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Images, eqnz.chch.2010

Hotel Grand Chancellor on verge of collapse but still standing after the 6.3 magnitude quake hit Christchurch on 22 February 2011 because of concrete being poured into the lower floors.

Research papers, University of Canterbury Library

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.

Research papers, University of Canterbury Library

The 2010-2011 Canterbury earthquake sequence was extremely damaging to structures in Christchurch and continues to have a large economic and social impact on the city and surrounding regions. In addition to strong ground shaking (Bradley and Cubrinovski 2011 SRL; Bradley 2012 SDEE), extensive liquefaction was observed, particularly in the 4 September 2010 Darfield earthquake and the 22 February 2011 Christchurch earthquake (Cubrinovski et al. 2010 BNZSEE; 2011 SRL). Large observed vertical ground motion amplitudes were recorded in the events in this sequence, with vertical peak ground accelerations of over 2.2g being observed at the Heathcote Valley Primary School during the Christchurch earthquake, and numerous other vertical motions exceeding 1.0g (Bradley and Cubrinovski 2011 SRL; Bradley 2012 SDEE; Fry et al 2011 SRL). Vertical peak ground accelerations of over 1.2g were observed in the Darfield earthquake.

Images, eqnz.chch.2010

Photos taken in Parklands Library on March 31 following the February 22 earthquake. File reference: CCL-2011-03-31-New Brighton-After-The-Earthquake-NB Parkland 011 From the collection of Christchurch City Libraries

Images, eqnz.chch.2010

Photos taken in Spreydon Library on April 15 following the February 22 earthquake. File reference: CCL-2011-04-08-Spreydon-After-The-Earthquake-IMG_0466 From the collection of Christchurch City Libraries

Images, eqnz.chch.2010

Photos taken in Spreydon Library on April 15 following the February 22 earthquake. File reference: CCL-2011-04-08-Spreydon-After-The-Earthquake-IMG_0475 From the collection of Christchurch City Libraries

Images, eqnz.chch.2010

Photos taken in Lyttelton on March 20 following the February 22 earthquake. File reference: CCL-2011-03-20-After-The-Earthquake-P1110714 From the collection of Christchurch City Libraries

Images, eqnz.chch.2010

Photos taken in Lyttelton showing the demolition of various buildings following the February 22 earthquake. File reference: CCL-2011-05-20-Lyttelton-Demolition-P1120459 From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Photos taken in Spreydon Library on April 15 following the February 22 earthquake. File reference: CCL-2011-04-08-Spreydon-After-The-Earthquake-IMG_0465 From the collection of Christchurch City Libraries

Images, eqnz.chch.2010

Delivering the books. Photos taken in Redwood Library on April 8 following the February 22 earthquake. File reference: CCL-2011-04-08-Redwood-After-The-Earthquake-IMG_0436 From the collection of Christchurch City Libraries

Images, eqnz.chch.2010

Photos taken in Spreydon Library on April 15 following the February 22 earthquake. File reference: CCL-2011-04-08-Spreydon-After-The-Earthquake-IMG_0472 From the collection of Christchurch City Libraries

Images, eqnz.chch.2010

Photos taken in Spreydon Library on April 15 following the February 22 earthquake. File reference: CCL-2011-04-08-Spreydon-After-The-Earthquake-IMG_0471 From the collection of Christchurch City Libraries

Images, eqnz.chch.2010

Photos taken in New Brighton on March 31 following the February 22 earthquake. File reference: CCL-2011-03-25-New Brighton-After-The-Earthquake-NB Parkland 007 From the collection of Christchurch City Libraries

Images, eqnz.chch.2010

Photos taken in Lyttelton showing the demolition of various buildings following the February 22 earthquake. File reference: CCL-2011-05-20-Lyttelton-Demolition-P1120458 From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Photos taken in Lyttelton showing the demolition of various buildings following the February 22 earthquake. File reference: CCL-2011-05-20-Lyttelton-Demolition-P1120446 From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Photos taken in Lyttelton showing the demolition of various buildings following the February 22 earthquake. File reference: CCL-2011-05-20-Lyttelton-Demolition-P1120472 From the collection of Christchurch City Libraries.

Images, eqnz.chch.2010

Photos taken in Spreydon Library on April 15 following the February 22 earthquake. File reference: CCL-2011-04-08-Spreydon-After-The-Earthquake-IMG_0476 From the collection of Christchurch City Libraries

Images, eqnz.chch.2010

Photos taken in Lyttelton following the February 22 earthquake. Permit authorised by commanding officer HMNZS Canterbury. File ref: CCL-2011-03-05-After-The-Earthquake-P1110452 From the collection of Christchurch City Libraries

Images, eqnz.chch.2010

Photos taken in Spreydon Library on April 15 following the February 22 earthquake. File reference: CCL-2011-04-08-Spreydon-After-The-Earthquake-IMG_0473 From the collection of Christchurch City Libraries