Liquefaction of sandy silt and silt from cyclic DSS testing

John P. Sully, Ender J. Parra

In the proceedings of: GeoMontréal 2013: 66th Canadian Geotechnical Conference; 11th joint with IAH-CNC

Session: Soil and Rock Mechanics IV

ABSTRACT: Generally accepted methods used to evaluate the potential for liquefaction have been developed primarily for clean sands or silty sands with up to about 35% fines content. The method is based on the interpretation of in situ penetration test data in sand to estimate the cyclic resistance ratio and compare that with the cyclic stress ratio induced by the design earthquake ground motions. As the fines content in sand increases, the in situ penetration test data is corrected in an attempt to compensate for the effect of fines content on the penetration resistance. Correction methods have been proposed for both SPT and CPT data. Where the silt content of sand is higher than 35%, or the soil can be classified as a non-plastic silt, the correction factors do not appear to adequately reflect the increased resistance to liquefaction. Under these conditions, the generally accepted procedure is to base the assessment on laboratory tests. The paper presents the results of a series of cyclic simple shear tests performed on silty sands and silts from profiles primarily based in the Lower Mainland of British Columbia. The test results confirm that the increased resistance to liquefaction may not be adequately represented by the correction methods proposed for in situ penetration data. Several other aspects particular to the behaviour of sandy silt and silt are also highlighted based on cyclic DSS testing.

Please include this code when submitting a data update: GEO2013_160

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