Thermal and Thermomechanical Analyses of WIPP (Waste Isolation Pilot Plant) Shaft Seals: Topical Report RSI-0324

摘要

Thermal and thermomechanical analyses provided information on the behavior and stability of concrete seals emplaced in a circular shaft. The two types of concrete considered were an expansive salt-saturated concrete for seals located in rock salt or other rock and an expansive freshwater concrete for seals located in nonsalt rock. Thermal analyses determined the temperature rise in the concrete and surrounding rock as a result of the exothermic hydration of the cement in the concretes. The thermomechanical analyses considered time-dependent elastic modulus, thermoelastic expansion, time-dependent chemically induced expansion, and creep of the concrete; thermoelastic behavior of the nonsalt rocks; and thermoelastic and creep behavior of the rock salt. Supplementary analyses determined the effects of pressure loading on a face of the seal as might result from a static brine head or the swelling of a bentonite backfill; the influence of using a reduced elastic modulus for the rock salt; and the effect of eliminating the chemical expansivity of the concrete. Results of interest were the development of radial stress in the seal, the magnitudes of tensile and shear stresses induced in the seal and rock, and the effect of bonding or lack of bonding between the seal and the surrounding rock. The chemical expansivity of the concrete was shown to be important for the development of radial stresses in the seal and at the contact between the seal and the surrounding rock. The shear stresses induced in the seal by the swelling pressure of bentonite become a concern if the radial stresses are not developed. 20 refs., 58 figs., 3 tabs. (ERA citation 13:011030)