CAM-CLAY PLASTICITY PART III - EXTENSION OF THE INFINITESIMAL MODEL TO INCLUDE FINITE STRAINS

The infinitesimal version of the modified Cam-Clay model of critical s tate soil mechanics is reformulated to include finite deformation effe cts. Central to the formulation are the choice of a hardening law that is appropriate for cases involving large plastic volumetric strains, and the use of a class of two-invariant stored energy functions approp riate for Cam-Clay-type models that includes, as special cases. the co nstant elastic shear modulus approximation as well as the pressure-dep endent shear modulus elastic model. The analytical model is cast withi n the framework of finite deformation theory based on a multiplicative decomposition of the deformation gradient. For the fully elasto-plast ic case, return mapping is done implicitly in the space defined by the invariants of the elastic logarithmic principal stretches, which requ ires the solution at each stress point of no more than three simultane ous non-linear equations. A finite element analysis of a strip footing problem is presented to illustrate a prototype example where finite d eformation effects significantly impact the predicted response. (C) 19 98 Elsevier Science S.A.