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A micromechanical‐based elasto‐viscoplastic model for the Callovo‐Oxfordian argillite: Algorithms, validations, and applications
Author(s) -
Zeng Tao,
Shao JianFu,
Yao Yao
Publication year - 2019
Publication title -
international journal for numerical and analytical methods in geomechanics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.419
H-Index - 91
eISSN - 1096-9853
pISSN - 0363-9061
DOI - 10.1002/nag.3006
Subject(s) - viscoplasticity , constitutive equation , homogenization (climate) , creep , finite element method , plasticity , biot number , moduli , materials science , geotechnical engineering , computer science , structural engineering , geology , mechanics , engineering , composite material , physics , biodiversity , ecology , quantum mechanics , biology
Summary For a potential geological barrier of high‐level radioactive waste repositories in France, the long‐term mechanical behavior of the Callovo‐Oxfordian (COx) argillite is the most concern for engineers. In this paper, a micromechanical‐based elasto‐viscoplastic model is proposed, and its numerical realization is our main object. The COx argillite is considered as a three‐phase composite consists of porous clay, quartz, and calcite. By assigning appropriate constitutive laws to those constituents, the macroscopic elasto‐viscoplastic behavior of the COx argillite is determined with an extended Hill's incremental approach. The numerical aspects includes (a) a new formulation is proposed for the plastic multiplier when adopting the overstress (Perzyna) model to define the viscoplastic strain. Meanwhile, a new formulation is also proposed to solve it within the framework of an implicit returning mapping scheme. (b) The corresponding consistent tangent moduli are strictly derived by extending the method proposed for solving plastic problems; (c) the efficiency of the proposed integration algorithms for the local constitutive equations and the homogenization procedure are validated, receptively, by a built‐in porous plasticity model of a commercial finite element (FE) program ABAQUS and by FE computations of a two‐phase unit cell; and (d) the proposed micromechanical model is finally applied to simulate experiment data in short‐term triaxial compression tests and long‐term triaxial creep tests. And the numerical results show that it is able to reflect the variation of the mechanical behavior with respect to the varied mineralogical compositions.