CHARACTERISATION OF GROUND CONDITIONS IN THE CHRISTCHURCH CENTRAL BUSINESS DISTRICT

Abstract

The magnitude Mw 6.2 earthquake of February 22nd 2011 that struck beneath the city of Christchurch, New Zealand,
\ncaused widespread damage and was particularly destructive to the Central Business District (CBD). The shaking
\ncaused major damage, including collapses of structures, and initiated ground failure in the form of soil liquefaction and
\nconsequent effects such as sand boils, surface flooding, large differential settlements of buildings and lateral spreading
\nof ground towards rivers were observed. A research project underway at the University of Canterbury to characterise
\nthe engineering behaviour of the soils in the region was influenced by this event to focus on the performance of the
\nhighly variable ground conditions in the CBD. This paper outlines the methodology of this research to characterise the
\nkey soil horizons that underlie the CBD that influenced the performance of important structures during the recent
\nearthquakes, and will influence the performance of the rebuilt city centre under future events. The methodology follows
\npost-earthquake reconnaissance in the central city, a desk study on ground conditions, site selection, mobilisation of a
\npost-earthquake ground investigation incorporating the cone penetration test (CPT), borehole drilling, shear wave
\nvelocity profiling and Gel-push sampling followed by a programme of laboratory testing including monotonic and
\ncyclic testing of the soils obtained in the investigation. The research is timely and aims to inform the impending rebuild,
\nwith appropriate information on the soils response to dynamic loading, and the influence this has on the performance of
\nstructures with various foundation forms.