RFI - Revised Geo-Environmental Investigation · MCU25/0020

Design for temporary and permanent retaining structures could be carried out using the pressure
distribution applicable to the wall type and based on the parameters listed in Table 4. These values do
not include allowance for hydrostatic pressures nor transient (e.g. construction) or adjacent footing
loadings.

Table 4: Retaining Structure Design Parameters

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

        Firm Clay                17             23         0.44              0.61               2.28


        Loose Sand               17             30         0.33               0.5               3.0


 Medium Dense Sands              18             34         0.28              0.44               3.54

  Dense to Very Dense
                                 19             38         0.24              0.38               4.20
         Sands

The advice of a suitably experienced, specialist contractor must be sought regarding feasibility, design
and installation of the preferred retention and dewatering system for this site. It will be necessary to
conduct numerical analysis to optimise the retention system. Temporary and permanent retention
design must be designed and certified by a suitably qualified and experienced RPEQ engineer.


6.4          Building Foundations
6.4.1        Settlement Analysis
For the proposed two storey building with double level basement, SCG has indicated that contact
pressures beneath a possible raft slab would be in the order of about 55 kPa. To assess the geotechnical
feasibility of supporting the building on a stiffened raft footing system at basement floor level,
settlement analysis has been carried out using Settle 3D. The analysis considered a flexible footing
founded on medium dense sand at about 7 m BGL and assumed that, if required, over-excavation and
replacement of any loose/firm materials would be undertaken near the basement level, as outlined in
Section 6.2.1. Our analysis indicates that elastic and consolidation settlements would be in the order of
the values provided in Table 5 overleaf.




Geo-environmental Investigation Proposed Residence
4 June 2025 | 25040-001-Rev1                                                                               14