A Damage Mechanics Treatment of Creep Failure in Rock Salt

Recent progress in the formulation of a constitutive model for describing coupled creep and damage development in rock salt is summarized. The constitutive model is based on the assumption that both dislocation slip and creep damage in the form of microcracks with possible wing-tips contribute to the macroscopic inelastic strain rate. The relevant kinetic equations, flow law, and damage evolution equation are presented. Evaluations are made of the coupled creep and fracture model against the measured creep response of clean salt from the Waste Isolation Pilot Plant (WIPP) site. In addition, the development of creep damage and the rupture of WIPP salt subjected to either triaxial compression or indirect tension have been analyzed to evaluate several creep rupture criteria.

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