Information response - GEOTECH REPORT

Page 2

 

“Me
Ger) ve
ws Be

CONSULTING

 

GEOTECHNICAL REVIEW

1. INTRODUCTION

iv Under the instructions of Phil Broad, GeoConsulting have undertaken a geotechnical stability
review for the proposed residence on #528, Lot 5 (RP227335) Black Mountain 5-Co.
1.2 The purposes of the investigation were to: ~

@ Review existing report documents;

  
 

@° Establish soil parameters/conduct a site walkover/advanced a reference berehole;.-—
+ Comment upon the geotechnical aspects of the allotment in regarddto slope instabilityand in

accordance with the objectives presented in Sunshine Coast Regiona Council; “Slope and
Geological Stability” Policy.

1.3 Review procedures were in accordance with the following: -
AS1289 ~ Methods of testing of soils for engineering purposes
@ ASI726— = - Geotechnical Site Investigations
@ AS2870 - Residential slabs and footings - Construction
@ AS379B- = Guidelines on earthworks for commercial and residential development

1.4 Existing documents referenced in this review include: -

¢ Site Investigation Report, Lot 5 Black Mountain Road, Cooroy, job no. 28955-COR, 24"
January 2011 by Heltech Industries;

¢ Effluent Disposal Report, Lot 5 Black Mountain Road, Cooroy, job no. 11/0067, 16" February
2011 by Global Testing;

«@ Extract of Building Plans by Coral Homes, sheets 1A and 3, Lot 5 Black Mountain Road,
Cooroy;

¢ “Landslide Risk Management Concepts and Guidelines”, March 2000 by Australian
Geomechanics Society;

¢ Landslip and Flooding Map OMS5.3, Sunshine Coast Regional Council (see PLATE 2
attached).

1.5 Methodology - Mathematical analysis of stability has its uses and limitations. For example
topographic, soil and groundwater conditions are site specific and may not accurately correlate even
over short distances. On slopes that are unfailed it therefore becomes difficult to predict where failure
planes may exist and balancing this with anticipated groundwater levels.

The stability review technique employed in this study is to empirically relate observed landslip
occurrences with combinations of topography, geology and soil profile and groundwater conditions.

 

Office at: 1/8 Denna St, Maroochydore, Q, 4558,
Phone: 5443 6622, Fax: 5479 1899, Email: [email protected]

Page 3

Report: 15960, May 11 Page 2

Numerous studies into the causes of landslides within southeast Queensland comment upon an
equilibrium existing between weathering of the underlying rock and removal of the soil mantle. Where
landslides are known to occur it can be concluded that some change to this equilibrium has occurred.
The key factor in maintenance of this equilibrium is water; whether that is infiltration reducing soils
shear strength and/or an increase in pore (groundwater) pressure.

Typically the removal of natural forest will reduce transpiration by trees and hence during high rainfall
events allow increased pore (groundwater) pressures. Additionally with tree removal there is a
diminished binding of the upper soils by root systems.

1.6 Our initial review included:
# Maroochy Shire Council “Landslip Hazard Mapping”- which identifies the allotment to
include both hazard and non-hazard areas;
Review of regional geotechnical mapping;
“Landslide Risk Management Concepts and Guidelines”, March 2000 by Australian
Geomechanics Society;
4 Review referenced soil investigation and effluent disposal reports.

2. PHYSIOGRAPHY

2.1 Land Description
Residential allotment regionally located over dissected topography to the west of Cooroy township. The

area is represented by narrow ridges, spurs and deep intervening gullies. The allotment is(Qng in area
and locally is accessed by Sie “cannon Pgs off Black Mountain Road.

2.2 Vegetation

“ Medium/long pasture grasses and numerous srhali/medium treéon the lower flank, Some recent tree
enn .

removal was evident, Refer to site photographs.

 

(i

2.3 Crossfall

Locally the allotment includes a narrow crown with flanks grading to the east. The proposed residential
area incorporates the crown and near flank. Contours supplied indicate a relative fall of 1.5 metres over the
house area, with typical grades of 1:5 (V:H). Area to the southeast of the building area is locally flatter
while the northeastern flank steepens to 1:3.

2.4 Drainage
The building area is well drained with the flanks of planar shape.

2.5 Regional Geology - Regional geology describes this allotment to be upon the Kin Kin Beds.
Typical rock types include phyllite, shale, arenite and argillite. All these rock types contain fine grained
sediments and can be micaceous. Locally quartz bands will be encountered. Rock is bedded and visually
evident in surrounding road embankments.

 

Office at: 1/8 Denna St, Maroochydore, Q, 4558.
Phone: 5443 6622, Fax: 5479 1899, Email: [email protected]

Page 4

Report: 15960, May 11 Page 3

2.6 To investigate subsoil details a single borehole was advanced by a small vehicle mounted
drilling tig and existing documents were reviewed. To augment the borehole, a dynamic cone
penetrometer test was advanced to assess soil strengths. Subsoil profiles are presented in APPENDIX A
‘with test locations shown on PLATE 1.

2.7 Boreholes revealed a residual clay profile. All clays were friable in structure, micaceous in
texture and ranged from low to medium/high plasticity values. Database tecords indicate these clays to
be moderately reactive and the Heltech Industries report concludes an Iss of 1.8. A weathered phyllite
rock within a clay matrix was noted below 1.2 metres. This soil structure continued to at least 3.0
metres. Similar soil profiles were recorded in the Heltech Industries report.
(8 Groundwater - No seepage or groundwater were noted with our fieldwork carried out
\cubSequent to a rainfall event.

2.9 Surface Movement - In accordance with AS2870 “Residential Footings and Slabs”, the Heltech
Industries report concludes an expected surface movement (Y,) ranging 45-50mm.,

2.10 General Definitions of Site Classes

 

Class Foundation Surface Movement

 

A Most sand and rock sites with little or no ground movement NIA
from moisture changes.

 

 

S Slightly reactive clay sites* with only slight ground movement.| 0mm <Ys £20 mm
from moisture changes.
M Moderately reactive clay or silt sites, which can experience | 20 mm < Ys £40 mm

moderate ground movement from moisture changes.

 

H Highly reactive clay sites, which can experience high ground | 40 mm < Ys 70mm
movement from moisture changes.

 

E Extremely reactive sites, which can experience extreme ground Ys >70 mm
movement from moisture changes.

 

P Sites which include soft soils, such as soft clay or silt or loose NIA
sands; landslip; mine subsidence; collapsing soils; soils subject
to erosion; reactive sites subject to abnormal moisture

 

 

conditions or sites which cannot be classified otherwise.

 

 

 

3. STABILITY RISK

 

3.1 In review of our detailed site walkover, document Teviewand 1 orehole investigation, we would
conclude the crown and near flank area of Lot 5 to be fa “low of brn impacting on person
or property.

 

 

Office at: 1/8 Denna St, Maroochydore, Q, 4558.
Phone: 5443 6622, Fax: 5479 1899, Email: [email protected]

Page 5

Report: 15960, May 17 Page 4

3.2 The risk classification is in accordance with Australian Geomechanics Society document
“Landslide Risk Management Concepts and Guidelines”.

Risk Level Implications
Risk Level Example Implications(.1)

VH | VERY HIGH RISK Extensive detailed investigation and research, planning
and implementation of treatment options essential to
reduce risk to acceptable levels; may be too expensive and

not practical.

 

 

 

 

H | HIGH RISK Detailed investigation, planning and implementation of
treatment options required to reduce risk to acceptable
levels.

M_ | MODERATE RISK Tolerable provided treatment plan is implemented to

maintain or reduce risks. May be accepted. May require
investigation and planning of treatment options.

 

 

 

 

 

 

Cc LOW RISK Usually accepted. Treatment requirements and
responsibility to be defined to maintain or reduce risk.
VL | VERY LOW RISK Acceptable. Manage by normal slope maintenance
procedures.

 

Note: (1) The implications for a particular situation are to be determined by all
parties to the risk assessment; these are only given as a general guide.
— We would conclude the crown area to be principally of low risk. The low risk determination recognises

the crown area is located such that geological and topographic aspects have not generally been associated
with slope instability. Appropriate construction techniques, will however maintain relative slope stabilities.

3.3 Good Engineering Practice ~ Attached as APPENDIX B, are extracts from “Landslide Risk
Management Concepts & Guidelines”, from the Australian Geomechanics Society Sub-Committee on
Landslide Risk Management:

+ “Some Guidelines for Hillside Construction”

+ “Examples of Good Hillside Practice”

 

Office at: 1/8 Denna St, Maroochydore, Q, 4558.
Phone: 5443 6622, Fax: 5479 1899, Email: [email protected]

Page 6

Report: 15960, May 11

3.4

Tn accordance with Table B1, ASI 726- 1995-Geotechniee
potential site hazard for Lot 5 (RP 227335), to’bé “Class C/Minor”

weed

Table E1

 
  
 

=1993)

Page 5

Site Investigations, we conclude that the

 

Aspect of Classification

 

Classification of Potential Hazard

 

Lok Assessment . CK
Class A Class B Ke)
Severe Significant .S~~Mino.

 

1. Risk to human life

Reasonable to anticipate
loss of life, directly
attributable to failure

Possibility of loss of life

recognized but not
expected; however
significant risk of serious
injury to persons is
appreciated

Neither loss of life nor
serious injury expected

 

2. Economic loss

 

2.1 Property damage

Expect extensive damage
to structures and

Expect appreciable
damage to structures,

Minor damage expected

 

short term disruption to
communities or to
facilities

facilities and to public and private
facilities
2.2 Indirect loss, e.g. by | Serious Appreciable Negligible

 

3. Ease of restoration

 

Project provides an
essential service,
restitution not
practicable; no short to
medium tern alternatives
available

 

 

Project provides an
essential or important
service but restitution is
practicable or alternatives
are available in short to
medium term

 

Restitution is practicable,
indirect losses due to
failure can be tolerated
until restitution is
complete

 

 

4, CONSTRUCTION RECOMMENDATIONS

4.1
Performance Criteria: -
oN

Site Clearing

> Retain natural vegetation wherever practicable.

# Not to indiscriminately clear the site

Acceptable measures: -

> Only clear the site where required for construction of the proposed residence, and retain as much of the
natural vegetation as possible. Treed vegetation will be required to be removed for bushfire safety
regulations. The general building envelope has long grasses and minor scrubby regrowth. Exposed soils
should be planted with quick growing grasses or ground cover species.

 

Office at: 1/8 Derina St, Maroochydore, Q, 4558.
Phone: 5443 6622. Fax: 5479 1899, Email: [email protected]

Page 7

Report: 15960, May (1 Page 6

4.2 Earthworks
Performance Criteria: -
¢ Retain natural contours wherever possible.
FILLING
¢ Minimise height.
¢ Strip vegetation and topsoil and key into natural slopes prior to filling.
¢ Use clean fill materials and compact to engineering standards.
Q Batter to appropriate slope or support with engineered retaining wall.
¢ Provide surface drainage and appropriate subsurface drainage.
CUTS
¢@ Minimise depth.
© Support with engineered retaining walls or batter to appropriate slope.
¢ Provide drainage measures and erosion control
ROCK OUTCROPS & BOULDERS
4 Remove or stabilise boulders, which may have unacceptable risk.
@ Support rock faces where necessary.
Acceptable measures: ~
4.2.1 General Earthworks - The proposed building area is to be stripped of all organic material
and/or material that will inhibit construction. The residence is proposed as slab on ground, therefore a cut
of around (0 metas will be required. This will result in the residential structure being part on cut
materials and part on placed fill.
The following details should be considered: -
¢ Earthworks should be prepared in accordance with the guidelines of AS3798 ~ Guidelines
on earthworks for commercial and residential developments.
¢ A positive drainage gradient is to be maintained over the building areas.
be) Spoon drains to be installed at the toe of cut embankments
Fill batters should grade at not Iess than 1:2 (V:H).
Peat batters which ate unretained should grade at not less than 1:1¥% (V:H).
¢ Exposed surfaces should be vegetated to reduce the opportunity for runoff scour
Excessive earthworks proposed on this site may require an “Operational Works” permit, which must be
obtained from the Local Authority.

4.2.2 Filling - Site preparation of filled areas will include stripping of topsoil and closely
benching the exposed slope prior to placenent-of fill in accordance with AS3798. Fill areas should be
For minor fill areas (less than 1.0 metres), the
7:2 (V: H) and vegetated immediately to reduce the

prepared to support minimum loads of at
batters should be prepared to a maximum gradé
opportunity for scour.

   

4.2.3 Retention - Cut embankments could engage weathered rock. Rigid or flexible retention
methods can be employed where necessary. A spoon drain above the cut area should remove overland
flow with suitable drainage media placed between the retention system and exposed soil. Unretained cut
embankments can grade at 1:14 {V:H)} for clays/gravels and 1:V2 (V:H) for competent rack.

 

Office at: 1/8 Denna St, Maroochydore, Q, 4558.
Phone: 5443 6622, Fax: 5479 1899, Email: [email protected]

Page 8

Report: 15960, May 11 Page 7

4.3 Drainage
Performance Criteria: -
SURFACE
Provide at tops of cut and fill slopes.
Discharge to street drainage or natural watercourses.
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.
SUBSURFACE
¢ Provide filter around subsurface drain.

*e- ¢ oe @

Provide drain behind retaining walls.
@ Use flexible pipelines with access for maintenance.
@ Prevent inflow of surface water.

Acceptable measures: - - bu od ue

Drainage over the building ayea-is-ver-gead, Wowever, subsequent to earthworks the platform would be
described as poorly drained svate rain ould be constructed at the toe of the cut batter with the
platform having a minor fall back to the cut toe. As the building area adjoins the crown there is a
minimal runoff catchment. Roof water will be collected for domestic supply. Water is not to pond in

etaround footings during or after construction. Further, the proposed floor level is not to be less than
Crs 2x the finished ground level, or as required by the relevant Local Authority.
44 Access & Driveways
Performance Criteria: -
¢ Satisfy requirements listed within for cuts, fills, retaining walls and drainage.
+ Council specifications for grades may need to be modified.
+ Driveways and parking areas may need to be fully supported on piers.
¢ Excavate and fill for site access before Geotechnical advice.
Acceptable measures: -

Driveways and areas for car turning are also to be provided in accordance with the Local Authority's
requirements. Only minor construction is required to provide a driveway access.

4.5 Retaining Walls
Performance Criteria: -
¢ Engineer designed to resist applied soil and water forces.
@ Found on rock where practicable.
4 Provide subsurface drainage within wall backfill and surface drainage on slope above.
Construct wall as soon as possible after cut/fill operation.
Acceptable measures: -
All retaining walls over 1.0 metre in height, whether stand-alone or forming part of the proposed

residence, are to be designed by a suitable qualified engincer. No details have been supplied on
proposed retaining wails. Design criteria can be referred from the soils data.

 

Office at: 1/8 Denna St, Maroochydore, Q, 4558.
Phone: 5443 6622, Fax: 5479 1899, Email: [email protected]

Page 9

Report: 15960, May 11 Page 8

4.6 Foundations
Performance Criteria: -
Found within rock where practicable.

% Use rows of piers or strip footings oriented up and down slope.

¢ Design for lateral creep pressures if necessary.

¢ Backfill footing excavations to exclude ingress of surface water.
Acceptable measures: -
All founding should be to homogeneous soil types, and based on the amount of earthworks anticipated
the founding target stratum should be the rock/clay matrix below 1.2 metres depth (refer borehole
one).

 

Office at: 1/8 Denna St, Maroochydore, Q, 4558.
Phone: 5443 6622, Fax: 5479 1899, Email: [email protected]

Page 10

Report: 15960, May 11

4.7

Septic & Sullage Disposal

Performance Criteria: -

Page 9

¢ Usually requires pump-out or mains sewer systems; absorption trenches may be possible in

some areas if risk is acceptable.

¢ Storage tanks should be watertight and adequately founded.
Acceptable measures: ~

Selecting the land-application system to fit the site and the soil:

 

 

Site or Soil System Selection Possible Installation System
Constraint Modifications to Practice Management
mitigate constraint’ ~
® Disinfection and | © Needs special © Install when soils | © Minimise

Soils with very
low
permeability
(Category 5 and
6 soils)

nutrient removal.

© Large application
area.

® Reduce flow of
wastewater using
water saving
devices, or
composting
toilets.

© Mounds, ETA
beds or trenches
or inigation
systems,
designed using
water-balance
analysis.

design.

© Prepare receiving
soil by deep
tipping, shallow
cultivation, and
applying gypsum.

* Promote formation
of biological pores
by growing
vigorous
vegetation.

© Dose effluent so as
to wet the soil
more than once per
day.

@ Place soil of good
permeability
around absorption
trenches, or around
ETA beds and
trenches.

are dry or slightly
moist.

© Avoid heavy
equipment on
application area
when soils are
moist or wet.

e Avoid smearing
sides and
bottoms of
trenches and
beds.

© Prepare surface
of soil if using
irrigation.

domestic water
use,

« Minimise
discharge of
sodium salts to
application area.

« Alternate
between
different parts of
the land
application area.

© Monitor level of
groundwater.

 

 

Steep slope

 

® Surface irrigation
unsuitable for
slopes >6%.

© The primary
criterion for
selection may be
coast {eg.
Mounds will need
much soil on
downhill side).

 

*Benching may be
feasible if soil is
reasonable stable.

®Pay special attention
lo reducing surface
infiltration (eg.
Interception drains
uphill and
tainwater-shredding
designs).

® If mound is used,
design toe to
encourage
infiltration.

 

*Trenches more
difficult to dig,
particularly for
slopes above 25%.

© Pay extra
attention to the
tisk of erosion
during
construction.

 

* Needs monitoring
of erosion and
seepage.

*Access is best
discouraged.

 

 

Office at: 1/8 Denna St, Maroochydore, Q, 4558.
Phone: 5443 6622, Fax: 5479 1899, Email: [email protected]

 

 

Page 11

Report: 15960, May 11 Page 10

4.8 Erosion Control & Landscaping
Performance Criteria: -
@ Control erosion as this may lead to instability.
«@ Revegetate cleared area.
Acceptable measures: -
Prior to construction, an erosion and sediment control plan should be established. This document can be
referenced to the publication, “Soil Erosion and Sediment Control” - The Institution of Engineers Australia.

49 Construction Recommendations
Performance criteria: -
HOUSE DESIGN:
¢ Use flexible structures, which incorporate properly, designed brickwork, timber or steel
frames, timber or panel cladding.
¢ Consider use of split-levels.
¢ Use decks for recreational areas where appropriate,
Acceptable measures: -
The residential area will be benched into the crown and near flank,

4.10 Site Maintenance

Long-term stability of the house foundations is the Tesponsibility of the owner/occupier of the
dwelling. Large changes in moisture conditions around the structure's footings (inconsistent watering
patterns), will cause movement, and may lead to damage of the house. Further, trees are to be planted
away from the structure area in order not to adversely affect the foundation performance, You are
advised to read the report, “Foundation Maintenance and Footing Performance: A Homeowner's
Guide", sheet No. 10-91, produced by Dr P.F. Walsh of the CSIRO, which can be downloaded from
http://www.publish,csiro.au/nid/22/pid/3612.htm.

5. CONCLUSION

5.1 ) Surrounding two and single storey residences are located on similar topographic and geological

units

 
 
 

5) We conclude the crown and near flank area as described will have a negligible landslip impact
risk with no significant geotechnical development constraints however building structures and filling is
excluded on slopes that exceed 1:3 (V:H).

i ) Residential development and effluent-disposal on this site should consider:
¢ Foundation site classificatidn “H” (AS2870):
Residential founding to a onion 1.2 metres below the existing ground level;
Building platform is prepared as a “controlled” fill;
Fill batters no steeper than 1:2 (V:H):
On-site effluent disposal southeast of the residence and to incorporate low volume output

e¢ ¢ + @

application methods.

 

Office at: 1/8 Denna St, Maroochydore, Q, 4558,
Phone: 5443 6622, Fax: 5479 1899, Email: [email protected]

Page 12

Report: 15960, May 11 Page 71

5.4 The details of this report are limited to a specific area with the investigation compiled for a
specific purpose and for specific persons. Inferting or extrapolating details beyond the scope of this
investigation should be avoided.

5.5 The defined building area has a low risk of slope instability, with attention to the design details
in this report the risk for the proposed residence can be maintained as low.

 

Office at: 1/8 Denna St, Maroochydore, Q, 458.
Phone: 5443 6622, Fax: 5479 1899, Email: [email protected]

Page 13

 

Semis, 1t300 (A)

  

25,75-— — ~
R800 — — ~~

6.25
22659 tN

 

 

 

 

 

 

 

 

 

 

tot, slope

“Lieneak

 

 

pps
Eoin — 4
oe BE san 50° a
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Leas a8hF
Wir
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Edge of Bltunen Drivewayea, “Pa Gp
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Page 14

Incorporating:

    

 

aamuasise
INVESTIGATIONS:

CONSULTING STRUCTURAL

PLATE 2

Extract From:-

Sunshine Coast Regional Council’s, Noosa Plan
“Mary River Catchment Hazard: Landslide and Flooding Overlay Map OM5.3”.

No. 528 Black Mountain Road, Cooroy

 

Mary River Catchment
Natural Hazard: Landslide &

 

Flooding Overlay
= —™ | Locality -—-<.
(Map OM5.3) 1. . Boundaries Rams eine Boundary
: ailway Line
Property Major Road Network
Boundaries
Landslide Streams, Rivers and
Hazard Area e Drainage Lines
Extent of ii Inset

Flood Mapping Area Subject to

Min Floor Height

 

Flood Hazard Area

 

 

Office al: 1/8 Denna St, Maroochydore, Q, 4558.
Phone: 5443 6622, Fax: 5479 1899, Email: [email protected]

Page 15

SITE PHOTOGRAPHS

 

Job Number: 15960

Page 16

APPENDIX A

SUB-SOTL PROFILES

Report No. 15960

Page 17

Field Investigation Report cont'd
Client: BROAD, PHIL Job No: 15960
Site Location: Lot5, No. 528 Black Mountain Road, Cooroy Your Ref:

 

DCP Values Bofé'No.: 4
per 100mm { of . .
Location: 17m Access Drive Frontage, 30m Bend in Access Frontage Boundary

 

 

 

01 2 42.1 f
1 ge
02 4/22 Depth \ Description Symbol Comments
03 2 /23 / | 250 Silty CLAY low-medium plasticity, grey yellow brown, with fine cL
04 4 |24 sand, trace fine gravel, moist, firm.
05 3 1/25 600 Silty CLAY medium-high plasticity, grey yellow/orange/orange CH
06 3 126 yellow, with fine sand, trace fine-medium gravel, moist, stiff.
0.7 2/27 1200 Gravely CLAY low-medium Plasticity, grey yellow/tight brown, fine- CL
08 28 Coarse gravel, with fine-coarse sand, moist, stifffvery stiff.
182 12,
09 3 |29 3000 / Gravely CLAY low plasticity, light brown, fine-medium gravel, with CLAXW END
. . fine-coarse sand, some silt, interbedded with (XW) rock, moist,
1.0 5 |3.0 very stiff.
1.1 6 13.1
1.2 1143.2
1.3 16 13.3
1.4 3.4
1.5 3.5
1.6 3.6
17 3.7
1.8 3.8
1.9 3.9
2.0 4.0

 

 

 

 

Thursday, 19 May 2011 Page 2 of 5

Page 18

Field Investigation Report cont'd
Client: BROAD, PHIL Job No: 15960
Site Location: Lot 5, No. 528 Black Mountain Road, Cooroy Your Ref:

 

 

NOTES ON REPORT DOCUMENT

(i) The report was prepared for a specific purpose and as directed by the client.

(ii) It should be acknowledged that soil investigations identify actual sub-surface conditions only at
those points where and when samples are taken. Data derived through sampling and/or
subsequent testing are extrapolated to render an opinion about overall sub-surface conditions.
Even under optimal circumstances, actual conditions may differ from those inferred to exist,
because no consultant, no matter how qualified, and no sub-surface exploration programme, no
matter how comprehensive can reveal what is hidden by earth, rock and time. The actual
interface between materials may be far more gradual or abrupt than our report indicates. Actual
conditions in areas not sampled may differ from our predictions. ,

(iii) Interpretation of soil/rock strength terms should refer to our "Glossary of Terms".

(iv) The soil depth referenced in our borelog information profile, represents the “end” depth of each
soil type.

 

 

 

Thursday, 19 May 2011 Page 3 of 5

Page 19

Field Investigation Report cont'd

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Client: BROAD, PHIL Job No: 15960
Site Location: Lot5, No. 528 Black Mountain Road, Cooroy Your Ref:
GLOSSARY OF TERMS
CONSISTENCY OF COHESIVE SOILS
Unconfined Pp
Description Compressive Strength eel
(kPa) N" value
SOFT 0-35 0-4
FIRM 35 - 90 4-8
STIFF 90 - 225 8-15
VERY STIFF 225 - 500 16 - 30
HARD 500 - 700 30 - 50
WEAK ROCK > 900 > 50
CONSISTENCY OF NON-COHESIVE/ GRANULAR SOILS
iti Dry Density SPT
Description (tim3) “N" value
VERY LOOSE < 1.450 0-4
LOOSE 1.450 - 1.600 4-10
MEDIUM DENSE 1.600 - 1.750 10 - 30
DENSE 1.750 - 1.950 30 - 50
VERY DENSE > 1.950 > 50
CONSISTENCY OF CEMENTED SOILS
Unconfined
Description Compressive Strength
(kPa)
WEAKLY 300 - 1500
MODERATELY 1500 - 3500
STRONGLY > 3500

 

 

 

 

Thursday, 19 May 2011

Page 4 of 5

Page 20

Field Investigation Report cont'd

 

 

 

 

 

 

Client: BROAD, PHIL Job No: 15960
Site Location: Lot 5, No. 528 Black Mountain Road, Cooroy Your Ref:
GLOSSARY OF TERMS
ROCK MATERIAL WEATHERING CLASSIFICATION
Term Symbol Definition
Residual! Soil RS Soil developed on extremely weathered rock; the mass

structure and substance fabric are no longer evident;
there is a large change in volume but the soil has not
been significantly transported.

 

Extremely weathered rock XW Rock is weathered to such an extent that it has ‘soil’
properties, i.e. it either disintegrates or can be
remoulded, in water.

 

Distinctly weathered rock DW Rock strength usually changed by weathering. The rock
may be highly discoloured, usually be ironstaining.
Porosity may be increased by leaching, or may be
decreased due to deposition of weathering products in
pores.

 

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

 

STRENGTH OF ROCK MATERIAL

 

 

Term Symbol Point load
index (MPa)
1,50

Field guide to strength

 

Very Low VL >0.03 <0.1 Material crumbles under firm blows with sharp end of
pick; can be peeled with knife; too hard to cut a
triaxial sample by hand. Pieces up to 3cm thick can
be broken by finger pressure.

 

Low L 20.1 <0.3 Easily scored with a knife; indentations imm to 3mm
show in the specimen with firm blows of the pick point;
has dull sound under hammer, A piece of core
150mm long 50mm diameter may be broken by hand.
Sharp edges of core may be friable and break during
handling.

 

Medium M 70.3 <1.0 Readily scored with a knife; a piece of core 150mm
long by 50mm diameter can be broken by hand with
difficulty.

 

High H >4 <3 A piece of core 150mm long by 50mm diameter
cannot be broken by hand but can be broken by a pick
with a single firm blow; rock rings under hammer.

 

 

 

 

 

 

 

 

 

Thursday, 19 May 2011 Page 5 of 5

Page 21

APPENDIX B

EXTRACTS FROM “LANDSLIDE RISK MANAGEMENT CONCEPTS &
GUIDELINES”, FROM THE AUSTRALIAN GEOMECHANICS SOCIETY
SUB-COMMITTEE ON LANDSLIDE RISK MANAGEMENT

1. “SOME GUIDELINES FOR HILLSIDE CONSTRUCTION”

2. “EXAMPLES OF GOOD HILLSIDE PRACTICE”

Report No. 15960

Page 22

LANDSLIDE RISK MANAGEMENT

ADVICE.
GEOTECHNICAL
ASSESSMENT
PLANNING

SITE PLANNING [

APPENDIX J

AGS SUB-COMMITTEE

SOME GUIDELINES FOR HILLSIDE CONSTRUCTION

GOOD ENGINEERING PRACTICE

Obtain advice from a qualified, experienced geotechnical consultant at early
stage of planning and before site works.

Having obtained geotechnical advice, plan the development with the risk
arising from the identified hazards and consequences in mind.

DESIGN AND CONSTRUCTION

POOR ENGINEERING PRACTICE

Prepare detailed plan and start site works before
geotechnical advice.

Plan development without regard for the Risk]

 

HOUSE DESIGN

Use flexible structures which incorporate properly designed brickwork, timber
or stecl frames, timber or patel cladding.

Consider use of split levels,

Use decks for recreational areas where appropriate,

Floor plans which require extensive cutting and
filling,
Movement intolerant structures,

 

SITE CLEARING

Retain natural vegetation wherever practicable,

Indiscriminately clear the site.

 

ACCESS &
DRIVEWAYS

Satisfy requirements below for cuts, fills, retaining walls and drainage.
Council specifications for grades may need to be modified.
Driveways and parking areas may need to be fully supported on piers,

Excavate and fill for site access before
geotechnical advice,

 

EARTHWORKS

Retain natural contours wherever possible.

Indiscriminant bulk earthworks.

 

curs

Minimise depth.
Support with engincered retaining walls or batter to appropriate slope,
Provide drainage measures and erosion control.

Large scale euts and benching,
Unsupported cuts,
Ignore drainage requirements

 

Fis

Minimiss height,

Strip vegetation and topsoil and key into natural slopes prior to Alling.
Use clean £1] materials and compuct to engineering standards.

Batter to appropriate slope or support with engineered retaining wall,
Provide sucface drainage aud appropriate subsurface drainage.

Loose or poorly compacted fill, which if it fails,
may flow a considerable distance including
onto property below,

Block natural drainage lines,

Fill over existing vegetation and topsoil,
Include stumps, trees, vegetation, topsoil,
boulders, building rubble etc in fill.

 

ROCK OUTCROPS
& BOULDERS
RETAINING
WALLS

Remove or stabilise boulders which may have unacceptable risk.
Support rock faces where necessary.

Disturb or undercut detached blocks or
boulders,

 

Engineer design to resist applicd soil and water forces.
Tound on rock where practicable,

Provide subsurface drainage within wall backfill and surface drainage on slope
above.

Construct wall as soon as possible after cut/fill operation.

 

FOOTINGS

Construct @ structurally inadequate wall such as
sandstone flagging, brick or unreinforced
blockwork,

Lack of subsurface drains and weepholes.

 

Found within rock where practicable,
Use rows of piers or strip footings oriented up and down slope.
Design for lateral creep pressures ifnecessary,

Backfill footing excavations to oxclude ingress of surface water.

 

SWIMMING POOLS

Found on topsoil, loose fill, detached boulders.
or undercut cliffs.

 

Engineer designed.

Support on piers ta rock where practicable,
Provide with under-drainage and gravity drain outlet where practicable,
Design for high soil pressures which may develop on uphill side whilst there

 

 

DRAINAGE.
SURFACE

may be little or no lateral support on downhill side.

Provide at tops of cut and fill slopes.

Discharge to street drainage or natural water courses,

Provide general falls to prevent blockage by siltation and incorporate silt traps.
Line to minimise infiltration and make flexible where possible.

Special structurcs to dissipate cnerpy at changes of slope and/or direction.

Discharge at top of fills and cuts.
Allow water to pond on bench areas,

 

SUBSURFACE

Provide filter around subsurface drain.

Provide drain behind retaining walls.

Use flexible pipelines with access for maintenance,
Prevent inflow of suzface water.

Discharge roof runoff into absorption trenches,

 

Seetic &
SULLAGE

Usvaily requires pump-out or mains sewer systems, absorption trenches may
be possible in some areas if risk is acceptable.
Storage tanks should be water-tight and adequately founded.

 

Discharge suillage directly ovto and into slopes.
Use absorption trenches without consideration
of landslide risk,

 

EROSION
CONTROL &
LANDSCAPING

Control erosion as this may lead to instability.
Revegetate cleared area.

Failure to observe earthworks and dramage
recommendations when fandscaping.

 

DRAWINGS AND SITE VISITS DURING CONSTRUCTION

 

DRAWINGS

Building Application: drawings should be -yiewed by geotechnical consultant _|

 

SITE VISITS.

 

INSPECTION AND MAINTENANCE BY:OWNER

Site Visits by consultant may be appropriate during construction/

 

OWNER'S
RESPONSIBILITY

 

 

Clean drainage systems; repair broken joints in drains and leaks in supply
pipes.

Where structural distress is evident see advice,

[f seopage observed. determine causcs ar seck advice on consequences,

 

 

 

Australian Geomechanics — March 2900 91

Page 23

LANDSLIDE RISK MANAGEMENT AGS SUB-COMMITTEE

 

EXAMPLES OF GOOD HILLSIDE PRACTICE

  
   
 
 
   

PUXGLE
srauctone \

ROOF WATER
APCD OFF StIE
gern

 

SS waante oF sot
Te Race Feces
ACOLLU VLR

 

 

 

 

(np CICS

mito Roc

 

   

OFF STREET
Pt

    
 
 

SUBSOR DRAWAGT HAT

yo BE REQURED INSLOPE
SEWERAGE EFFLUENT PUMPED-OUT .

OR CONNECTED TO SEWER.
TANKS ADEQUATELY FOUNDED.
ENGUETRED RF IMRINSG WALLS

ATH SURFACE & SUBSURFATE
DRASIAGE CONS TRUCTEO
BEFORE HOUSE

 

EXAMPLES OF POOR HILLSIDE PRACTICE

LAISTABLISED AOCK ToPeLES
VEGETATION. AND TRAYLLS GOWHSLOPE
REMOVED :

  
 
 

   
     
  
 
 
  

STRUCTURE UNABLE
10 TOLERATE

“Y dISCHARGES DFS
TT RMENT ROSFWATER
SUTTLEHEUT & CRACKS Soap aay \

  
 

POORLY CONPACTEA Fitim.,
SETTLES UREVENLY
‘AND PACKS POOL

 

LOOSE, SATURATED FLL SLIGES
AMD POSSHLY FLOWS ODIANSLOPC

 
 
 
 
 
 
  
     
 
  

“ROOPYATTR NTROGUCEO

syapcourateny \ ‘NTO StaeC
ant
or \ . LOUISE HOT FOLIRED
VEGETA Tt ‘OY BrDROLK
REMOVED Ye

SLOPE Falls

 

 

POHOSD WATER ENTERS

BN SLOPE & ACTIVATES SUP
* \C possaur reavee povnisrore wien

RACES ORR SEVELORENT

  

 

 

Figure J1 Tlustrations of Good and Poor Hillside Practice

92 Australian Geomechanics — March 2000