Consolidation and permeability of salt in brine

Abstract

The consotldatfcki and loss of permeability of salt crystal aggregates, importa.it in assessing the effects of water in salt repositories, has been studied as a function of several variables. The kinetic behavior was shatter to that often observed in sinter ing and suggested the following expression for the time dependence of the void fraction: • ft) • •«>)-W/fi)ln(1 • «/z(0) s) , where A and B are rate constants and z(0) is initial average particle size. With brine present, A and 4(0) varied linearly with stress. The initial void fraction was also dependent to some extent on the particle size distribution. The rate of consolidation was most rapid In brine and least rapid In the presence yf only air as the fluid. A brine containing 6 m MgC1 2 showed an Intermediate rate, presumably because of the greatly reduced ^ofubHity of NaCt. A substantial «all effect was Indicated by an observed increase in the void fraction of consolidated columns with distance from the top where the stress was applied and by a dependence of consolidation rate on the column height and radius. The distance through which the stress fell by a factor of e was estimeted to change Inversely as the fourth power of the column diameter. With increasing temperature (to 86*C), consolidation proceeded somewhat more rapkRy and the wail effect was reduced. The permeability of the columns dropped rapidly with consolidation, decreasing with about the sixth power of the void fraction. In general, extrapolation of the results to repository conditions confirms the eeif-eeaOng properties of bedded sett as a storage medium for radioactive waste.

Permeability of salt-crystal interfaces to brine

“…(1)] for the rate of consolidation of polycrystalline salt in brine. Such a similarity is consistent with the fact that the linear decrease of the void fraction with the logarithm of time persists to very low void fractions (Shor et al 1981), presumably to the point where the consolidation rate is determined by the decreasing permeability of the grain boundaries along which the brine must escape in order for consolidation to proceed. The raic at which brine is excluded from stressed specimens of halite that are almost fully consolidated is presently being investigated.…”

“…Previously we have reported a study of the consolidation of salt crystals in the presence of brine (Shor et al 1981). The procedure consisted of forming a settled bed of salt crystals from a suspension in saturated brine and then measuring the rate of consolidation and the decreasing permeability when the bed was stressed by a perforated piston.…”

Evaluation of potential crushed-salt constitutive models

“…Particle Size Shor et al [1981] performed a number of consolidation tests under uniaxial strain conditions. Based on these experimental results, they developed a model which included a strong dependence of consolidation rate on particle size.…”

“…Grain size is believed to be more important when moisture is present because densification through pressure solutioning is operative. To incorporate grain-size dependence, the form used by Shor et al [1981] and Spiers and Brzesowsky [1993] is used, and the grain-size effect (G) is given by:…”

Sealing of Boreholes and Underground Excavations in Rock

“…At a given stress the single most important parameter in the consolidation of granular salt is the presence of a small amount of water. Small amounts of water accelerate consolidation and the accompanying permeability decreases in comparison with dry granular salt (Zeuch and Holcomb, 1991;Holcomb and Shields, 1987;International Technology Corp., 1987;Shor, Baes and Canonico, 1981;Pfeifle, 1991}. The effects of other variables, such as particle size, are secondary and not as obvious.…”