Behaviour of saline frozen soils

A pile load test program carried out in Iqaluit, Northwest Territories, to provide design information for the Short Range Radar sites is described. The program consisted of testing 10 steel pipe piles with various surface modifications backfilled with clean sand and 4 Dywidag bars backfilled with Ciment Fondu™ grout. All tests were performed in saline permafrost. This paper describes the site conditions, installation procedures and pile uplift load testing procedures, and results of the pile load tests. The beneficial effect of modifications to the pile surface and backfill material is identified. The analysis and discussions of the results are presented in a companion paper. Key words : permafrost, saline, piles, load tests, field, in situ, capacity.

Field pile load tests in saline permafrost. I. Test procedures and results

Biggar¹,

Sego²

1993

The strength and deformation behaviour of model adfreeze and grouted piles in saline frozen soils

Biggar¹,

Sego²

1993

The results of a laboratory study to determine the influence of soil salinity, pile surface treatment, pile backfill material, and temperature on the adfreeze bond strength and deformation of model piles are presented. The influence of salinity and temperature on the adfreeze strength is shown to be related through the unfrozen water, and similar strength results were obtained at similar unfrozen water contents. Salinity in the backfill material of 10 and 30 ppt caused reductions in the adfreeze bond strength of 80–99%. Similar salinities within the native soil reduced its shear strength causing the location of the failure to change from the pile–backfill interface to the backfill – native soil interface when nonsaline backfill was used. Sandblasting of the pile surface to remove any surface coating resulted in adfreeze bond strengths two to three times greater than those measured on nonsandblasted piles. The use of cementitious grout to replace the sand slurry backfill resulted in greater pile load carrying capacity as the failure surface was transferred to the grout (backfill) – native soil interface instead of the pile–backfill interface. Use of backfill made from saline native soil cutting should be discouraged because of the detrimental effects of pore-fluid salinity on the adfreeze bond strength. Key words : frozen soil, saline, model pile, adfreeze, strength, deformation, grout, temperature.

Distribution of saline permafrost in the Northwest Territories, Canada

Hivon¹,

Sego²

1993

Saline permafrost has a detrimental impact on the performance of foundations. Increased pore-water salinity decreases the strength and increases the deformation susceptibility of permafrost and foundations installed in permafrost. A data base of the distribution of saline permafrost in the Northwest Territories shows high pore-water salinities beneath coastal communities and at locations along the upper Mackenzie Valley and within the Mackenzie Delta. Salinity of inland sites is usually low. High salinities are usually associated with ice-poor materials and are linked with previous marine submergence associated with glacial events. Key words : permafrost, saline distribution, measurements, Quaternary geology.