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UNDERSTANDING LIQUEFACTION THROUGH APPLIED MECHANICS (2011)
Soil liquefaction is conventionally evaluated through an empirical framework based on accumulated experience from case histories - the "NCEER Method". However, the empirical framework contains inconsistent physics and characterizations that are unrelated to modern understanding of soil constitutive behaviour. This paper considers cyclic mobility within the context of a modern constitutive model, NorSand, to illustrate a proper approach to evaluating the effect of soil type ('fines content'), stress level and initial stress state on liquefaction. A two-pronged approach is used with soil state in situ being inferred from the CPT, while the cyclic strength-state relationship is computed using measurable, standard, soil properties (compressibility, etc). Computed liquefaction resistances are consistent with the case history record, but the approach now offers understanding as to how that experience should be extrapolated to other situations. And, contrary to what might be expected, the proposed approach turns out to be both straightforward and readily done in engineering practice - the calculations run in a spreadsheet. Of course, it now becomes necessary to measure soil compressibility and elastic shear modulus.
5th International Conference on Earthquake Geotechnical Engineering, January 2011, 10-13, Santiago, Chile
Golder Associates, Vancouver, Canada