ABSTRACT
Early attempts to predict the creep response of rock salt around underground rooms at the Waste Isolation Pilot Plant (WIPP) produced closure estimates that were one-third to one-fourth of values measured in situ. A subsequent study of the WIPP reference elastic secondary creep model used to make these predictions revealed that room closures and even closure rates could be increased by reducing the elastic constants. The WIPP elastic secondary creep law is used as the constitutive model for the salt. Attempts were made to determine new parameters for the UCP model that would provide good fits to both creep data and the stress relaxation data. The chapter concludes with a comparison of shaft closures computed with two unified creep plasticity (UCP) models, one with parameters determined from a fit to only constant stress laboratory creep data and the other with parameters obtained by fitting laboratory stress relaxation data in addition to the creep data.
