EVENTO
A modified form of Terzaghis effective stress principle for unsaturated expansive clays rigorously derived from micro-structure
Tipo de evento: Seminário LNCC
A three-scale model is proposed to describe electro-chemo-mechanical couplings in unsaturated swelling clays characterized by two porosity levels (nano and micro pores). The nano-scale portrait consists of charged clay particles saturated by a binary monovalent aqueous electrolyte solution of completely dissociated sodium chloride ions. Local ion distribution and electric potential are governed by the Poisson-Boltzmann problem. At the micro-scale, the system is represented by swollen clay clusters separated from each other by micro-pores filled by a mixture of bulk water and air. The macroscopic description is obtained by the self consistent homogenization method of periodic structures. Under mechanical equilibrium characterized by the competition between disjoining forces of electro-chemical nature and capillary attraction mechanisms, a novel form of the effective stress principle is derived in the asymptotic limit of scale separation. In addition to the contact stress between particles, the novel form includes a three-scale representation of the swelling pressure along with a generalized capillary Bishop component-type which can be computed from micromechanical-basis. By discretizing the local Poisson-Boltzmann problem we build-up a constitutive law for the effective stress as a function of water saturation and salinity for prescribed macroscopic strain and a collection of inter-particle distances. The theory is applied to simulate an equilibrium experiment of a clay liner subject to an external constraint characterized by a given overburden. Numerical results show the potential of the multiscale approach in capturing the complex features of the expansive medium.
Data Início: 08/10/2012 Hora: 14:00 Data Fim: Hora: 15:30
Local: LNCC - Laboratório Nacional de Computação Ciêntifica - Auditorio A
Comitê Organizador: Julia Mainka - - LNCC - mainka@lncc.br
