PILE LOAD TESTS IN SALINE PERMAFROST AT CLYDE RIVER, NORTHWEST TERRITORIES

Significant salt content in the pore phase of permafrost causes dramatic reduction in strength or bearing capacity. Previous experience with laboratory tests and limited field testing discussed in the Soviet literature indicate that creep rates can be accelerated many times and foundation bearing capacities reduced by factors of 2-3 if pore water salinities exceed 10-20 ppt. At Clyde River on the northwest coast of Baffin Island, pile load tests were carried out in 1982. A combination of high salinities and significant excess ice contents at some locations suggested that a limited program of pile load testing should be carried out to confirm or modify the initial pile loadings based on previously published material. No fully documented case history was available to support initial pile design loads. Three piles were subjected to loads of five different magnitudes for different durations. Creep settlement was initiated and persisted in all cases. Continuous curve fitting was carried out by computer, and the resulting smoothed strain rate plotted with time. The minimum settlement rates were compared with earlier predictions. They were generally somewhat faster than results from previous laboratory saline creep testing combined with theoretical pile design based on creep settlement. The tests highlight the dramatic reductions in foundation bearing capacity and acceleration in pile creep rates that can be expected in permafrost exhibiting significant pore water salinity. A simplified testing procedure suitable for laboratory or field testing is described.

• Corporate Authors:

  National Research Council of Canada

  1200 Montreal Road
  Ottawa, Ontario  Canada  K1A 0R6
• Authors:
  • Nixon, J F
• Publication Date: 1988-2

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 24-32
• Serial:
  • CANADIAN GEOTECHNICAL JOURNAL
  • Volume: 25
  • Issue Number: 1
  • Publisher: National Research Council of Canada

Subject/Index Terms

• TRT Terms: Creep; Load tests; Permafrost; Pore water; Saline soils; Structural tests; Support piles
• Old TRIS Terms: Pile tests
• Subject Areas: Bridges and other structures; Geotechnology; Highways; I42: Soil Mechanics;

Filing Info

• Accession Number: 00469043
• Record Type: Publication
• Files: TRIS
• Created Date: Jun 30 1988 12:00AM