ABOUT THE PORE PRESSURE INFLUENCE IN THE FAILURE PROCESSES AND LOCALIZATION ANALYSIS OF PARTIALLY SATURATED SOIL BASED ON A GRADIENT POROPLASTIC THEORY

J.L. MROGINSKI; G.J. ETSE

Buenos Aires

Conferencia; 15th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, XV PCSMGE 2015; 2015

Argentinian Geotechnical Engineering Society (SAIG)

The strain localization problem of frictional cohesive porous materials like partially saturated soils is strongly related to water saturation degree and the softening mechanical behavior. In this situation a pathological dependences of the FE numerical solution is observed with respect to the size and orientation of the considered spatial discretization. Therefore, to realistically and objectively describe the dramatic change from diffuse to localized failure mode or from ductile to brittle ones, accurate constitutive theories and numerical approaches are required. In this article, a non-local gradient poroplastic model proposed by (Mroginski and Etse, Int. J. Solids Struct., 51: 1834-1846, (2014)) for partial saturated media based on thermodynamic concepts is considered. The non-local softening formulation of the proposed constitutive theory incorporates the dependence of the gradient characteristic length on both the governing stress and hydraulic conditions to realistically predict the size of the maximum energy dissipation zone. The material model employed in this work to describe the plastic evolution of porous media is the Modified Cam Clay, which is widely used in saturated and partially saturated soil mechanics. To evaluate the dependence of the transition point between ductile and brittle failure regime in terms of the hydraulic and stress conditions, the localization indicator for discontinuous bifurcation is formulated for both drained and undrained conditions, based on wave propagation criterion. Numerical results are presented and discussed to demonstrate the capabilities of the proposed theory to simulate failure behaviour of saturated media.