ECM_22343520_v1_Geotechnical Investigation · 132000.200173.1

                                          PROPOSED RENOVATIONS
                                          2 ARAKOON CRESCENT, SUNSHINE BEACH

            6.2.2         Footing Design
            Should any of the existing structural elements remain, the residence and ancillary structures must not exert
            additional load on these elements, unless assessed and approved by a structural RPEQ, who must also
            confirm the existing footings and structural members have sufficient capacity to carry additional loads
            imposed by the development.
            No design loadings were available at the time of reporting. Footings for the proposed residence and any
            ancillary structures (e.g. retaining walls, pool etc.) must penetrate through any fill materials and unsuitable
            natural soils (i.e. very loose to loose sands) to found at least 1 m into medium dense (or denser) natural
            sands. High-level footings may be possible in areas of deeper excavation if medium dense (or denser) sands
            are exposed at or near the subgrade. This would be subject to an assessment by a suitably qualified and
            experienced geotechnical RPEQ. High-level footings, so founded, could be designed using a maximum
            allowable bearing pressure of 100 kPa.
            Elsewhere, based on the ASI boreholes, pile founding depths between about 4 m and 5 m BGL (existing
            ground levels) are anticipated. Deeper pile depths may be necessary subject to assessment of building loads
            at the detailed design stage. To confirm founding depths, deeper borehole drilling should be undertaken
            following partial or complete demolition of the existing structures to assess subsurface conditions in the
            eastern part of the site.
            Excluding the eastern retaining wall, steel screw piles are considered to be an appropriate footing option for
            the proposed development. For the eastern boundary retaining wall to achieve the required unfactored shear
            resistance of 100 kN/m it is envisaged that steel reinforced concrete bored piles or grout-injected CFA piles
            (or similar) will be required. Steel reinforced concrete bored piles would require the use of sacrificial liners
            (e.g. Formatube) to prevent caving of the upper sands. Construction water loss would also need to be
            carefully monitored and controlled should CFA piles be adopted. The capacity of the piles to achieve this
            shear capacity or an equivalent amount should be checked as part of the structural design (lateral capacity).

            If steel screw piles are adopted for the main residence and internal walls, 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.

            Ultimately, the advice of a specialist piling contractor should be sought regarding pile design and
            construction. However, where steel screw piles are adopted site specific load testing and the results of this
            geotechnical investigation should be considered by the structural engineers in validating any generic torque
            to capacity ratios provided as part of the proposed design. An assessment of potential vibration effects on
            nearby structures and monitoring requirements should also be included.

            Footing design should also account for potential soil reactivity to be equivalent to Class M. It should be noted
            that the placement of reactive clay may result in a more significant equivalent site classification, such as Class
            H1 (or higher).
            All footings should found such that they are not adversely affected by any adjacent excavations, batter slopes,
            trenches, or retaining walls that are not designed to support building loads. Footings adjacent to any fill batter
            crests should be deepened to found below the toe of the batter. Footings should found at least below a plane
            extending 1 m horizontally from the base of trenches/underground services/excavations/retaining walls, then
            rising up at 1V:1H, as illustrated in Text Figure 13 overleaf.




             24 February 2023
             Report No. 22484-001-Rev0                              16
Document Set ID: 22343520
Version: 1, Version Date: 16/03/2023