A Nonorthogonal Elastoplastic Model for Overconsolidated Clay

Abstract

The constitutive model in geotechnical engineering plays a critical role, driving the need for ongoing research and improvement. In this study, by utilizing a single yield curve and only one hardening parameter, a nonorthogonal elastoplastic (NOEP) constitutive model for the overconsolidated (OC) clay is established within the framework of the NOEP model. The nonorthogonal plastic flow rule, based on the Riemann–Liouville fractional derivative, was employed to determine the plastic flow direction, which is nonorthogonal to the improved yield curve. Furthermore, a novel hardening parameter is proposed to capture the magnitude of plastic strain increment for OC clays. This is achieved by comparing deformation behaviors in OC clays with two distinct degrees of overconsolidation. Additionally, it is further enhanced by the integration of a newly proposed potential stress ratio. The proposed model requires only eight parameters, and its performance is evaluated by its predictions with test results for OC clays subjected to drained or undrained triaxial stress conditions. This study is expected to offer valuable insights and a better approach toward understanding and capturing the deformation behaviors of OC clays.