35484 Approved Plans Ba · MCU21/0222.01

LANDSLIP MECHANISMS

Landslip is generally defined as the movement of a mass of rock or soil down a slope.

It is generally considered to occur when the strength of the soil or rock mass to support itself is exceeded causing
movement to occur within the mass.

This loss of strength can occur as a result of numerous circumstances. These include, but are not limited to the
following:-

- Siesmic Activity

- Erosions effects such as wind or fluid scour

- Soil Saturation from rainfall events or defective drainage measures

- Construction/Earthworks activities

- Groundwater variations/movements

- Previous Landslips

The nature of landslips vary with site specific conditions and failure mechanisms that cause the slips to occur.
Appendix B provides some diagrammatic examples of various landslips.

The speed of landslips can vary greatly from millimetres per year to a number of meters in a matter of minutes.
Once again this characteristic is governed by site specific conditions and the failure mechanism causing the slip
to occur.

The allotment is situated within a massive aeolian sand bed of Quaternary age. As a general observation dunal
horizons such as these are stable where;

- The natural slope is less than the angle of repose for sand (30°)

- Vegetation exists to protect from wind generated scour

- The drainage pattern is such that there is no risk of fluvial scour.
These horizons can become unstable when aeolian or fluvial scour erode slopes to angles greater than 30°,
particularly when coincident with vegetation removal.
LANDSLIP HAZARD ASSESSMENT
For our assessment we utilize the Guidelines For Landslip Risk Management Framework as provided by the
Australian Geomechanics Society, in their journal of March 2007. Descriptions used by this framework can be

found appended to this report.

Using the Qualitive Risk Analysis Matrix (refer appendix) we have established the following characteristics for the
allotment.

Landslip Mechanism § Translational or Rotational Flow or Creep Movement
We consider a potential landslip mechanism will consist of either a Rotational or Translational Landslide or Creep
movement within the sloping profile. Diagramation representation of these mechanisms are appended to this
report. We are of the opinion that this movement could occur within the Loose Sand profiles.

Likelihood of Landslip : Possible
This is due to the proposed earthworks for the proposed construction.

Consequences to Property : Medium
With these factors considered we classify the allotment as:-

MODERATE RISK OF LANDSLIP

Although we consider the allotment has a moderate risk of landslip, building work undertaken on the site should
follow accepted methods which assist in maintaining slope stability.

Such measures are discussed in the following section.

SCG Consulting Engineers 3 SCG Ref: 32027(SL)