slope stability · MCU22/0172

Integra Partnerships                                                                             22339-001-Rev0
                                                                                              13 September 2022

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
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 be founded such that they are not adversely affected by or affect any adjacent
excavations, trenches, retaining walls, or in ground structures that are not designed to support building loads
(e.g. sewer along front boundary). Footings should be founded 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.




                           Text Figure 10: Footing depth required to prevent undermining

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.
Should bored piles be adopted, it is essential that the piling contractor have a ‘mud bucket’ or similar to
enable clean out of the pile bases. It is recommended that bored pile sockets 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.




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