Avocet Pde OPW - App E Slope · OPW20/0092

AUSTRALIAN GEOGUIDE LR4 (LANDSLIDES IN ROCK)

ROCK SLOPE HAZARD REDUCTION MEASURES

Removal of loose blocks - may be effective but, depending on rock type, ongoing erosion can result in more blocks
becoming unstable within a matter of years. Routine inspection. every 5 or so years, may be required to detect this.

Rock bolts and rock anchors (Figure 5) - can be installed in the
ground to improve its strength and prevent individual blocks from
falling. Rock bolts are usually tightened using a torque wrench, whilst
rock anchors carry higher loads and require jacking. Both can be
designed to be “permanent” using stainless steel, or sheathing. to
inhibit corrosion, but the cost can be up to 10 times that of the
“temporary” alternative. You should inspect rock bolts and rock
anchors for signs of water seepage, rusting and deterioration around
the heads at least once every 5 years. If you notice any of these
warning signs, have them checked by a geotechnical practitioner. It
is recommended that you keep copies of design drawings and
maintenance records (GeoGuide LR11) for the anchors on your site
and pass them on to the new owner should you sell.

Rock fall netting, catch fences and catch pits (Figure 6) - are
designed to catch or control falling rocks and prevent them from
damaging nearby property. You should inspect them at least once
every 5 years, and after major falls, and arrange for fallen and
trapped rocks to be removed if they appear to be filling up. Check for
signs of corrosion and replace steel elements and fixings before they
lose significant strength.

 

Cut-off drains (Figure 7) - can be used to intercept surface water
run-off and reduce flows down the cliff face. Suitable drains are often
excavated into the rock, or constructed from mounds of concrete, or
stabilised soil, depending on conditions. Drains must be laid to a fall
of at least 1% so they drain adequately. Frequent inspection is
needed to ensure they are not blocked and continue to function as
intended.

Clear trees and large bushes (Figure 7) - from slopes since roots
can prize boulders from the face increasing the landslide hazard.

 

Figure 7

Natural cliffs and bluffs - often present the greatest hazard and yet are easily overlooked, because they have “been there forever".
They can exist dove 3 bulding, road. or Déach, presenting the risk of a rock falling onto whatever Is Delow. They aiso sometimes
Support bulidings with a fine view to the Moron. Cil's should be observed frequently to ensure that they are not deteriorating. You may
fing f convenient to use binoculars to jook for signs of exposed “fresh” rock on the face, where a recent fail has occurred, or to go to the
foot of the cit? from time to time to see If debris is collecting. A thorough inspection of 2 cliff face Is often a major task requiring the use
Of rope access methods and should only De undertaken by an appropriately q mera meagan if tension cracks are observed In the
ground ane top 3. tate melas acto, ence Mey cous aa miner fare If you have any concems at ail about the

 

More information relevant to your particular stuation may pe found in other Australian GeoGuiies:

GeoGuide LR1  - introduction GeoGuide LR? - Landslide Risk

GeoGuide LR2 -Landsides GeoGuide LRS - Hillside Construction

GeoGulde LR3 - Landslides In Soll GeoGuide LRS - EMuent 4 Surface Water Disposal

GeoGuide LRS  - Water & Drainage GeoGuide LR10 - Coastal Landsiides

« GeoGuide LR6 -Retamingwais GeoGuide LR11 - Record Keeping

The Austratan GeoGuides (LR series) are a set of pubéications intenoed for property owners; local councils; planning authorties;

developers; Insurers; lawyers and, In fact, anyone who Eves with, or has an Interest in, a natural or engmesred slope. a cufing, or an

excavation. They are intended to help you understand why slopes and retaining structures can be 2 nazard and what can be done with

appropriate professional advice and local council approval (If required) to remove, reduce, or minimise the ns& they represent. The

GeoGuides Nave Deen prepared by the Australian Geomechanics Society, 2 specialist technica society within Engineers Austrata, the

nabonal peak body for af engineering disciplines in Australia, whose members are professional gectechnical engineers and engineering
ts wih a particutar interest in ground engineering. The GeoGuides have deen tunded under the Australian govemments’

Nationa’ Disaster Miigation Program.

Australian Geomechanics Vol 42 No 1 March 2007 167