A bounding surface model for anisotropically overconsolidated clay incorporating thermodynamics admissible rotational hardening rule

Abstract

Summary A bounding surface model is formulated to simulate the behavior of clays that are subject to an anisotropic consolidation stress history. Conventional rotational hardening is revisited from the perspective of thermodynamics. As the free energy cannot be accumulated infinitely upon critical state failure, the deviatoric back stress must vanish. This requires the rotated yield surface to be turned back to eventually align on the hydrostatic axis in the stress plane. Noting that most of the previous propositions violate this restriction, an innovative rotational hardening rule is formulated that is thermodynamically admissible. The bounding surface framework that employs the modified yield surface is applied to simulate elastoplastic deformations for overconsolidated clays, with which the overprediction of strength on the “dry” side can be greatly improved with reasonable results. Other important features, including contractive or dilative response and hardening or softening behavior, can also be well‐captured. It has been shown that the model can simulate three types of reconstituted clays that are sheared with initial conditions over a wide range of anisotropic consolidation stress ratios and overconsolidation ratios under both triaxial undrained and drained conditions. Limitations and potential improvement of the model regarding the fabric anisotropy at critical state have been discussed.

Adaptive anisotropic constitutive modeling of natural clays

“…Jiang et al 38 . presented RH rules as a function of plastic volumetric strain increment, Chen and Yang 17 introduced a RH rule by incorporating only plastic deviatoric strain increment. Involving both components of plastic strain increment in the evolution of anisotropy is another option that can be found in the works of Pestana and Whittle 19 , Wheeler et al 36 ,.…”

“…Yu 18 showed that models using associated flow rule fail to predict the undrained response of normally consolidated undisturbed clays with softening and pre‐failure peak strengths. Taking this point into account, several recently developed models employ the non‐associated flow rule in their formulation 16,17,37–39,52 …”

“…A popular approach in considering the effects of inherent anisotropy within an elastoplastic modeling framework is development of elastoplastic soil constitutive models that involve inclined yield curves 25–29 . This methodology for representing the inherent anisotropy has its roots in the works of Sekiguchi and Ohta, 30 and Hashiguchi, 31 and were subsequently followed by other researchers 17,21,32–40 . In these works, the inclined YS is either fixed 30,41 or variable by adopting a rotational hardening (RH) rule to simulate the development or erasure of anisotropy during plastic straining 17,36–39,42–46 .…”

“… 39 introduced constitutive models which adopt both volumetric and deviatoric plastic strain increments in their RH rules. Defining the RH rule as a function of only deviatoric plastic strain increment has also been examined in the work of Chen and Yang 17 .…”

Prediction and numerical simulation of the face‐slab extrusion damage of Dashixia concrete faced rock‐fill dam

“…A new parameter that controls the shape of the yield surface was introduced in the model to fit the undrained shear strength. Chen and Yang 27 proposed a bounding surface model for overconsolidated clays to simulate elastoplastic deformations. With a modified yield surface, the model can capture the contractive or dilative response and hardening or softening behavior under different conditions.…”