FAILURE PREDICTIONS OF PARTIALLY SATURATED QUASI BRITTLE MATERIALS WITH A THERMODYNAMICALLY CONSISTENT GRADIENT POROPLASTIC THEORY

G.J. ETSE; J.L. MROGINSKI

Raleigh, North Carolina

Conferencia; 12th U.S. National Congress on Computational Mechanics (USNCCM12); 2013

USACM

The thermodynamically consistent non-local gradient theory for porous media proposed by the authors is considered to evaluate failure behavior of partially saturated quasi brittle materials in engineering like soils and concrete. In this constitutive theory the state variables are the only one of non-local characters while the local and non-local stress dissipations (within the porous media and along its boundary) are formulated based on thermodynamic considerations. A fundamental aspect in this formulation is the inclusion of two characteristic lengths, one for the solid phase and the other for the porous phase. To avoid the unrealistic failure diffusion that is inherent to the gradient plasticity theory, the characteristic lengths in this constitutive theory are formulated in terms of the acting pressure (in the solid and porous phases) as well as of the saturation degree of the porous phase. After presenting the foundation of the constitutive theory, the attention focuses on the predictions of localized failure modes in the form of discontinuous bifurcation. To this end, spectral analyses of the localization indicator for drained and undrained conditions are performed. Finally, the numerical implementation of the constitutive theory in the framework of a new FE formulation with 8 nodes and selective C1 and C0 interpolation functions for the internal variables and the kinematic fields, respectively, is discussed. The numerical results demonstrate the capabilities of the constitutive theory and numerical tools to predict failure processes of partially saturated quasi brittle materials under both, drained and undrained conditions.