Multimechanism elasto-plastic model for soils

A multiple-mechanism elasto-plastic model for soils applicable to general three-dimensional stress states and cyclic loadings is presented. The model uses the concept of mobilized friction angles to define yielding. In stress space, the postulated yielding mechanisms define an elastic domain whose boundary is, in general, nonsmooth and possesses comers. Theoretical and computational aspects of the model are discussed in detail. Numerical implementation of the model is performed using the cutting plane algorithm. The model accuracy is demonstrated using triaxial soil test data and previously determined material parameters. The model is accurate in characterizing soil behavior and able to capture both compactive and dilative responses of soil. Also, the accuracy of the stress-point algorithm used for the update of the stress state is analyzed and found to be acceptable. Finally, the model is used to compute the response of a semi-infinite saturated soil deposit consisting of loose and dense layers subjected to earthquake base excitation. Resulting changes in pore fluid pressure, accompanied by changes in vertical effective normal stress, are illustrated.