Christchurch Eye Surgery Building Extension

 THE BRIEF 

Christchurch Eye Surgery, was constructed in 2012 following the Canterbury Earthquake Sequence. The site is classified as TC3 indicating a high risk of liquefaction-induced settlement.

Riley carried out geotechnical investigations and recommendations for a foundation system comprising a waffle slab over a geogrid-reinforced gravel raft.

In 2024, a building extension to the facility was proposed, aiming to double the building footprint and expand surgical and patient care capabilities. Riley was re-engaged to complete further geotechnical investigations and provide updated recommendations. A key objective was to develop consistent geotechnical conditions to minimise differential performance between the existing and new foundation systems, as the extension will be structurally integrated with the existing building.

Key challenges:

• Foundation stiffness consideration: To achieve uniform structural response between new and existing foundations, soil spring stiffness values were derived to enable the entire foundation system to perform cohesively.

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• Protection of existing structure: The construction methodology needed to be carefully thought out to minimise undermining the existing building.