A Viscoelastic, Viscoplastic, and Viscodamage Constitutive Model of Salt Rock

Based on the effective stress concept of continuum damage mechanics (CDM) and the assumption of a small deformation, a constitutive model of salt rock coupling viscoelasticity, viscoplasticity, and viscodamage is developed based on the Kelvin-Voigt model, Duvaut-Lions model and viscodamage model. The constitutive model is calibrated by experimental data of salt rock to determine the viscoelastic, viscoplastic, and viscodamage model parameters. The verification indicated that this constitutive model can reasonably model the primary creep, steady-state creep, accelerated creep in constant stress loading. Based on user material subroutine UMAT in Abaqus software, a three-dimensional finite element implementation of this constitutive model is realized. The constitutive model can effectively simulate mechanical responses including the long-term time-dependent deformation and damage evolution of geological bodies of salt rock and successfully conduct stability evaluation and failure analysis of cavern of large time span. This will provide a safety guarantee for underground energy storage.