Reference Document - MCU24/0023

GJ Gardner Homes Gympie                                                                                 23236-001-Rev0
C/- Covey Associates Pty Ltd                                                                              7 August 2023




Text Figure 13: Zone of influence diagrams – footings to be founded below these lines

Footing bases must be cleaned following mechanical excavation to expose undisturbed materials over the
full base area. Should bored piles be required, it is essential that the piling contractor have a ‘mud bucket’
or similar to enable clean out of the pile bases.

A structural/geotechnical RPEQ should inspect the footing excavations to confirm appropriate foundation
materials and cleanliness prior to pouring concrete. If any soil conditions encountered during construction
are found to differ from those noted above, Tectonic and Ground Drill must be notified immediately, and an
inspection carried out to determine if changes to footing design are required.

4.4     Retaining Walls
Retaining structures greater than 1 m high, or those required to support surcharge loads or sloping backfill,
will require engineer design and certification of construction. Retaining wall design should be carried out in
accordance with AS4678-2002 Earth retaining structures.

Design for retaining structures could be carried out using a pressure distribution applicable to the wall type
and based on the parameters listed in Table 3. These values do not include allowance for hydrostatic
pressures nor transient (e.g. construction) or adjacent footing loadings.

Table 3: Retaining Structure Design Parameters

                                                                          Lateral earth pressure coefficients
                                  Unit
                                             Friction
 Retained material              weight
                                             angle (°)             Ka                        Ko
                                (kN/m3)                                                                         Kp
                                                            (Cantilever wall)        (Non-yielding wall)


 Stiff (or stiffer) Clays          18            27                  0.38                    0.55               2.66



 Future Fill*                       *             *                   *                       *                  *

Note:     * Depends on fill material type and level of compaction.

As a minimum, retaining structures must be founded as per the recommendations in Section 4.3 above with
the footings also designed to account for lateral loads imposed by the retaining wall. Detailed design must
include an assessment of internal and global stability, together with required bearing capacity and founding
depth, by the retaining wall design engineer.




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