Avocet Pde OPW - App E Slope · OPW20/0092

AUSTRALIAN GEOGUIDE LR6 (RETAINING WALLS)

Old Masonry walls (Figure 4) - Many old masonry retaming walls have
not been built in accordance with modern design standards and often
have a low “factor of safety” (GeoGuide LR1). They may therefore be =~=—__ thickrees

close to failure and a minor change in thew condition, or loading, could =>,

initiate collapse. You need to take particular care with such structures \

and seek professional advice sooner rather than later. Although masonry

walls sometimes deflect significantly over long periods of time collapse. ie
when it occurs, is usually sudden and can be catastrophic. Familiarity
with a particular situation can instil a false sense of confidence.

Reinforced soil walls (Figure 5) - are made of compacted select fill in Sere

which layers of reinforcement are buried to form a “reinforced soil zone”. _
The reinforcement is all important, because it holds the soil “wail” "7 7
together. Reinforcement may be steel strip, or mesh, or a variety of SS 22

geosynthetic (‘plastic’) products. The facing panels are there to protect
the soil “wall” from erosion and give it a finished appearance.

Most reinforced soil walls are proprietary products. Construction should
be carried out strictly in accordance with the manufacturer's instructions.
inspection and maintenance should be the same as for formed concrete
and concrete block walls. If unusual materials such as timber, or used
tyres, are used as a facing it should be checked to see that @ is not rotting,
or penshing.

OTHER WALLS

Cantilevered and anchored walls (Figure 6) - rely on earth pressure on
the low side, rather than self-weight, to provided the restoring force and
an adequate factor of safety. These walls may comprise:

« a line of touching bored piers (contiguous bored pile wall) or

* sprayed concrete panels between bored piers (shotcrete wall) or

*  honzontal timber or concrete planks spanning between upright timber Figure 5 - Typical reinforced soil wall
or steel soldier piles or

« steel sheet piles.

Depending on the form of construction and ground conditions, walls in

excess of 3 m height normally require at least one row of permanent

 

= Ground anchor
—— (nee requared ter

ground anchors. J caminvered wal)
INSPECTION me

- . 4
Al walls should be inspected at least once a year, looking for tiltmg and >_< Retwinirg wall

other signs of deterioration. Concrete walls should be inspected for Ca

cracking and rust stains as for formed concrete gravity walls. Contiguous

bored pie walls can have gaps between the piles - look for loss of soil

from behind which can become a major difficulty if it is not corrected. :
Timber walls should be inspected for rot. as for timber crib walls. Steel

sheet piles should be inspected for signs of rusting. In addition, you = =
should make sure that ground anchors are maintained as described in = 7 .
GeoGuide LR4 under the heading "Rock bolts and rock anchors”. Pee. eres

One of the most important issues for walls is that their internal draimage systems are operational. Frequenty verity that
intemal drainage pipes and surface interception drains around the wall are not blocked nor have become inoperative.

More information relevant to your particutar situation may be found In other Australian GeoGuldes:

GeoGuide LR7 - Landslide Risk

GeoGuide LRA = - Hillside Construction
GeoGuide LR3 - Effluent & Surface Water Disposal
GeoGuide LR4 -Landsides In Rock GeoGuide LR10 - Coastal Landsiides

GeoGuide LRS - Water & Drainage GeoGuide LR11 - Record Keeping

The Austafan GeoGuides (LR series) are a set of publications Intended for property owners; local councis; planning authontes:
Gevelopers; Insurers; lawyers and, In fact, anyone who lives with, or has an interest in, a natural or engineered slope, a cutting, or an
excavaton. They are intended to help you understand why slopes and retaining stuctures can be a nazard and what can be done with
appropiate professiona! advice and local council approval (if required) to remove, reduce, or minimise the risk they represent. The
GeoGuides Nave been prepared by tne Austaian Geomechanics Society a specialist technical society within Engineers Austrata, the
natonal peak body for al engineering disciplines in Australia, whose members are professiona@ geotechnical engineers and engineering
geologists with 2 particular Interest in ground engineering. The GeoGuldes have been funded under the Australian govemments' National
Olsaster MMigation Program

GeoGuide LR1 - Introduction
GeoGuide LR2 -Landsides
GeoGuide LR3 - Landsides In Soll

 

Australian Geomechanics Vol 42 No 1 March 2007 73