This report is an extension of the authors' earlier resistance-to-ground experiments. Here they supply additional information on the influence of salt-treated backfills around grounding electrodes for reducing resistance to ground. The results are based on observations made over several seasons of freezing and thawing at sites selected for their variations in grain size, ice content, and ground temperature. More than 20 test electrodes were monitored at two silt sites and one alluvial site. The diameter of the backfilled zones, the salt content, and the backfill material were varied for the electrode installations. In all cases salt backfilling reduced the resistance to ground, with 175 ohms being the lowest value obtained. Reductions varied from very small to an order of magnitude. Resistance also decreased over several seasons. Generally the greatest improvement and lowest values were obtained in the perennially frozen silt in interior Alaska. Data from colder silt suggest that salt backfilling will not be effective in arctic settings. Measurements at a partially thawed, coarse-grained site indicate that salt was moving much more rapidly (approximately give times as fast) away from the treated backfill than at the silt site in the CRREL permafrost tunnel. (Author)
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