Characterization of Shallow Soils in the Central Business District of Christchurch, New Zealand

The strong shaking experienced during multiple events of the 2010-2011 Canterbury earthquake sequence caused extensive liquefaction throughout the central business district (CBD) of Christchurch, New Zealand. The performance of structures during these events was often related to liquefaction of foundation soils. Careful sampling and triaxial testing (monotonic and cyclic) were performed on soils from key building sites in the CBD of Christchurch. High-quality test specimens could be obtained using the Dames & Moore (DM) hydraulic fixed-piston thin-walled tube sampler for most of the predominantly silty and sandy soils in the CBD. Test results indicate, though, that loose clean sand specimens were densified significantly during sampling, and, thus, the DM sampler should not be used in this type of soil deposit. Important insights regarding the cyclic response of these soils were developed through the laboratory testing. These results when combined with existing information [e.g., cone penetration test (CPT) profiles and building damage observations] provide the basis for performing dynamic analyses through the calibration of advanced soil constitutive models.