Liquefaction Resistance and Steady-State Characterization of Shallow Soils within the Christchurch Central Business District

Abstract

Insights regarding the response of shallow foundation soils from building sites in the central business district (CBD) of Christchurch, New Zealand, that experienced liquefaction during the 21–211 Canterbury earthquake sequence (CES) are provided through an examination of cyclic and monotonic triaxial test data. An emphasis is placed on understanding the liquefaction resistance and large-strain steady-state response of key soils so that case histories of buildings damaged because of soil liquefaction during the CES can be developed. Comparisons of cyclic resistances from cyclic triaxial (CTX) testing and a cone penetration test (CPT)–based triggering correlation showed good agreement. Cyclic testing showed that silty sands and clean sands responded similarly in cyclic loading. However, silts tended to have flatter cyclic resistance curves. Interpretation of large-strain monotonic triaxial testing of reconstituted soil specimens provides information on the steady-state lines of the sandy soils of the CBD. The insights garnered from this laboratory testing program are critical for characterizing the Christchurch soils, as only limited cyclic testing results are available.