brown, with fine sand, trace fine gravel, 0.6 2.6
moist, stiff/very stiff. 0.7 2.7
2000 ROCK - ARGILLITE extremely weathered, GC/XW END 4 - Massive 0.8 2.8
yellow/ yellow brown, interbedded with (GC)
clayey GRAVEL, moist, very low strength. 0.9 2.9
1.0 3.0
1.1 3.1
1.2 3.2
1.3 3.3
1.4 3.4
1.5 3.5
1.6 3.6
1.7 3.7
1.8 3.8
1.9 3.9
2.0 4.0
14/40 Claude Boyd Parade Office: 0413 951 991
"PRIMEX BIZ HUB" [email protected]
Bells Creek QLD 4551
Page 12
Interpretations, Terms and Symbols Limitations 1. This document is supplied to a specific person for a specific purpose with the scope of review defined by the client’s requests and with reference to the relevant industry standards. 2. The details within this report are based on site and soil conditions encountered at that time. 3. Assessment methods and procedures are in accordance with the referenced standards. 4. The soil profiles presented represent that actual location and can be extrapolated to render an opinion on overall subsurface conditions within a defined area. 5. The transition between soil types and layers in both vertical and horizontal dimensions can be more gradual or abrupt than this document indicates and over time, manmade or natural events may alter the site conditions. 6. External documentation referenced which can be included: fill certification, soil profiles, laboratory test results and consolidation parameters are included with an acknowledgement and understanding that the conclusions are the responsibility of that documents author. Review Procedures AS 1289 Methods of Testing of Soils for Engineering Purposes AS 1726 Geotechnical Site Investigations AS 2870 Residential Slabs and Footings – Constructions AS 3798 Guidelines on Earthworks for Commercial and Residential Development AS 4055 Wind Loads for Housing The following glossary of terms used in the description of the prevailing soil conditions is compliant with Unified Classification System with soil profile depths recorded as the END depth of that soil type.
Page 13
D depth of that soil type.
Soil Descriptions
Description and Classification of Soils for Geotechnical Purposes: Refer to AS1726-1993 (Appendix A).
The following chart (adapted from AS1726-1993, Appendix A, Table A1) is based on the Unified Soil Classification System (USCS).
Soil Colour: Is described in the moist condition using black, white, grey, red, brown, orange, yellow, green or blue. Borderline cases can be described
as a combination of two colours, with the weaker followed by the stronger. Modifiers such as pale, dark or mottled, can be used as necessary. Where
colour consists of a primary colour with secondary mottling, it should be described as follows:
(Primary) mottled (Secondary). Refer to AS 1726-1993, A2.4 and A3.3.
USCS
Particle Group
Major Divisions Typical Names Laboratory Classification
size mm Symbol
% < 0.075 mm Plasticity of Cu= D60 Cc = (D 30)2
NOTES
(2) fine fraction D10 (D10)(D60)
BOULDERS
(more than half of material less than 63 mm is larger than 0.075mm)
200
COBBLES
63 Well graded gravels and
Between 1
GW gravel-sand mixtures, little or 0-5 >4 (1) Identify fines by
and 3
no fines
Use the gradation curve of material passing 63 mm for classification of fractions according to the criteria given in 'Major Divisions'
the method given
for fine-grained
Poorly graded gravels and
Fails to comply with soils.
GP gravel-sand mixtures, little or 0-5
COARSE GRAINED SOILS
GRAVELS coarse above
no fines, uniform gravels
(more than 20
half of Silty gravels, gravel-sand-silt Below 'A'
GM 12-50
mixtures (1) line or PI<4
coarse medium
fraction is Above 'A' line
Clayey gravels, gravel-sand
GC 12-50 and (2) Borderline
larger than 6 clay mixtures (1)
PI>7 classifications
2.36 mm) fine occur when the
Well graded sands and
2.36 Between 1 percentage of
SW gravelly sands, little or no 0-5 >6
and 3 fines (fraction
fines
SANDS smaller than
Poorly graded sands and
Fails to comply with 0.075 mm size)
(more than SP gravelly sands, little or no 0-5
coarse above is greater than
half of coarse fines
0.6 5% and less than
fraction is 12%. Borderline
Silty sands, sand silt mixtures Below 'A'
smaller than SM 12-50 classifications
(1) line or PI<4
2.36 mm) medium require the use
0.2 Above 'A' line of SP-SM,
Clayey sands, sand-clay
fine 0.075 SC 12-50 and GWGC.
mixtures (1)
PI>7
Inorganic silts, very fine
sands, rock flour, silty or
ML
(more than half of material less than 63 mm is smaller than 0.075 mm)
clayey fine sands or clayey
SILTS & CLAYS silts with slight plasticity
(Liquid Limit ≤50%)
Inorganic clays of low to
medium plasticity, gravelly
CL CI
clays, sandy clays, silty clays,
lean clays
FINE GRAINED SOILS
Organic silts and clays of low
OL
plasticity
Inorganic silts, mic- aceous
MH or diato-maceous fine sands
or silts, elastic silts
Inorganic clays of high
CH
SILTS & CLAYS plasticity, fat clays
(Liquid Limit >50%)
Organic silts and clays of high
OH
plasticity
HIGHLY ORGANIC Peat and other highly organic
PT
SOILS soils
Soil Moisture Condition: Is based on the appearance and feel of soil. Refer to AS 1726-1993, A2.5.
Page 14
Term Description
Cohesive soils; hard and friable or powdery, well dry of plastic limit.
Dry
Granular soils; cohesionless and free-running
Soil feels cool, darkened in colour.
Moist Cohesive soils can be moulded.
Granular soils tend to cohere.
Soil feels cool, darkened in colour.
Wet Cohesive soils usually weakened and free water forms on hands when handling.
Granular soils tend to cohere and free water forms on hands when handling.
Consistency of Cohesive Soils: May be estimated using simple field tests, or described in terms of a strength scale. In the field, the undrained shear
strength (su) can be assessed using a simple field tool appropriate for cohesive soils, in conjunction with the relevant calibration. Refer to AS 1726-1993,
Table A4.
Consistency - Essentially Cohesive Soils Soil Particle Sizes
SPT Undrained Unconfined
Shear Compressive
Term Field Guide Symbol “N” Term Size Range
Strength Strength
Value su (kPa) qu (kPa)
Oozes between fingers BOULDERS >200 mm
Very soft when squeezed in hand. VS 0-2 <12 <25 COBBLES 63-200 mm
Coarse GRAVEL 20-63 mm
Easily moulded with
Soft fingers. S 2-4 12-25 25-50 Medium GRAVEL 6-20 mm
Fine GRAVEL 2.36-6 mm
Can be moulded by strong Coarse SAND 0.6-2.36 mm
Firm pressure of fingers. F 4-8 25-50 50-100 Medium SAND 0.2-0.6 mm
Fine SAND 0.075-0.2 mm
Stiff St 8-15 50-100 100-200 SILT 0.002-0.075 mm
CLAY <0.002 mm
Not possible to mould with
Very stiff fingers. VSt 15-30 100-200 200-400
Can be indented with
Hard difficulty by thumb nail. H >30 >200 >400
Note: SPT - N to qu correlation from Terzaghi and Peck, 1967. (General guide only).
Consistency of Non-Cohesive Soils: Is described in terms of the density index, as defined in AS 1289.0-2000. This can be assessed using a field tool
appropriate for non-cohesive soils, in conjunction with the relevant calibration. Refer to AS 1726-1993, Table A5; BS5930-1999, p117.
Consistency - Essentially Non-Cohesive Soils
Term Symbol SPT N Value Field Guide Density Index (%)
Very loose VL 0-4 Foot imprints readily 0-15
Loose L 4-10 Shovels Easily 15-35
Medium dense MD 10-30 Shovelling difficult 35-65
Dense D 30-50 Pick required 65-85
Very dense VD >50 Picking difficult 85-100
Standard Penetration Test (SPT): Refer to. AS 1289.6.3.1-2004. Example report formats for SPT results are shown below:
Test Report Penetration Resistance (N) Explanation / Comment
4, 7, 11 N=18 Full penetration; N is reported on engineering borehole log
18, 27, 32 N=59 Full penetration; N is reported on engineering borehole log
4, 18, 30/15 mm N is not reported 30 blows causes less than 100 mm penetration (3rd interval) – test discontinued
30/80 mm N is not reported 30 blows causes less than 100 mm penetration (1st interval) – test discontinued
rw N<1 Rod weight only causes full penetration
hw N<1 Hammer and rod weight only causes full penetration
hb N is not reported Hammer bouncing for 5 consecutive blows with no measurable penetration – test
discontinued
Page 15
Rock Descriptions
Refer to AS 1726-1993 (Appendix A3.3) for the description and classification of rock material composition, including:
(a) Rock type (Table A6, (a) and (b))
(b) Grain size
(c) Texture and fabric
(d) Colour (describe as per soil).
The condition of a rock material refers to its weathering characteristics, strength characteristics and rock mass properties. Refer to AS 17261993
(Appendix A3 Tables A8, A9 and A10).
Weathering Condition (Degree of Weathering):
The degree of weathering is a continuum from fresh rock to soil. Boundaries between weathering grades may be abrupt or gradational.
Rock Material Weathering Classification
Weathering Grade Symbol Definition
Soil-like material developed on extremely weathered rock; the mass structure and substance fabric are no
Residual Soil RS
longer evident; there is a large change in volume but the material has not been significantly transported.
Extremely Weathered Rock is weathered to such an extent that it has 'soil' properties, i.e. it either disintegrates or can be remoulded
XW
Rock in water, but substance fabric and rock structure still recognisable.
Strong discolouration is evident throughout the rock mass, often with significant change in the constituent
Highly Weathered Rock HW
minerals. The intact rock strength is generally much weaker than that of the fresh rock.
Moderately Weathered Modest discolouration is evident throughout the rock fabric, often with some change in the constituent minerals.
MW
Rock The intact rock strength is usually noticeably weaker than that of the fresh rock.
Slightly Weathered Rock SW Rock is slightly discoloured but shows little or no change of strength from fresh rock.
Fresh Rock FR Rock shows no sign of decomposition or staining.
Notes:
1. Minor variations within broader weathering grade zones will be noted on the engineering borehole logs.
2. Extremely weathered rock is described in terms of soil engineering properties.
3. Weathering may be pervasive throughout the rock mass, or may penetrate inwards from discontinuities to some extent.
4. The ‘Distinctly Weathered (DW)’ class as defined in AS 1726-1993 is divided to incorporate HW and MW in the above table. The symbol DW should
not be used.
Strength Condition (Intact Rock Strength):
Strength of Rock Material
(Based on Point Load Strength Index, corrected to 50 mm diameter – Is(50). Field guide used if no tests available. Refer to AS 4133.4.1-2007.
Point Load
Term Symbol Index (MPa) Field Guide to Strength
Is(50)
Extremely Low EL ≤0.03 Easily remoulded by hand to a material with soil properties.
Material crumbles under firm blows with sharp end of pick; can be peeled with knife; too hard
Very Low VL >0.03 ≤0.1
to cut a triaxial sample by hand. Pieces up to 3 cm thick can be broken by finger pressure.
Easily scored with a knife; indentations 1 mm to 3 mm show in the specimen with firm blows
of the pick point; has dull sound under hammer. A piece of core 150 mm long by 50 mm
Low L >0.1 ≤0.3
diameter may be broken by hand. Sharp edges of core may be friable and break during
handling.
Readily scored with a knife; a piece of core 150 mm long by 50 mm diameter can be broken
Medium M >0.3 ≤1.0
by hand with difficulty.
A piece of core 150 mm long by 50 mm diameter cannot be broken by hand but can be broken
High H >1 ≤3
by a pick with a single firm blow; rock rings under hammer.
Very High VH >3 ≤10 Hand specimen breaks with pick after more than one blow; rock rings under hammer.
Specimen requires many blows with geological pick to break through intact material; rock rings
Extremely High EH >10
under hammer.
Notes:
1. These terms refer to the strength of the rock material and not to the strength of the rock mass which may be considerably weaker due to the effect of
rock defects.
2. Anisotropy of rock material samples may affect the field assessment of strength.
Page 16
APPENDIX B
Examples of Good Hillside
Contruction
[OCR of page images]
APPENDIX B
Examples of Good Hillside
Contruction
Page 17
AUSTRALIAN GEOGUIDE LR8 (CONSTRUCTION PRACTICE)
HILLSIDE CONSTRUCTION PRACTICE
Sensible development practices are required when building on hillsides, particularly if the hillside has more than a low risk of instability
(GeoGuide LR7). Only building techniques intended to maintain, or reduce, the overall level of landslide risk should be considered.
Examples of good hillside construction practice are illustrated below.
WHY ARE THESE PRACTICES GOOD?
Roadways and parking areas - are paved and incorporate kerbs which prevent water discharging straight into the hillside (GeoGuide
LR5).
Cuttings - are supported by retaining walls (GeoGuide LR6).
Retaining walls - are engineer designed to withstand the lateral earth pressures and surcharges expected, and include drains to prevent
water pressures developing in the backfill. Where the ground slopes steeply down towards the high side of a retaining wall, the disturbing
force (see GeoGuide LR6) can be two or more times that in level ground. Retaining walls must be designed taking these forces into
account.
Sewage - whether treated or not is either taken away in pipes or contained in properly founded tanks so it cannot soak into the ground.
Surface water - from roofs and other hard surfaces is piped away to a suitable discharge point rather than being allowed to infiltrate into
the ground. Preferably, the discharge point will be in a natural creek where ground water exits, rather than enters, the ground. Shallow,
lined, drains on the surface can fulfil the same purpose (GeoGuide LR5).
Surface loads - are minimised. No fill embankments have been built. The house is a lightweight structure. Foundation loads have been
taken down below the level at which a landslide is likely to occur and, preferably, to rock. This sort of construction is probably not
applicable to soil slopes (GeoGuide LR3). If you are uncertain whether your site has rock near the surface, or is essentially a soil slope,
you should engage a geotechnical practitioner to find out.
Flexible structures - have been used because they can tolerate a certain amount of movement with minimal signs of distress and
maintain their functionality.
Vegetation clearance - on soil slopes has been kept to a reasonable minimum. Trees, and to a lesser extent smaller vegetation, take
large quantities of water out of the ground every day. This lowers the ground water table, which in turn helps to maintain the stability of
the slope. Large scale clearing can result in a rise in water table with a consequent increase in the likelihood of a landslide (GeoGuide
LR5). An exception may have to be made to this rule on steep rock slopes where trees have little effect on the water table, but their
roots pose a landslide hazard by dislodging boulders.
Possible effects of ignoring good construction practices are illustrated on page 2. Unfortunately, these poor construction practices are
not as unusual as you might think and are often chosen because, on the face of it, they will save the developer, or owner, money. You
should not lose sight of the fact that the cost and anguish associated with any one of the disasters illustrated, is likely to more than wipe
out any apparent savings at the outset.
ADOPT GOOD PRACTICE ON HILLSIDE SITES
Australian Geomechanics Vol 42 No 1 March 2007
Page 18
AUSTRALIAN GEOGUIDE LR8 (CONSTRUCTION PRACTICE)
WHY ARE THESE PRACTICES POOR?
Roadways and parking areas - are unsurfaced and lack proper table drains (gutters) causing surface water to pond and soak into the
ground.
Cut and fill - has been used to balance earthworks quantities and level the site leaving unstable cut faces and added large surface loads
to the ground. Failure to compact the fill properly has led to settlement, which will probably continue for several years after completion.
The house and pool have been built on the fill and have settled with it and cracked. Leakage from the cracked pool and the applied
surface loads from the fill have combined to cause landslides.
Retaining walls - have been avoided, to minimise cost, and hand placed rock walls used instead. Without applying engineering design
principles, the walls have failed to provide the required support to the ground and have failed, creating a very dangerous situation.
A heavy, rigid, house - has been built on shallow, conventional, footings. Not only has the brickwork cracked because of the resulting
ground movements, but it has also become involved in a man-made landslide.
Soak-away drainage - has been used for sewage and surface water run-off from roofs and pavements. This water soaks into the ground
and raises the water table (GeoGuide LR5). Subsoil drains that run along the contours should be avoided for the same reason. If felt
necessary, subsoil drains should run steeply downhill in a chevron, or herring bone, pattern. This may conflict with the requirements for
effluent and surface water disposal (GeoGuide LR9) and if so, you will need to seek professional advice.
Rock debris - from landslides higher up on the slope seems likely to pass through the site. Such locations are often referred to by
geotechnical practitioners as "debris flow paths". Rock is normally even denser than ordinary fill, so even quite modest boulders are
likely to weigh many tonnes and do a lot of damage once they start to roll. Boulders have been known to travel hundreds of metres
downhill leaving behind a trail of destruction.
Vegetation - has been completely cleared, leading to a possible rise in the water table and increased landslide risk (GeoGuide LR5).
DON'T CUT CORNERS ON HILLSIDE SITES - OBTAIN ADVICE FROM A GEOTECHNICAL PRACTITIONER
More information relevant to your particular situation may be found in other Australian GeoGuides:
• GeoGuide LR1 - Introduction • GeoGuide LR6 - Retaining Walls
• GeoGuide LR2 - Landslides • GeoGuide LR7 - Landslide Risk
GeoGuide LR3 - Landslides in Soil • GeoGuide LR9 - Effluent & Surface Water Disposal
•
GeoGuide LR4 - Landslides in Rock GeoGuide LR10 - Coastal Landslides
•
GeoGuide LR5 - Water & Drainage • GeoGuide LR11 - Record Keeping
The Australian GeoGuides (LR series) are a set of publications intended for property owners; local councils; planning authorities;
developers; insurers; lawyers and, in fact, anyone who lives with, or has an interest in, a natural or engineered slope, a cutting, or an
excavation. They are intended to help you understand why slopes and retaining structures can be a hazard and what can be done with
appropriate professional advice and local council approval (if required) to remove, reduce, or minimise the risk they represent. The
GeoGuides have been prepared by the Australian Geomechanics Society, a specialist technical society within Engineers Australia, the
national peak body for all engineering disciplines in Australia, whose members are professional geotechnical engineers and engineering
geologists with a particular interest in ground engineering. The GeoGuides have been funded under the Australian governments’ National
Disaster Mitigation Program.
Australian Geomechanics Vol 42 No 1 March 2007
Page 19
PLATE 1 Test Locations [OCR of page images] PLATE 1 Test Locations
Page 20
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PLATE 2 Council Contour Plan [OCR of page images] PLATE 2 Council Contour Plan
Page 22
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