A Unified Hardening Constitutive Model For Structured Soil Based On Rotational Hardening

Structure and induced anisotropy exist widely in natural clay.The structure will make the undisturbed soil have higher strength than the remolded soil,but with the stress and deformation,the structure will be destroyed gradually.And induced anisotropy will change the modulus of soil in all directions during the process of deformation.When both of them act at the same time,the stress-strain relationship of soil will be affected.This phenomenon should be paid attention to in the actual project,otherwise,it will increase the risk.Therefore,it is of great significance to establish a constitutive model that can consider the effects of both structural and induced anisotropy.In this paper,on the basis of the unified hardening model of structured soil,introduced rotation hardening,add a rotational symmetry axis to the yield surface of the model,and extend the unified hardening model of structured soil to the unified hardening model of structured soil based on rotation hardening to induce anisotropy.On this basis,based on the SMP criterion,applied the transformation stress method to extend the model to three-dimensional stress space.The evolutions of the model shows that the model can smoothly and continuously describe the coupling effect of structure and rotational hardening in compression and shear loading.Comparing the test data and the model prediction of structured clay,it shows that the unified hardening model of structured clay based on rotation hardening can reasonably predict the mechanical behaviors of structured clay in isotropic compression,drained shearing triaxial compression and undrained shearing triaxial compression.An Umat subroutine of the presented model for Abaqus is written and its validity is verified by simulation.