Nonlinear analytical models for interfacial plug stresses in creeping salt formation

The disposal of high level nuclear waste material deep within the confines of a rock-salt formation is being considered for the safe disposal of radioactive material. Access boreholes, shafts, tunnels, and drifts used for transporting the waste material must be sealed after the waste has been stored. Expansive self-stressing concrete plugs are being field tested. Analytical and numerical simulation models are presented in this paper which predict the nonlinear time dependent behavior of an expanding plug in a creeping environment heavily dependent on the storage room temperature. Extensive sensitivity and parametric studies have been performed. These studies show that the interfacial strains between the concrete plug and surrounding rock-salt are largely influenced by: (a) the time dependent variation in the early modulus of concrete; (b) creep and shrinkage behavior of concrete; (c) creep and borehole convergence behavior of rock-salt; and (d) expansivity characteristics of the plug material