Creep tests on clean and argillaceous salt from the Waste Isolation Pilot Plant

Abstract

Fifteen triaxial compression creep tests were performed on clean and argillaceous salt from the Waste Isolation Pilot Plant (WIPP). The temperatures in the tests were either 25°C or 100°C while the stress difference ranged from 3.5 MPa to 21.0 MPa. In ali tests, the confining pressure was 15 MPa. Test duration ranged from 23 to 613 days with an average duration of 300 days. The results of the creep tests supplemented earlier testing and were used to estimate two parameters in the Modified Munson-Dawson constitutive law for the creep behavior of salt. The two parameters determined from each test were the steady-state strain rate and the transient strain limit. These estimates we_e combined with parameter estimates deTLerminedfrom previous testing to study the dependence of both transient and steady-state creep deformation on stress difference. The exponents on stress difference determined in this study were found to be consistent with revised estimates of the exponents reported by other investigator,;. • This report was preparedby RFJSPECInc. underContract No. 05-7502 with SandiaNational Laboratories.

Reinvestigation into Closure Predictions of Room D at the Waste Isolation Pilot Plant

“…Munson et al (1989) chose to distinguish between clean and argillaceous salt based on the experiments in Senseny (1986). Similar di↵erences between clean and argillaceous salt were later found in Mellegard and Pfeifle (1993). Fig.…”

“…(1.12). The steady-state strain rates were Figure 4.4: Legacy clean and argillaceous salt creep experiments compared All experimental data points were were copied verbatim from Table 4-1 and 4-2 in Mellegard and Pfeifle (1993) multiplied by exp ⇥ Q 2 /R (1/T (1) 1/T (2) ) ⇤ , and the transient strain limits were multiplied by exp ⇥ c (T (1) T (2) ) ⇤ , where T (1) = 298 K, T (2) = 333 K, Q 2 /R = 4995 K, and c = 1.085 ⇥ 10 2 K 1 . (The values for Q 2 /R and c came from calibration 1A.)…”

“…Another potential reason for the increased creep in the legacy argillaceous salt is cores from one location at WIPP may behave di↵erently than cores from another location. Senseny (1986) and Mellegard and Pfeifle (1993) say the specimens were cored from the ribs of the experiment rooms at the WIPP. No further information is given, so the drill sites cannot be pinpointed as was done for the 2013 cores in Section 3.1.…”

The disturbed rock zone at the Waste Isolation Pilot Plant.

“…Early work focused on the characterization of the elastic and inelastic viscoplastic flow properties of salt (e.g., Hansen and Mellegard, 1977;Hannum, 1979, Hansen andMellegard, 1980;Senseny, 1986;Mellegard and Pfeifle, 1993 The phenomena associated with salt fracture were made obvious from observations in the WIPP underground (Section 4.6) and geophysical measurements (Section 4.7). Despite an acknowledged importance of salt damage to the WIPP repository, the DRZ was given a rather rudimentaq treatment in the compliance calculations.…”

Multimechanism-Deformation Parameters of Domal Salts Using Transient Creep Analysis

“…Because the creep databases for both the Weeks Island [Mellegard and Pfeifle, 1996;Munson and Ehgartner, 1997] and Avery Island [DeVries, 1988;Mellegard et al, 1983] domal salts are complete, there is no need to perform a transient analysis of the data. In these databases, a number of standard creep tests yield directly the values of the relevant parameters of steady state creep rate, transient strain limit, and initial value of the curvature.…”