slope stability

Integra Partnerships                                                                               22340-001-Rev0
                                                                                                14 September 2022




                            Text Figure 9: 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.

3.5     Retaining Walls
Retaining structures must be founded as per the recommendations in Section 3.4 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 4 may be adopted for retaining wall design. The values in Table 4 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 2.
Table 2: 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            28                 0.36                    0.53               2.77
 Sands
 Medium Dense (or
                               18            32                 0.31                    0.47               3.25
 Denser) Sands
 Future Fill                    *             *                  *                         *                *
Note:    *      depends on fill material type and level of compaction




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