Auckland Regulatory Review of Excavation Induced Ground Settlement

Auckland is experiencing a surge in land development including high levels of intensification. As a result of intensification, developments involving deep excavations and both temporary and permanent retaining measures are more common. Where excavations are undertaken, ground settlement around the excavation can occur and is often caused by the combined effects of consolidation due to dewatering and mechanically induced settlement behind retaining structures.

The effects of combined settlement are the most critical where excavations are undertaken close to site boundaries, near existing structures and infrastructures. If not appropriately managed or designed, damage can occur and result in unforeseen costs for remediation and legal actions. Consequently, to understand and assess the effect of deep excavations, consolidation due to dewatering and mechanically induced settlement behind temporary and permanent retaining structures have been the subject of more focus by geotechnical specialists and Auckland Council.

Auckland Unitary Plan chapters E12 (Land disturbance – District) and E7 (Taking, using, damming and diversion of water and drilling) provide regulatory requirements for an assessment of effects as a result of ground settlement. This paper explores how consolidation and mechanically induced settlement are geotechnically assessed to fulfil these requirements in Auckland.