Avocet Pde OPW - App E Slope · OPW20/0092

AUSTRALIAN GEOGUIDE LR8 (CONSTRUCTION PRACTICE)
EXAMPLES OF POOR HILLSIDE CONSTRUCTION PRACTICE

Unstabllised rock topples and Iravets downsiope
Vegelation removed
Steep unsupported out fils

Discharges of rootwater soak away ralher than
conducted offsite of to secure storage for re-use

Structure unable te tolerate ae
ecitement and cracks oo ™~
Poory compacted 4 setties «’ * A
unevenly and cracks pool tf

inadequate walling unable i
fo support fH Ir

inadequately

 
 
  
  
 
   
 
  
  
 
   

Lose. sabaatad fill slides avd

possitty News downslope
Ponded water enters stope and actvates landskde 1 vie yay
= ~Prestte travel ccrensiope which impacts other development dawnt! San wea ASE OPO Ascordm |

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 quantites and level the site leaving unstable cut faces and added
large surface loads to the ground. Fadure to compact the fill properly has led to settlement, which will probably continue
for several years after completion. The house and poo! 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 fated.
creating a very 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 inte the ground and raises the water table (GeoGuide LR'5}. 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.
pattem. This may conflict with the requirements for effuent and surface water disposal (GeoGuide LRQ) 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 3 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 GeoGuldes:

« GeoGuide LR1 - introduction « GeoGuide LR6 - Retaining Wals

* GecoGuide LR2 -Landsides « GeoGuide LR7 - Landslide Risk

« GeoGuide LR3 -Landsides In Soll « GeoGuile LRS -EfMivent & Surface Water Disposal
* GeoGuide LR4 -Landsides In Rock GeoGuite LR10 - Coastal Landslides

«  _GeoGuide LAS -Water & Drainage « GeoGuide LR11 - Record Keeping

 

The Australian GeoGuides (LR series) ae a set of publications Intended for property owners; local councils; planning autnodtes;
Gevelopers; insurers: (awyers and, in fact, anyone who lives with, or has an interest in, a natural of engineered stope, 3 cutting or an
excavaton. They ae intended to help you understand why slopes and retaining structures can be 3 Nazard and what can be done wtn
appropriate advice and local counc! approval (if required) to remove, reduce, of minimise ine risk they represent The
GeoGukles have been prepared oy the Ausirailan Geomechanics Society, a specialist technica society wifin Engineers Australia, the
ational peak body for ail engineering disciplines in Australia, wnose members are professiona geotechnica’ engineers and engineering
geologists with 3 particular interest n ground engineering. Tne GeoGuites nave Deen funded under tne Australian governments’
Nationa Disaster Misgation Program.

Australian Geomechanics Vol 42 No 1 March 2007 75