Cyclic Resistance Models for Transitional Silts with Application to Subduction Zone Earthquakes

Regression models are presented to estimate the cyclic resistance of transitional silts as an alternative to semiempirical case history and stress history and normalized engineering parameter-based models using a database of cyclic laboratory tests on intact specimens. Expressions for the plasticity index (PI) dependent semilogarithmic slope, exponent b, of the curve describing the variation of cyclic resistance ratio (CRR) and number of loading cycles and the variation of number of equivalent loading cycles with b are developed for subduction zone earthquakes alongside corresponding magnitude scaling factors for use in cyclic failure assessments (i.e., liquefaction triggering and cyclic softening) within the simplified method framework. A PI, overconsolidation ratio, and shear strain-dependent model for the variation of CRR with N is presented to estimate cyclic resistance as a function of cyclic shear strain failure criteria ranging from 1% to 10%. The suite of models can be used together or separately to facilitate assessments of cyclic failure of, or plan cyclic laboratory test programs and/or calibrate constitutive models for, transitional silts in the absence of site-specific laboratory tests.