Creep behavior of bedded salt from southeastern New Mexico at elevated temperature

Results of a series of triaxial creep experiments conducted on bedded salt specimens from ERDA Hole 9 in southeastern New Mexico are presented. The purpose of the experiments was to measure creep response of salt at temperatures of 24, 70, and 1000C under confinement pressures of 0, 1500, 2000, 2500, and 3000 psi and differential axial stress levles of 1500, 3000, 4500, and 6000 psi. Test durations ranged from 15 minutes to over 500 hours. The specimens, obtained by recording 4-in.-dia cores in the axial direction, were nominally two inches in diameter and four inches in length. The crystal size ranged from very small to one-half inch diameter; the specimens contained various amounts of clay impurities. A total of 19 specimens were prepared of which 14 were tested. The collected data included axial and lateral strain, axial and confinement stresses, time and temperature. Periodically, axial stress was adjusted to account for specimen strain in order to maintain a constant differential stress. Frequency of the stress correction was dependent on the rate of deformation; two or more corrections in a 24-hour period were typical. Data were automatically recorded with a printer, manually recoded from the print-out to punched cards and reduced by means of a computer. A preponderance of the data was collected in the transient creep regime. In some tests specimen rupture occurred, while in others an accelerating creep rate brought the specimen in contact with the pressure vessel wall. Aslo, a considerable amount of data was collected during stress application to creep stress level