RFI - Attachment C - Slope Stability Assessment and Geotechnical report · MCU20/0026

Project No. 1-22543                                                                                                          Page | 9
June, 2020
Ref: 1-22543, 2020-05-20, BR SSA VER 1
Sanya Holdings – Slope Stability Assessment and Geotechnical Report - Proposed Residence, 40 Park Crescent, Sunshine Beach




           4.3.3       Hazard A - Natural Shallow Landslide

The site was assessed using the parameters as described by MacGregor and Taylor (2001)
and the site features identified on the supplied information, observations made whilst on site
and where necessary worst case parameters.

Therefore, based on this assessment, natural shallow landslides on the site have been given
a likelihood hazard rating of Low. This rating translates to a Likelihood Descriptor of Rare to
Unlikely.

           4.3.4       Hazard B - Proposed Cuts

Cuts are understood to be proposed within the site for the basement level floor. Given the
adjacent structures, this level is expected to be within approx. 1.0 to 1.5m from the southern
boundary.

Based upon previous similar types of structures in the area, we expect that all cuts will be
supported temporarily during construction by sheet pile walls then permanently by construction
of other retaining structures. To assess these cuts, the method outlined by MacGregor & Taylor
(2001) for the assessment of cuts has been adopted. No batters are expected to be adopted
for excavations.

The assessment has taken into account the proposed wall geometry (based on provided
drawings and site measurements), expected subsurface profile (from site investigation) and
proposed development (based on provided drawings).

Information in relation to the design parameters or structural elements of the wall is not
available at this stage. Therefore, the assessment has also assumed that all retaining walls
(both temporary and permanent) will be adequately engineer (RPEQ) designed and certified.

Assuming all cuts are adequately supported by retaining structures and that no evidence of
instability is noted in the cuts once completed, then a likelihood hazard rating of Low to
Moderate would apply to the temporary cuts. This translates to a Likelihood Descriptor of
Unlikely.

However, once suitable permanent retaining structures are in place, the hazard rating would
drop to Low which translates to a Likelihood Descriptor of Rare to Unlikely.

Note: The above assumes that all retaining structures on the site are designed by a
suitably qualified RPEQ and constructed in accordance with their design.

           4.3.5       Hazard C - Scour of Exposed Surfaces

As noted above, the methods as adopted for Hazards A and B do not have a corresponding
method for the analysis of scour (Hazard C). The following comments will allow the hazard to be
assessed:-

          The proposed development is likely to require the clearing and exposure of soil over
           essentially the entire site (slope angles generally of 5º to 25º).
          The exposed surfaces would most likely be fill and sandy soils.
          Experience with these types of materials would suggest that the exposed material would
           scour easily if left exposed and water is allowed to run over the slopes.


                                                                                                               SOIL SURVEYS