Geotech

                              PROPOSED UNIT DEVELOPMENT
                              27 BOTTLEBRUSH AVENUE, NOOSA HEADS

sands at the subgrade level high-level footings may be adopted. It should be noted that excavations for
concrete strip footings (or similar) may loosen the base. Therefore, the use of a vibrating plate would be
required to densify any high-level footing bases prior to the placement of reinforcing steel.
Due to the presence of loose sands and nearby structures, open bored piers or driven piles are not
recommended for this site and it is expected that steel screw piles could be utilised. Steel reinforced
concrete bore piles may be possible; however, the use of sacrificial liners (e.g. Formatube) would be
required. The advice of a specialist piling contractor must be sought regarding feasibility, design and
installation of the piling system for this site, including an assessment of potential vibration effects on nearby
structures, and monitoring requirements.

If steel screw piles are adopted, it will be important to ensure close supervision of installation, as piling may
not encounter sufficient drilling resistance (from torque measurement) in sands at the suggested founding
depth, and piles could extend to much greater depth than necessary.

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




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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.
Footing design should also account for potential soil reactivity to be equivalent to Class M. It should be noted
                            AF
that placement of reactive clay may result in a more severe equivalent site classification, such as H1 or
greater.

All footings should found such that they are not adversely affected by any adjacent excavations, trenches,
retaining walls, or in ground structures 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/swimming pool, then rising up at 1V:1H, as illustrated in Text Figure 10.
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                        Text Figure 10: 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.

It is recommended that footings be inspected by a suitably qualified and experienced engineer prior to
placement of steel reinforcement and pouring of concrete to confirm allowable bearing pressures and
cleanliness of excavations.




10 November 2021
Report No. 21286-001-Rev0                               12