Post February 22 Earthquake Damage PWS-2011-03-09-DSC9951
In the period between September 2010 and December 2011, Christchurch was shaken by a series of strong earthquakes including the MW7.1 4 September 2010, Mw 6.2 22 February 2011, MW6.2 13 June 2011 and MW6.0 23 December 2011 earthquakes. These earthquakes produced very strong ground motions throughout the city and surrounding areas that resulted in soil liquefaction and lateral spreading causing substantial damage to buildings, infrastructure and the community. The stopbank network along the Kaiapoi and Avon River suffered extensive damage with repairs projected to take several years to complete. This presented an opportunity to undertake a case-study on a regional scale of the effects of liquefaction on a stopbank system. Ultimately, this information can be used to determine simple performance-based concepts that can be applied in practice to improve the resilience of river protection works. The research presented in this thesis draws from data collected following the 4th September 2010 and 22nd February 2011 earthquakes. The stopbank damage is categorised into seven key deformation modes that were interpreted from aerial photographs, consultant reports, damage photographs and site visits. Each deformation mode provides an assessment of the observed mechanism of failure behind liquefaction-induced stopbank damage and the factors that influence a particular style of deformation. The deformation modes have been used to create a severity classification for the whole stopbank system, being ‘no or low damage’ and ‘major or severe damage’, in order to discriminate the indicators and factors that contribute to ‘major to severe damage’ from the factors that contribute to all levels of damage a number of calculated, land damage, stopbank damage and geomorphological parameters were analysed and compared at 178 locations along the Kaiapoi and Avon River stopbank systems. A critical liquefiable layer was present at every location with relatively consistent geotechnical parameters (cone resistance (qc), soil behaviour type (Ic) and Factor of Safety (FoS)) across the study site. In 95% of the cases the critical layer occurred within two times the Height of the Free Face (HFF,). A statistical analysis of the geotechnical factors relating to the critical layer was undertaken in order to find correlations between specific deformation modes and geotechnical factors. It was found that each individual deformation mode involves a complex interplay of factors that are difficult to represent through correlative analysis. There was, however, sufficient data to derive the key factors that have affected the severity of deformation. It was concluded that stopbank damage is directly related to the presence of liquefaction in the ground materials beneath the stopbanks, but is not critical in determining the type or severity of damage, instead it is merely the triggering mechanism. Once liquefaction is triggered it is the gravity-induced deformation that causes the damage rather than the shaking duration. Lateral spreading and specifically the depositional setting was found to be the key aspect in determining the severity and type of deformation along the stopbank system. The presence or absence of abandoned or old river channels and point bar deposits was found to significantly influence the severity and type of deformation. A review of digital elevation models and old maps along the Kaiapoi River found that all of the ‘major to severe’ damage observed occurred within or directly adjacent to an abandoned river channel. Whilst a review of the geomorphology along the Avon River showed that every location within a point bar deposit suffered some form of damage, due to the depositional environment creating a deposit highly susceptible to liquefaction.
As a result of the Canterbury earthquakes, over 60% of the concrete buildings in the Christchurch Central Business District have been demolished. This experience has highlighted the need to provide guidance on the residual capacity and repairability of earthquake-damaged concrete buildings. Experience from 2010 Chile indicates that it is possible to repair severely damaged concrete elements (see photo at right), although limited testing has been performed on such repaired components. The first phase of this project is focused on the performance of two lightly-reinforced concrete walls that are being repaired and re-tested after damage sustained during previous testing.
An entry from Ruth Gardner's blog for 24 June 2012 entitled, "Reducing Rooftop Risks".
An entry from Ruth Gardner's blog for 17 January 2012 entitled, "Loopy Lights".
An entry from Ruth Gardner's blog for 7 December 2012 entitled, "Aggravating Arson".
An entry from Ruth Gardner's blog for 5 June 2011 entitled, "Cul-de-sac Cricket".
An entry from Ruth Gardner's blog for 23 July 2011 entitled, "Piko Plastered".
A photograph captioned by Paul Corliss, "River Road, Avonside".
A photograph captioned by Paul Corliss, "River Road, Avonside".
A photograph captioned by Paul Corliss, "River Road, Avonside".
A photograph of the earthquake damage to a block of buildings on Worcester Street. One of the buildings has also suffered damage from a fire caused by the 4 September 2010 earthquake.
Photo of damage to Waimakariri River South Branch(primary bank), taken by John Dore, 8 September 2010.
A close up of the damaged stonework of Christ Church Cathedral. The upper part of the front wall has crumbled leaving the inside space exposed. Steel bracing has been placed against the wall to limit further damage.
Damage to the Lyttelton Port. In the background the HMNZS Canterbury can be seen, just returned from a trip to Wellington to resupply.
Photo of damage to Waimakariri River South Branch(primary bank), taken by John Dore, 8 September 2010.
Photograph captioned by Fairfax, "Earthquake damage in central Christchurch after a 6.3 earthquake. Sue Spigel, Christchurch Cathedral artist-in-residence, climbs out of the damaged cathedral".
A close up of the damaged stonework of Christ Church Cathedral. The upper part of the front wall has crumbled leaving the inside space exposed. Steel bracing has been placed against the wall to limit further damage.
For the first time in November 2011, Christchurch residents finally had the opportunity to see the earthquake-damaged city centre on the Red Zone bus tours organised by CERA. Damage to buildings can be seen out the window.
Photo of damage to mobiles shelves in Records Office, taken by Glenda Duffell on 6 September 2010.
A photograph of earthquake-damaged buildings along Manchester Street near Struthers Lane. The front of the buildings have crumbled, the bricks falling onto the footpath in front, damaging the awnings.
Photo of damage in Kaiapoi on tour with Hon Nick Smith, taken by Ian Heslop, 10 September 2010.
An entry from Jennifer Middendorf's blog for 8 September 2010 entitled, "Exhaustion and fear".
A story submitted by Hilary Lakeman to the QuakeStories website.
An entry from Ruth Gardner's blog for 3 March 2011 entitled, "Day 10, pm - inside the Christchurch cordon".
An entry from Ruth Gardner's blog for 11 September 2010 entitled, "One Week After".
An entry from Ruth Gardner's blog for 26 February 2011 entitled, "Shaken City".
An entry from Ruth Gardner's blog for 27 February 2011 entitled, "Scenes Around the Barbadoes Street Bridge".
A story submitted by Tim Kerr to the QuakeStories website.
A story submitted by Sarah Dreyer to the QuakeStories website.