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Small quantities of brine trapped in ‘negative crystals’ (cavities) exist in most rock salt (halite) and have been found to migrate toward a heat source. The theory of Hoekstra and others on the migration of liquid inclusions in ice crystals was modified for predicting the migration rates of brine cavities in salt. The driving force for the migration is the difference in solubility between the warm and colder sides of the brine cavity. The theoretical model indicates that the migration rate is a function of temperature and is directly proportional to the temperature gradient. Calculated cavity migration rates for a 1°C/cm gradient ranged from about 0 at 20°C to 7.7 cm/yr at 300°C. The theoretical predictions were found to be in reasonable agreement with migration rates measured in the laboratory, although there was considerable spread in the experimental data. Specimens consisted of relatively pure salt crystals from the Hutchinson, Kansas, mine, about 2½ cm on a side, containing brine cavities between 2 and 10 mm in maximum dimension. Thirty‐one rate measurements (on twelve separate cavities) were obtained, covering the temperature range of 75°–244°C, with gradients ranging from 4 to 34°C/cm. Migration periods varied from about 20 to 358 hours, and the observed distances of migration ranged from 0.8 to 8 mm. The theoretical predictions also tended to confirm the approximate (but difficult to measure) rates of brine migration into a number of heated holes (salt wall temperatures up to 200°C) located in the Kansas mine.

Summary --Zusammenfassung --Résumé Deformation of Rock Salt in Openings Mined for the Disposal of Radioactive Wastes.With the storage of high-level radioaetive waste in salt struetures, unique mine stability problems will oeeur as a result of the elevated temperatures. To prediet flow in rock salt, seale models of salt pillars and their surrounding rooms were fabrieated from eores taken in the Carey salt mine, Lyons, Kansas. Tests were eondueted at temperatures of 22.5 e, 60 o , 100 °, and 200°C for axial loads of 2000, 4000, 6000, 8000, and 10000 psi at ca& temperature. These tests showed that marked inereases oceur in the rates of deformation of salt pillars at high loads and especially at elevated temperatures. For all eombinations of axial loads and temperatures, it was observed that there is initially a high rate of deformation that diminishes with time. Creep rates were found to eontinue to deerease even after more than 3 years of testing. An empirieM relationship between pillar deformarion, stress, temperature, and time was developed from the tests and is expressed as = 0.39.10 -aT T 9'5 o "%0 t -0"70, e = 1.30-:10 -37 T 9"5 a3.0 to.30 where » = strain rate (in./in./hr), « = eumulative deformation (im/in.), T = absolute temperature (°K), o = average pillar stress (psi), and t = time (hr).For eomparative purposes, model pillar tests were eonducted on samples of bedded salt, as welI as deine salt from six different mines in the United States and from the antielinM strueture of the Asse II salt mine in Northeast Germany. In general, the deformational behavior for the various types of salt was similar at room temperature as well as at elevated temperature even though seine variations in the rates of deformation were observed.From model tests it was also observed that greatly aeeelerated rates of deformation will oeeur in exeavated eavities where thin shale beds oeeur in the pillars at the roof and floor interfaees. Sinee the sha!cs serve as frietion redueers, effeetive eonfining stresses in the roof and floor are not transmitted into the pillars; thus the pillars under these eonditions are weaker than where shale partings are not present at the tops and bottoms of the pillars. Verformung von Steinsalz in Schäehten zur Déformation du sei gemme dans des eavités minières pour des déchets radioaetifs.Lots du stockage des déchets de haute radioactivité dans les formations géologiques de se] gemme los températures élevées causent des problèmes spéciaux de stabilité. Pour prévoir l'écoulement dans los formations de sel gemme on a construit des modèles réduits de pi]iers de sel ~ partir de carottes obtenues dans la mine de sel Carey ä Lyons, Kansas. On a fait des essais ä des températures de 22,50 60 °, 100 ° et 200°C, pour des charges axiales de 2000, 4000, 6000, 8000, 10000 psi ä chaque température. Ces essais ont montré que les hautes charges augmentent sensiblement les vitesses de déformation, en particulier aux températures élevées. Pour toutes los combinaisons de charges axiales et de températures, on a observé...

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