Meyer Judgment Sealed

 

tecténic PROPOSED RESIDENTIAL DEVELOPMENT
geotechnical & environmental a 39 PICTURE POINT CRESCENT, NOOSA HEADS

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.

J TRENCH BACHFILL

 

 

 

 

 

 

 

 

 

 

Text Figure 10: Footing depth recommended to minimise risk of 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 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 should be notified immediately and an inspection carried out to determine if changes
to footing design are required.

6.4 Temporary and Permanent Retention

Excavations are expected to range up to around 3 m to 4 m BGL (existing ground levels) and, given that the
planned excavation extends close to some of the site boundaries and underground infrastructure (e.g.
sewer), some form of temporary shoring will likely be required to support the excavation(s).

Based upon our experience with similar sites, we anticipate that temporary shoring may be achieved by use
of sheet piles, however Unitywater requirements for the sewer may restrict the use of sheet piles. Shoring of
deeper cuts would likely require lateral restraint, and this is conventionally achieved by helical steel anchors
(similar to screw piles). However, the proximity to neighbouring properties would require permissions to be
obtained for subterranean access. Therefore, where lateral support by cantilever only is not feasible, it is
suggested that internal struts/propping be considered to provide lateral restraint for the shoring system.

Anchored or propped sheet piles may require pre-drilling in dense sand materials to prevent adverse
vibrations during sheet pile installation.

Other shoring methods that could be considered include bored contiguous or secant piles. Non-contiguous
or soldier pile walls are not feasible for the proposed development due to the likelihood that loose sands
would ‘flow’ through gaps between the piles.

An advantage of contiguous or secant pile wall retention systems is that they are ultimately used for the
permanent walls, whereas sheet piles would be temporary to provide retention during construction only,
therefore requiring a permanent structural wall to be constructed. Bored pile walls generally require greater
width (horizontally) for installation as compared to sheet piles and are often more expensive.

10 February 2023
Report No. 22511-001-Rev0 15

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