Consolidation of the Waste Isolation Pilot Plant crushed salt/bentonite mixtures as a function of confining pressure and moisture content as compared with constitutive model predictions

Four hydrostatic consolidation tests were performed on crushed salt/bentonite mixtures to evaluate the influence of moisture on consolidation rate, permeability, and compressive strength. Specimens comprised 30 percent bentonite and 70 percent salt based on total dry weight. Brine was added to each specimen to adjust its total moisture content to between 3.5 and 10 percent (nominal) of the total dry weight. In the consolidation tests, each specimen was subjected to two stages of hydrostatic stress: 0.5 MPa and 3.45 MPa. During each stage, the pressure was maintained at a constant level and volumetric strain data were continuously logged. By using multiple stages, consolidation data were obtained at two pressures and the time required to consolidate the specimens to full saturation was reduced. Once full saturation was achieved, specimens were subjected to a final test stage in which the hydrostatic stress was reduced and a permeability test was performed. A steady flow permeability test was performed successfully on only one specimen and its permeability was determined to be 1.12 x 10-19 m2. An unconfined compressive strength test was conducted on one of the consolidated specimens and was found to be 1.66 MPa. A density model proposed by Sjaardema and Krieg was compared to the dry density data using parameter values established by Callahan and DeVries. The model fit the data best at intermediate moisture contents and low pressures. The model was also fitted to the data obtained in this study to determine additional parameter values