OPW052025 Report - Part 2

5.2.2         Numerical Modelling
In order to provide an estimate of footing depths and assessment of the factor of safety (FOS) against
slope instability for the proposed residence, numerical analysis has been conducted using Slope/W.
Conditions were modelled allowing for the subsurface profile encountered in the test pits and
observations on site. A surcharge of 20 kPa was applied where it is assumed residential construction will
occur (representing a maximum two storey structure or 1 m height of earth fill). A 10 kPa surcharge was
also applied to represent future live traffic loads on the driveway. Sensitivity to groundwater was also
assessed, to give an indication of the FOS under adverse, short-term conditions. It is noted that the
house site is on a high topographical location, and the driveway along the crest of a ridgeline, therefore
the development of consistent long-term groundwater is unlikely.
An extract from the analysis is presented below in Text Figures 12 (proposed house) and 13 (nominal
section through proposed driveway.




      Text Figure 12: Extract from Slope/W Analysis (Section A-A'- including adverse groundwater
                                              condition)




Geotechnical Investigation & Slope Stability Assessment
9 April 2025 | 25050-001-Rev0                                                                            16