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