On Implicit Integration In The Anisotropic Bounding-surface Plasticity Model

The anisotropic bounding-surface plasticity model based on a newly proposedhardening rule was developed to predict the cyclic behaviours of embedded offshorestructures in a marine environment. Within a critical state framework, the model haswide representation, which adopted a rotated bounding surface to account for theinitial anisotropy induced by anisotropic consolidation and introduced the damageparameter to reflect cyclic degradation in the stiffness and strength of soil. However,the model in thep qstress space can not reflect the strength and deformation ofsoil in true stress states. Therefore, with reasonable integration algorithm, thethree-dimensional model is developed in the finite element software for numericalcomputation.For achieving the calculation of the model in ABAQUS, the work has been doneas following. First, based on the lacking of monotonic loading simulation with thedeveloped model, the numerical calculations of the undrained triaxial test for Kaolinclay, remodeling Weald clay and the San Francisco Bay mud is implemented. It isvalidated that the model can preferably reflect the response of deformation andstrength for monotonic loading. Then, a fully implicit integration scheme in thethree-dimensional model of the generalized Mises criterion for cyclic behaviors ofsaturated clay is presented by modifying the conventional implicit return mappingalgorithm, and developed into ABAQUS. The numerical simulations of the undrainedtriaxial tests both for isotropic and anisotropic consolidated Kaolin Clay are carriedout with variable strain increments. By comparing with the test data, the rationality,robustness and the accuracy of the new fully implicit integration for the boundingsurface plasticity model are verified. At last, due to the limitation of the extendedMises method, the model is generalized using transformed stress method. The resultsof simulations of monotonic and cyclis loading show that the generalized anisotropicconstitutive model using the SMP method can precisely evaluate the strength anddeformation characteristics of theK0consolidation soils.