Strengthening strategies – overview

This topic looks at strategies to strengthen and remediate ground and structures to improve seismic resilience. More detail can be found in the Ministry of Business, Innovation and Employment’s guidance Repairing and rebuilding houses affected by the Canterbury earthquakes. Section 15.3 of this guidance, which was updated in April 2015, is particularly relevant to the material in this section.

The New Zealand Geotechnical Society  also provides detailed guidance for assessing (Earthquake geotechnical engineering practice – Module 3: Identification, assessment and mitigation of liquefaction hazards) and remediating (Earthquake geotechnical engineering practice – Module 5A: Specification of ground improvement for residential properties in the Canterbury region) liquefaction-prone residential sites in the Canterbury region. While intended to assist with ground improvement following the 2010 and 2011 earthquakes, the guidance may also apply to other liquefaction-prone areas of New Zealand.

Home strengthening

Space frame in a theatre ceiling. (Sawrey Consulting Engineers)

Ground remediation

Densification techniques – including gravel rafts, dynamic compaction, rapid-impact compaction and vibro-compaction

Containment techniques – including stone columns, rammed aggregate piers and driven timber poles

Solidification techniques – including stabilised soil (off-site, rotovated and in situ soil mixing)

Strengthening residential buildings

NZS 3604-type pile foundations

Bracing foundations – including bracing perimeter foundations, bracing open pile foundations (sheet bracing and diagonal bracing) and bracing jack-stud frames

Strengthening commercial buildings  including unreinforced masonry