Bounding surface rotational hardening model for overconsolidated clay accounting for evolving fabric anisotropy

Abstract

Soil is inherently anisotropic owing to the sedimentation process under gravity and is generally under anisotropic stress state in the field. To reflect the influence of anisotropic consolidation, rotational hardening (RH) is favorably used in constitutive models, mimicking in-situ stress conditions. However, most of the existing models do not account for the inherent anisotropy of clays under isotropic stress state as well as the interplay between the fabric and loading direction, and the corresponding initial yield surface is assumed to be oriented along the hydrostatic axis. Furthermore, as the rotational angle is usually deemed as the clayed soil's anisotropy measure, a critical yield surface without rotation appears to contradict the highly anisotropic fabric at critical state. In this study, an anisotropic bounding surface model that incorporates RH and fabric anisotropy is formulated to simulate the behavior of overconsolidated (OC) clay subject to different consolidation histories, while addressing the aforementioned inconsistency issue. During the loading process, both fabric anisotropy and rotational angle evolve continuously based on their respective evolution rules. Fabric anisotropy evolves to the critical state when the rotational angle returns to zero, satisfying the anisotropic critical state theory (ACST). In addition, the model employs an anisotropic elasticity to consider the influence of the initial fabric at a low-stress level. The predictive capacity of the model can be demonstrated by simulating several compression and extension tests on clay over a wide range of overconsolidation ratios (OCRs) and anisotropic consolidation stress ratios under both drained and undrained conditions.

WITHDRAWN: Effect of matric suction on stress-induced anisotropy behavior of unsaturated clay

“…By summarizing the stress-strain relationships of unsaturated clay specimens under various matric suctions, the critical state parameter M' (effective stress at critical state) was obtained for unsaturated clay under different stress paths. Numerous studies [1,12,39,53] indicate that that the critical state stress ratio M' of unsaturated clay remains unchanged under different matric suctions. Figure 10 depicts the critical state line (labeled CSL on the graph) of saturated clay in the p' -q plane.…”

A multifidelity neural network (MFNN) for constitutive modeling of complex soil behaviors

“…This is especially evident for heavily over-consolidated clays, whose response characteristics such as strain softening, dilatancy, and peak stress ratio cannot be reasonably described by the MCC model. Hence, some studies have introduced new theories such as the multisurface plasticity, 44 bounding surface plasticity, 7,45,46 and subloading surface plasticity 47 to better simulate the mechanical behaviors of over-consolidated clays at a cost of increased model complexity.…”

“…Although the Cam‐clay models have been widely accepted, they are only strictly applicable to saturated normally consolidated remolded clays. More advanced models based on critical state soil mechanics have been developed to accommodate different soil types and general stress paths 4–7 . Despite that these mathematical models formulated under the framework of plasticity are successful in reproducing many salient features of soil shear behaviors, they bear inherent limitations in generalizability.…”

“…More advanced models based on critical state soil mechanics have been developed to accommodate different soil types and general stress paths. [4][5][6][7] Despite that these mathematical models formulated under the framework of plasticity are successful in reproducing many salient features of soil shear behaviors, they bear inherent limitations in generalizability. As reduced-order models, they are constructed based on certain assumptions and simplifications, thus only applicable to a specific soil type and/or loading condition.…”