Finite deformation analysis of geomaterials

The mathematical structure and numerical analysis of classical small deform ation elasto-plasticity is generally well established. However, development of large deformation elastic-plastic numerical formulation for dilatant, p ressure sensitive material models is still a research area. In this paper we present development of the finite element formulation and implementation for large deformation, elastic-plastic analysis of geomateri als, Our developments are based on the multiplicative decomposition of the deformation gradient into elastic and plastic parts. A consistent Lineariza tion of the right deformation tensor together with the Newton method at the constitutive and global levels leads toward an efficient and robust numeri cal algorithm. The presented numerical formulation is capable of accurately modelling dilatant, pressure sensitive isotropic and anisotropic geomateri als subjected to large deformations. In particular, the formulation is capa ble of simulating the behaviour of geomaterials in which eigentriads of str ess and strain do not coincide during the loading process. The algorithm is tested in conjunction with the novel hyperelasto-plastic m odel termed the B material model, which is a single surface (single yield s urface, affine single ultimate surface and affine single potential surface) model for dilatant, pressure sensitive, hardening and softening geomateria ls. It is specifically developed to model large deformation hyperelasto-pla stic problems in geomechanics. We present an application of this formulation to numerical analysis of low confinement tests on cohesionless granular soil specimens recently performe d in a SPACEHAB module aboard the Space Shuttle during the STS-89 mission. We compare numerical modelling with test results and show the significance of added confinement by the thin hyperelastic latex membrane undergoing lar ge stretching. Copyright (C) 2001 John Wiley & Sons, Ltd.