Avocet Pde OPW - App E Slope · OPW20/0092

AUSTRALIAN GEOGUIDE LR2 (LANDSLIDES)

Rotational or circular slip failures (Figure 1) - can occur on Small scale
moderate to very steep soil and weathered rock slopes (Table fandsiide:
1). The sliding surface of the mowing mass tends to be deep
seated. Tension cracks may open at the top of the slope and
bulging may occur at the toe. The ground may move in
discrete "steps" separated by long periods without movement.
More rapid movement may occur after heavy rain.

Translational slip failures (Figure 2) - tenc to occur on
moderate to very steep slopes (Table 1) where sod, or weak
rock, overlies stronger strata. The sliding mass is often
relatively shallow. It can move, or deform slowly (creep) over
long periods of time. Extensive linear cracks and hummocks
sometimes form along the contours. The siding mass may
accelerate after heavy rain.

Wedge failures (Figure 3) - normally only occur on extreme
slopes. or cliffs (Table 1). where discontinuities in the rock are
inclined steeply downwards out of the face.

Rock falls (Figure 3) - tend to occur from cliffs and
overhangs (Table 1).

Clifis may remain apparently unchanged for hundreds of
years. Collections of boulders at the foot of a cliff may
indicate that rock falls are ongoing. Wedge fadures and rock
falls do not “creep”. Familiarity with a particular local situation
can instil a false sense of security since failure, when @
occurs, is usually sudden and catastrophic.

 

Debris flows and mud slides (Figure 4} - may occur in the
foothills of ranges. where erosion has formed valleys which
slope down to the plains below. The valley bottoms are often
lined with loose eroded material (debris) which can “flow” if it
becomes saturated during and after heavy rain. Debris fows
are likely to occur with little warning: they travel a long way
and often involve large volumes of soll. The consequences
can be devastating.

 

Figure 4
More information relevant to your particular sttuation may be found In other Austrailan GeoGuldes:

GeoGuide LR1 - Introduction
GeoGuide LR3  - Soll Slopes
GeoGuide LR4 - Rock Slopes

GeoGuie LR? - Landslide Risk

GeoGuile LRS - Hillside Construction

GeoGuiie LAS - EfMfivent & Surface Water Disposal
GeoGuide LRS - Water & Drainage GeoGuie LR10 - Coastal Landslides

GeoGuide LR6 - Retahing Walls GeoGuile LR11 - Record Keeping

The Australian GeoGuides (LR series) we a set of pubications Intended for propery owners; loca’ councils: planréng authorities;
Gevelopers; Insuress; lawyers and. in fact, anyone who fives with, or has an interest in, a Natura! or engineered slope. a cutting. or an
excavation. They are intended to help you understand why slopes and retaining structures can be a hazaré and what can be done with
appropriate professional advice and local counc!) approval (9 required) to remove, reduce, or minimise the ns& they represemt. The
GeoGuides Nave Deen prepared by the Australian Geomechanics Society, a speciaiist technica society within Engineers Austrata, the
national peak body for ali engineering Gecpiines in Australla, whose members are professiona geotectiinica’ engineers and engineering
gedlogisis with a particular interest in ground engineering. The GeoGuides have been funded under the Australian govemments’
Nationa! Disaster Mitgation Program.

 

Australian Geomechanics Vol 42 No 1 March 2007 163