Information response - GEOTECH REPORT

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