Long-Term Pile Load Testing System Performance in Saline and Ice-Rich Permafrost

Abstract

A long-term pile load testing program was completed at two distant early warning (DEW) line sites; two piles were embedded into a tabular ice body, and three in a saline fine-grained soil. The piles were loaded in compression using a hydraulic cylinder system coupled with a large accumulator to maintain the load as the piles displaced. A self-contained data-logging system was utilized to record loads, hydraulic pressures, displacements, and temperatures for one year without interruption or intervention. Test durations varied from two months to three years, the longer tests requiring annual changing of the logger batteries and incremental increases to the pile load. The loading system worked well except in the instance where the accumulator was initially overfilled with oil. The data-acquisition system performed as designed, except when water leaked into the container through a poor seal. The grout-backfilled piles gave greater capacities than expected, particularly in saline permafrost. The soil slurry backfilled pile in ice behaved as predicted by current design guidelines.