Reference Document - Geotechnical Investigation Report - DBW24/0090 & RAP24/0025

                Rebecca Stead                                                                                        20248-001-Rev0
                                                                                                                   3 September 2020

                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.

                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 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.

                Table 1: Retaining Structure Design Parameters

                                                                                 Lateral earth pressure coefficients
                                               Unit      Friction
                  Retained material          weight      angle Ø
                                                                             Ka                     Ko
                                             (kN/m3)        (°)                                                        Kp
                                                                      (Cantilever wall)     (Non-yielding wall)


                  Very Loose/ Loose
                                                17          30              0.33                   0.50                3.00
                  Sands


                  Medium Dense (or
                                                18          34              0.28                   0.44                3.54
                  Denser) Sands


                  Future Sand Fill(Note 1)      17          32              0.31                   0.47                3.25

                  Note:
                      1)    For sand fill placed and compacted as recommended in Section 4.2 above.




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Document Set ID: 23080488
Version: 1, Version Date: 27/06/2024