Geotech Report · OPW26/0094

Project No. PG-10899                                                                                                 Page | 6
November 2023
Ref: PG-10899, 2023-10-16, GR VER 1
DD Sunnyside CD Sunnyside Pty Ltd – Geotechnical Investigation - Proposed Residence, 30 Mossman Court, Noosa Heads




     •     Field density testing should be carried out to check the standard of
           compaction achieved and the placement moisture content. The frequency
           and extent of testing should be as per guidelines in AS.3798-2007.

8.0 BATTERS – SHORT TERM EXCAVATION PROFILE

It is understood that cut batters to 3m in height will be required as part of the
basement construction.

Considering the proposed maximum height of cut, the following recommendations
are made for the bulk excavation of the site.

Batters < 2.0m in height

     •     1V:1.5H batter with crest of batter >2m from buildings or structures.
Batters > 2.0m in height

     •     1V:1.5H batter with the crest of the batter at least 2.0m inside the site
           boundary.
     •     2.0m minimum distance from any building or structure.
If batters are to be left exposed for an extended period of time, a battler angle of
1V:2H is recommended and berm widths are to be strictly maintained. The above
batter slopes assume no seepage is present in the batters and the batters are above
the water table.

9.0 TEMPORARY BATTER SUPPORT

Where the excavations cannot be battered to a stable angle, they will need to be
supported to prevent instability. Support systems could include:

     •     Sheet Piles – anchoring or cross-bracing of the excavation are likely to be
           required for sheet piles or possibly cantilevered, and due consideration should
           be given to the potential for anchor installation and vibration to adversely
           affect adjacent areas.
     •     Contiguous Piles – whilst no vibration is associated with their installation, it is
           likely a more expensive solution.
     •     Steel Soldier Piles and Jetted Precast Panels – difficulties in maintaining
           stability whilst jetting the panels and is likely to be a higher risk option.
Where sheet piles are to installed through medium dense or ‘denser’ sands, pre-
drilling may be required to ensure installation.

Where sands are retained, shoring pressures should be based on the lateral earth
pressure coefficients given in Table 2, in conjunction with a triangular pressure
distribution where the pressure can be calculated from P=0.5ka  H2, provided the
excavation is not surcharged by adjacent buildings/services and some tolerance or
movement exists.