This paper presents results from effective stress analyses on four Christchurch sites under the shaking induced by the 22 February 2011 Christchurch earthquake. The four sites have similar characteristics in terms of critical layers but differ significantly with regard to the composition of soils within the top 10 m of the deposit, with the main distinctive feature being either vertical continuity or discontinuity of liquefiable materials. These differences are reflected in varying levels of severity of surface liquefaction manifestation observed at the four sites during the 2010-2011 Canterbury earthquakes. In contrast to the CPT-based simplified liquefaction triggering evaluation which predicts liquefaction of the shallow critical layer for all four sites, the effective stress analyses effectively explain their different performance during the February 2011 earthquake. In particular, the effective stress analyses predict different combinations of depth-thickness-severity of liquefaction between the four sites and demonstrate that system response effects related to dynamic cross-interaction between different layers in the deposit and pore water redistribution and water flow play a predominant role on the occurrence and severity of liquefaction at a given depth. Findings from this study emphasize the need to consider system-response of deposits when evaluating liquefaction and its damage potential.
展开▼
