Hydrologic property alterations due to elevated temperatures at Yucca Mountain

Drying experiments were conducted on fifty core samples of welded tuff and fifty core samples of zeolitic, nonwelded tuff. Initially, all core samples were vacuum saturated, and weights and volumes were measured. The samples were dried in a relative humidity oven at 60 degrees C and 45 percent relative humidity. Sorptivity was measured to obtain information on flow properties. The samples from each type of tuff were divided into five sets of ten samples with similar mean porosities. Each sample set was subjected to a different drying temperature; 60, 105, 200, 300 or 400 degrees C with the fifth group left as a control. After drying, the samples were resaturated and all the measurements repeated. Calculated porosity, particle density, and sorptivity increased; and bulk density decreased with increasing temperature. Air and water permeability increased on the nonwelded tuff samples, however air permeability was unchanged for the welded tuff. All bulk properties recovered to the original values following drying, while the flow properties (sorptivity and air and water permeability) were permanently altered. At the completion of the flow measurements, one core from each temperature treatment, was cut into small disks. Water retention curves were measured on these disks (subsamples). There were no differences in measured water retention curves due to drying at different temperatures