Influence of Geological and Environmental Factors on the Reconsolidation Behavior of Fine Granular Salt

Understanding the consolidation behavior of granular salt is of great significance for salt cavern repository design and the corresponding long-term safety assessments. To evaluate the influence of environmental and geological factors on the reconsolidation behavior of fine granular salt, a series of orthogonal array design experiments were performed. The experimental results showed that temperature, compressive stress, moisture content and compression time had significant impacts on the compaction properties of granular salt. The compressive stress exerted the greatest impact on porosity of the granular salt, which decreased the porosity. An increase in moisture content (within 3%) in the granular salt sample substantially reduced the porosity of the sample, whereas this effect was limited when moisture exceeded 3%. In the process of granular salt compaction, all of the deformation mechanisms were temperature dependent. The correlation between porosity and permeability of the dried compacted salt samples was independent of the environmental and geological factors during the compaction of the granular salt. The use of granular salt with a smaller particle size in the compacted salt backfill can improve its sealing performance. In the transient loading stage of granular salt compaction, the porosity decreased rapidly under stress to form a denser layer, which was mainly accomplished by particle rearrangement and cataclastic flow. However, in the constant-load creep stage, the additional porosity reduction was dominated by grain boundary processes and crystal plasticity mechanisms, including dislocation creep, pressure-solution creep and recrystallization.