Computational Model for Cyclic Mobility and Associated Shear Deformation

TLDR

In saturated clean medium‑to‑dense cohesionless soils, liquefaction‑induced shear deformation accumulates cycle‑by‑cycle, primarily during the transition from contraction to dilation near the phase‑transformation surface at low shear stress and effective confining pressure, making it difficult to predict the magnitude of permanent shear strain. The study adopts a convenient approach that defines the domain of large shear strain directly in strain‑space parameters. Cyclic shear deformation is modeled by enlarging and/or translating this strain‑space domain in deviatoric strain space, with calibration performed using laboratory sample tests and dynamic centrifuge experiments on Nevada sand at about 40 % relative density. The paper presents and discusses the detailed formulation of this computational model.

Abstract

In saturated clean medium-to-dense cohesionless soils, liquefaction-induced shear deformation is observed to accumulate in a cycle-by-cycle pattern (cyclic mobility). Much of the shear strain accumulation occurs rapidly during the transition from contraction to dilation (near the phase transformation surface) at a nearly constant low shear stress and effective confining pressure. Such a stress state is difficult to employ as a basis for predicting the associated magnitude of accumulated permanent shear strain. In this study, a more convenient approach is adopted in which the domain of large shear strain is directly defined by strain space parameters. The observed cyclic shear deformation is accounted for by enlargement and/or translation of this domain in deviatoric strain space. In this paper, the model formulation details involved are presented and discussed. A calibration phase is also described based on data from laboratory sample tests and dynamic centrifuge experiments (for Nevada sand at a relative density of about 40%).