Case study review of seismically induced land damage mitigation using stone column ground improvements in Christchurch, NZ

The major earthquake sequence from 2010 to 2011 caused significant damage to residential and commercial properties in Christchurch, New Zealand. Damage to major civil infrastructure, as a result of seismically induced liquefaction, lateral spreading and the associated settlements is often considered to be severe. The rebuild of infrastructure within the Christchurch area required significant ground improvement works to reduce the potential for seismically induced land damage from future earthquake events.

This paper will provide a background on the effects of seismically induced land damage and detail the use of stone column ground improvement works to reduce or mitigate liquefaction potential through ground densification. Three case studies within the Christchurch area where stone columns have been used for ground densification, with differing site conditions and installation methods will be critically reviewed and appraised, including a review of the design assumptions and lessons learned from observing construction works. The theoretical effectiveness of stone column ground improvements at these sites will then be analysed and discussed using construction compliance testing. The paper will then discuss key advantages and shortcomings of stone column ground improvements in differing soil conditions found in Christchurch and how this may apply to other parts of New Zealand.