Thermodynamic based model for coupled elastoplastic damage-healing behaviour of unsaturated geomaterials

The capacity for self-healing of fractures in geomaterials, especially clay, is a well-documented phenomenon that is important in many problems encountered in geotechnical and geo-environmental engineering (e.g., foundation design, slope stability, waste barrier systems, hydraulic fracturing). Several constitutive models that can account for damage and fracture of geomaterials have been proposed, many of which are formulated at microstructural scale with high computational costs that often preclude them from usage in engineering practice. In addition, mechanical constitutive laws describing healing (i.e., damage reversal) have been mainly developed for concrete and rock but not for soil.

A coupled elastoplastic-damage-healing constitutive model is presented in this paper to investigate the behaviour of geomaterials subjected to hydro-mechanical loadings. The mathematical formalism is presented within a continuum mechanics framework, with damaged-healed configuration defined through an energy equivalence hypothesis. Damage and healing evolution laws are also established within the framework of thermodynamics, taking into account the effect of plastic hardening, strain rate, stress ratio, suction hardening as well as confining pressure. The elastoplastic response of geomaterials is captured using a bounding surface plasticity model from critical state soil mechanics. Effects of damage, healing and suction are also accounted for by defining a proper hardening rule based on the consistency condition. The presented model's ability to simulate experimental results taken from the literature is assessed. Several examples are solved under different loading conditions in order to study the effect of damage-healing on the behaviour of unsaturated soils.