7 Pentlow Place – Residential


Design and construction completed.
Ground improvement comprised 0.6 m diameter stone columns at 1.6m spacing, with an ‘Area Replacement Ratio’ of 13%.
Ground improvement was carried out to between 4.5 to 6m below ground level over a gravel bed.
Ground improvement removed 95% vertical settlement for a 25-year earthquake event and 85% of vertical settlement for a 500-year event.


Ground improvement was adopted for this high-spec two-storey residential dwelling to reduce predicted earthquake vertical settlement to within TC2 category limits. The shallow gravel layer made stone column ground treatment an economical ground treatment option for the proposed dwelling. The reasonably clean sandy soils overlying the gravel layer, responded very well to a lower ‘arr’ value of 13 % compared to MBIE guidelines, recommending 18 to 20%.