Geotechnical Stability Report · OPW24/0017

GMW Projects Pty Ltd                                                                             24008-001-Rev0
                                                                                                 31 January 2024

It is therefore recommended that site specific static load testing be conducted from screw piles, if adopted, at
a minimum. Where tension or compression capacity developed in the footings is critical for the future
structure (e.g. resistance to uplift forces from high winds), then cyclic load tests (including measurement of
deflections under tension and compression cycles) should also be undertaken prior to construction.
Kentledge for static testing, or simulated cyclic loads, should prove the piles to a minimum of two times the
expected working load within tolerable deflections.

All footings should found such that they are not adversely affected by (or affect) any adjacent excavations,
trenches or retaining walls that are not designed to support building loads. Footings should found at least
below a plane extending 1 m horizontally from the base of trenches/excavations/retaining walls, then rising
up at 1V:1H, as illustrated in Text Figure 8.

Where footings are located within a horizontal distance of 1.5H (H being the batter height) of any cut or fill
batter crest, these footings must be founded at a depth level with the toe of the batter.




Text Figure 8: Footing depth required to prevent undermining

Site drainage should be designed to readily remove surface water and to prevent ponding of water on
subgrade areas during construction and also adjacent to foundations and perimeter slabs once construction
is completed.

If bored piles are adopted, it is recommended that footings be inspected by an RPEQ prior to placement of
steel reinforcement and pouring of concrete to confirm allowable bearing pressures and cleanliness of
excavations.

If any soil conditions encountered during construction are found to differ from those noted in the geotechnical
investigation, Tectonic and Global should be notified immediately, and an inspection carried out to determine
if changes to footing design are required.

4.4    Retaining Walls
Retaining structures must be founded as per the recommendations in Section 4.3 above. 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.
The parameters outlined in Table 3 overleaf may be adopted for retaining wall design. The values in Table 3
assume that the walls are fully drained, and no allowance is included for hydrostatic pressures, construction
loading, up-slope footing loadings, the effects of sloping ground and backfill compaction stresses. Any
temporary shoring required to support excavations during construction may also be designed using the
parameters in Table 3.




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