Att 3 - Landslide Risk Assessment

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                                   UNDERSTANDING THIS REPORT


The soils encountered on this subject site have been identified as expansive/reactive soils which
have a potential to change volume with changes in soil moisture.

These soil moisture variations can be generated naturally (by rain or lack of rain), by nearby
vegetation, either new plantings, existing tree(s) being removed or allowed to continue to grow, or
by poor site drainage, where water is allowed to pond or accumulate near the footing system.
Another significant cause can be broken or damaged service pipes which carry water near or under
the dwelling. These factors are outlined in AS2870-2011, Section 1.1 and are known as: “Abnormal
Moisture Conditions"

In preparing this report, we have used our experience and current scientific knowledge to determine
the various parameters needed by your Engineer to design an economical footing system which will
provide serviceability within the AS2870 performance criteria for the life expectancy of the dwelling.

At the time of our testing we had an understanding of the soil moisture content, and we derived a
‘Design Movement’ value in ‘mm’. We then use to following matrix to arrive at a ‘Risk of’ potential
for this site:

 Potential for Long Term Uplift (Heave)
                           Wet                Moist               Neutral         Slight Dry               Dry
                         MC>>PL              MC>PL               MC=PL             MC<PL                MC<<PL
     < 20mm           Not Creditable        Very Low               Low               Low               Moderate
    21-40mm             Very Low              Low               Moderate          Moderate                High
    41-60mm                Low                Low                  High              High              Very High
    61-75mm                Low              Moderate            Very High         Very High             Extreme
   76-100mm                Low              Moderate             Extreme           Extreme            Very Extreme
    > 100mm                Low              Moderate           Very Extreme      Very Extreme         Very Extreme
 Potential for Long Term Settlement
                           Wet                 Moist              Neutral          Slight Dry              Dry
                         MC>>PL              MC>PL               MC=PL              MC<PL               MC<<PL
     < 20mm             Moderate               Low                 Low             Very Low           Not Creditable
    21-40mm                High             Moderate            Moderate              Low               Very Low
    41-60mm             Very High              High                High               Low                  Low
    61-75mm              Extreme            Very High           Very High          Moderate                Low
   76-100mm            Very Extreme          Extreme             Extreme           Moderate                Low
    > 100mm            Very Extreme        Very Extreme        Very Extreme        Moderate                Low

An estimation of bearing pressures may be interpreted by the design engineer’s review of Pocket
Penetrometer (PP) and Dynamic Cone Penetrometer (DCP) readings. Below is a summary of
minimum readings necessary to obtain the allowable bearing capacities nominated.

 Allowable Bearing Values           <50            50             100            150            250           300+
 (kPa)

 Min DCP Readings                    1             2               4              6              9             12

 Min PP Readings                   < 100          100             200            300            500            600


General Notes
This is a site classification report generally in accordance      request, we can do this. Where the site preparation is
with AS 2870-2011 and should be sufficient for a qualified        stated as “known”, our classification is based on the data
person to design footings for structures covered under the        given, as we envisage the finished building footprint (which
scope of this standard.                                           conforms to the AS 2870-2011 guidelines), therefore re-
Where our proposed earthworks specification states                classification is only required if these guidelines change.
“Unknown”, AS 2870-2011 Clause 2.5.2 requires the site            This report may not be adequate for large complex
to be reclassified prior to footing construction if the           dwellings that are generally outside the scope of AS 2870-
proposed cut exceeds the lesser of 0.25Hs or 500 mm and           2011.
the proposed fill exceeds the limits in Clause 2.5.3 of AS        AS 2870-2011 contains a system of classifying soils based
2870-2011. In these instances, the site classification is in      on their ability to change volume with changes in soil
the “as tested” state and may not reflect the final site          moisture. These classes are Class A, Class S, Class M,
classification after earthworks.         Normally this re-        Class H1, Class H2 and Class E (the most severe). These
classification is done by the design engineer, but upon
AWT 77775 Site Classification Report
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