Comparisons In The Cyclic Direct Simple Shear Response Of Two Sands From Christchurch, New Zealand

During the 2010-2011 Canterbury earthquake sequence, the Canterbury region and the city of Christchurch, New Zealand, were profoundly affected by liquefaction in natural sand and silty sand deposits. Following these events, comprehensive characterization studies of these soil deposits have been performed including in situ geotechnical tests (boreholes, CPT, V-s measurements) and cyclic triaxial tests on undisturbed and reconstituted (moist tamped) specimens. This paper presents results from a series of undrained cyclic direct simple shear (DSS) tests on two sands from Christchurch. Soil specimens were reconstituted with the water sedimentation technique in order to yield a fabric resembling that of fluvial soil deposits. The use of DSS device aims to better reproduce the seismic response of free-field level ground deposits. Liquefaction resistance curves observed in the DSS tests are comparatively presented for the two sands, and their relation to the liquefaction resistance determined from empirical triggering relationships is discussed.