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

Abstract

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.